Cambridge Lower Secondary
Science
LEARNER’S BOOK 7
Mary Jones, Diane Fellowes-Freeman & Michael Smyth
Second edition
Digital access
www.frenglish.ru
Cambridge Lower Secondary
Science
LEARNER’S BOOK 7
Mary Jones, Diane Fellowes-Freeman & Michael Smyth
www.frenglish.ru
University Printing House, Cambridge CB2 8BS, United Kingdom
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education, learning and research at the highest international levels of excellence.
www.cambridge.org
Information on this title: www.cambridge.org/9781108742788
© Cambridge University Press 2021
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no reproduction of any part may take place without the written
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First published 2012
Second edition 2021
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ISBN 978-1-108-74278-8 Paperback
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www.frenglish.ru
Introduction
Introduction
Welcome to Stage 7 of Cambridge International Lower Secondary Science.
We hope this book will show you how interesting and exciting science can be.
Science is everywhere. Everyone uses science every day. Can you think of
examples of science that you have seen or used today?
Have you ever wondered about any of these questions?
•
What am I made of ?
•
Where do all the dead plants, animals and their waste disappear to?
•
Why does frozen water behave differently to liquid water?
•
What happens in a chemical reaction?
•
What is electricity?
•
How did the planets form around the Sun?
You will work like a scientist to find answers to these questions and
more. It is good to talk about science as you investigate and learn.
You will share your ideas with classmates to help them understand,
and listen to them when you need reassurance. You will reflect on
what you did and how you did it, and ask yourself: ‘would I do things
differently next time?’
You will practise new skills and techniques, check your progress
and challenge yourself to find out more.
You will make connections between the different sciences and
how they link to maths, English and other subjects.
We hope you enjoy thinking and working like
a scientist.
Mary Jones, Diane Fellowes-Freeman, Michael Smyth
iii
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Contents
Contents
Page Unit
Science
strand
Thinking and working
scientifically strand
Science in context
1
1
6
10
15
1 Cells
1.1 Plant cells
1.2 Animal cells
1.3 Specialised cells
1.4 Cells, tissues and organs
Biology:
Structure and
Function
Carrying out scientific
enquiry
Models and
representations
Discuss how scientific
knowledge is developed
through collective
understanding and
scrutiny over time
21
21
28
34
39
44
Chemistry:
Materials and
their Structure
Earth and
Space: Cycles
on Earth
Earth and
Space: Planet
Earth
Models and
representations
Carrying out scientific
enquiry
Scientific enquiry:
analysis, evaluation
and conclusions
Discuss how scientific
knowledge is developed
through collective
understanding and
scrutiny over time
50
57
2 Materials and their structure
2.1 Solids, liquids and gases
2.2 Changes of state
2.3 Explaining changes of state
2.4 The water cycle
2.5 Atoms, elements and the
Periodic Table
2.6 Compounds and formulae
2.7 Compounds and mixtures
68
68
78
84
90
98
104
110
3 Forces and energy
3.1 Gravity, weight and mass
3.2 Formation of the Solar System
3.3 Movement in space
3.4 Tides
3.5 Energy
3.6 Changes in energy
3.7 Where does energy go?
Physics:
Forces and
Energy
Carrying out scientific
enquiry
Models and
representations
Describe how people
develop and use
scientific understanding,
as individuals and
through collaboration,
e.g. through peer review
120
4 Grouping and identifying
Biology: Life
organisms
processes
4.1 Characteristics of living organisms
4.2 Viruses
4.3 What is a species?
4.4 Using keys
4.5 Constructing keys
Models and
representations
Carrying out scientific
enquiry
Evaluate issues which
involve and/or require
scientific understanding
Discuss how science
can have a global
environmental impact
5 Properties of materials
Chemistry:
Materials and
5.1 Metals and non-metals
5.2 Comparing metals and non-metals their structure
5.3 Metal mixtures
5.4 Using the properties of materials
to separate mixtures
5.5 Acids and alkalis
5.6 Indicators and the pH scale
Carrying out scientific
enquiry
Models and
representations
Describe how science is
applied across societies
and industries, and in
research
120
123
127
131
136
144
144
150
154
162
166
172
iv
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Contents
Page Unit
Science
strand
Thinking and working
scientifically strand
Science in Context
185
185
195
204
209
215
6 Earth physics
6.1 Sound waves
6.2 Reflections of sound
6.3 Structure of the Earth
6.4 Changes in the Earth
6.5 Solar and lunar eclipses
Physics: Light
and Sound
Earth and
Space: Planet
Earth
Scientific enquiry:
Evaluate issues which
purpose and planning involve and/or require
Carrying out scientific scientific understanding
enquiry
Scientific enquiry:
analysis, evaluation
and conclusions
Models and
representations
226
226
231
237
242
7 Microorganisms in the
environment
7.1 Microorganisms
7.2 Food chains and webs
7.3 Microorganisms and decay
7.4 Microorganisms in food webs
Biology:
Structure and
Function
Models and
representations
Scientific enquiry:
purpose and planning
Carrying out scientific
enquiry
Scientific enquiry:
analysis, evaluation
and conclusions
Describe how science is
applied across societies
and industries, and in
research
Evaluate issues which
involve and/or require
scientific understanding
Describe how people
develop and use
scientific understanding,
as individuals and
through collaboration,
e.g. through peer review
252
252
261
269
274
8 Changes to materials
8.1 Simple chemical reactions
8.2 Neutralisation
8.3 Investigating acids and alkalis
8.4 Detecting chemical reactions
Chemistry:
Properties of
materials
Chemistry:
Changes to
materials
Scientific enquiry:
purpose and planning
Carrying out scientific
enquiry
Scientific enquiry:
analysis, evaluation
and conclusions
Models and
representations
Describe how science is
applied across societies
and industries, and in
research
287
287
292
297
303
310
9 Electricity
Physics:
Electricity and
9.1 Flow of electricity
magnetism
9.2 Electrical circuits
9.3 Measuring the flow of current
9.4 Conductors and insulators
9.5 Adding or removing components
Scientific enquiry:
purpose and planning
Scientific enquiry:
analysis, evaluation
and conclusions
Models and
representations
Carrying out scientific
enquiry
Describe how science is
applied across societies
and industries, and in
research
v
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How to use this book
How to use this book
This book contains lots of different features that will help your learning. These are explained below.
This list sets out what you will learn in each
topic. You can use these points to identify the
important topics for the lesson.
In this topic you will:
•
begin to learn about cells
•
•
make a model of a plant cell
•
use a microscope to look at plant cells.
Getting started
This contains questions or activities to help find
out what you know already about this topic.
Plants and animals are living organisms. They are made of units
called cells.
With a partner, think about answers to these questions:
•
How big do you think a cell is?
•
How can we see cells?
•
Can you describe what a cell looks like?
Be ready to share your ideas with the class.
Important words are highlighted in the text
when they first appear in the book. You will
find an explanation of the meaning of these
words in the text. You will also find definitions
of all these words in the Glossary
and Index at the back of this book.
You will have the opportunity to practise and
develop the new skills and knowledge that
you learn in each topic. Activities will involve
answering questions or completing tasks.
Key words
stain
1.2 Plant cells
Activity 1.3.1
Sap vacuole: This is large, fluid-filled space inside a plant cell. The liquid
and function in animal cells
inside is a solution of sugarsStructure
and other
substances dissolved in water.
Work with a partner.
The solution is called cell sap.
Here is the start of a table that you can use to summarise how each kind of specialised
Chloroplast: Plant cells that animal
are incell
theis sunlight
contain
adapted tooften
carry out
its function.
chloroplasts. This is where plants make their food. Chloroplasts look
cell.substance called chlorophyll.
green because they contain ablood
green
Mitochondrion: All plant cells have mitochondria (singluar:
Next, add entries for a neurone and a ciliated cell. Remember to give your table a title.
mitochondrion). Inside mitochondria, energy is released from food.
Questions
When you are ready, copy your completed table onto a large sheet of paper, ready to
be displayed.
1
of plant
cell
Function
of cell
Look at the photograph Name
of the
cells.
What
do you Specialised
think the
structure
little green circles inside the cells are? Why are they green?
What is
their function?
How this helps the
cell to carry out
its function
2
blood cell
has haemoglobin
Describe four differencesred
between
a celltransports
wall and a cell membrane.
haemoglobin
carries oxygen
oxygen
in its cytoplasm
How have your tried to remember the difference between a cell wall
and a cell membrane? How successful do you think you have been?
Neurone
Think like a scientist
Making a model of a plant cell
In this activity, you will make a model to represent a cell. You will then think about the
strengths and limitations of your model.
This provides an opportunity
for you to practise and develop
scientific enquiry skills with a
partner or in groups.
Here is a list of materials and objects you could use to make your model.
• transparent boxes • cardboard boxes • small and large plastic bags filled with water
• green peas or green beads
• cling film (transparent food wrap)
• cardboard boxes of various sizes • empty plastic bags • purple grapes
• some green grapes • Plasticine®
In your group, decide how you can use some of these materials and objects to make a
model of a plant cell. Then make your model.
Be ready to explain your model to others.
Questions
1
Compare your model cell with the models made by other groups.
Are there are any features of your model that are better than theirs?
Are they any features of other groups' models that are better than yours?
2
Discuss how well your model cell represents a real plant cell.
7
vi
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How to use this book
1 Cells
1 Cells
5
Young plants and animals get bigger. This is called ……………… .
a things
scientist:
Self-assessment
6 Think
All like
living
break
down some of the food they eat, to provide
them
withhow
energy.
Think
about
youThis
did happens
this task.in a process called ……………… .
7 ForMost
things
can change
theyourself:
shape and position of their
eachliving
of these
statements,
rate
bodies. This is called ………………… .
After completing an activity, this provides you
with the opportunity to either assess your own
work or another student’s work.
Activity 1.1
Is aif car
youalive?
think you
if you did it quite
did
it veryshows
well, a car. well, or needed
The
picture
with no help
some help
Here are some facts about cars.
•
•
•
•
This contains questions that ask you to look
back at what you have covered and encourages
you to think about your learning.
•
••
if you didn't do
it all, or needed
a lot of help
Cars
fuel of
and
I cut ause
piece
theoxygen.
inside layer of onion that was about
1 cm square.
Inside
the engine of the car, the fuel
and
to of
make
I wasoxygen
able toprovide
spread energy
the piece
onion flat in the
the
dropcar
ofmove.
water.
The
produces
waste
gases,without getting
I putengine
the cover
slip over
the onion
including
carbon dioxide. These are
any air bubbles.
given
off in the
of the
car.
I saw onion
cellsexhaust
down the
microscope
Some
have
sensors.
For
example,
they
sense
• cars
Write
down
one
thing that
didIreally
well
in can
this
I focused
the
microscope
soyou
that
could
see
theactivity.
cells when
it
is •dark
and
turn
the
light
Write
down
one
thing
thaton
youautomatically.
will try to do much better next
really
clearly
Questions time. How will you do this?
1
In your group, make a list of similarities between a car and
Summary
living checklist
things.
2
I can name
structuresbetween
in a plantacell,
what
Make
a listall
of the
differences
car and
anddescribe
living things.
they do
I can make a model of a plant cell, and discuss its strengths
and limitations
Summary
checklist
I can use a microscope to look at plant cells
I can list the seven characteristics of living things
This list summarises the important material that
you have learnt in the topic.
I can describe the meaning of each of these characteristics
1.2 Plant cells
At the end of each unit, there
is a group project that you can
carry out with other students.
This will involve using some of
the knowledge that you developed during the unit. Your
project might involve creating
or producing something, or
you might all solve a problem
together.
Project: Cells discovery timeline
This project is about how scientific knowledge gradually develops over time. You are
going to work in a group to do research, and then use your findings to help to make a
time line.
Science never stays still. When one scientist makes a new discovery, this suggests new
questions that other scientists can investigate.
You are going to help to produce a timeline. The timeline will show how scientists
gradually discovered that
4 all living things are made of cells.
10
Here are some of the important steps that occurred. Your teacher will allocate one or two
of these steps to your group. You will then help to find out more about these steps, and
produce an illustrated account of what happened. Try to include an explanation of how
the work of earlier scientists helped this step to take place.
1625 Galileo Galilei builds the first microscope.
1665 Robert Hooke looks at cork (from tree bark) through a microscope, and describes
little compartments that he calls cells.
1 1670
Cells Anton van Leeuwenhoek improves the microscope and is able to see
living cells in a drop of pond water.
1833 Robert Brown discovers the nucleus in plant cells
These questions look back at
some of the content you learnt
in each session in this unit. If
you can answer these, you are
ready to move on to the next
unit.
1838 Matthias Schleiden proposed that all plant tissues are made of
cells. Theodor Schwann proposed that is also true of animal cells.
Check your Progress
1845 Carl Heinrich Braun proposed that cells are the basic unit of all life.
1
Different cells have different functions.
Rudolf Virchow
says
all cells
only
arise
from
other describes.
cells.
1855 Choosing
from this
list,that
name
the cell
that
each
function
red blood cell
2
root hair cell
palisade cell
a
Moves mucus up through the airways.
b
Absorbs water from the soil.
c
Makes food by photosynthesis.
nerve cell
ciliated cell
[3]
The diagram shows an animal cell.
insert new diagram of
animal cell; label A to cell
membrane, label B to
cytoplasm, label C to nucleus,
label D to mitochondrion
3
a
Name the parts labelled A, B, C and D.
b
Describe two ways you can tell that this is an animal cell and not a plant cell.
The diagram shows a plant cell.
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[4]
vii
[2]
11
1
Cells
1.1 Plant cells
In this topic you will:
•
begin to learn about cells
•
find out about the parts of a plant cell, and what they do
•
make a model of a plant cell
•
use a microscope to look at plant cells.
Getting started
Key words
Plants and animals are living organisms. They are made of units
called cells.
cell
cell membrane
cell wall
cellulose
chlorophyll
chloroplast
cytoplasm
magnify
mitochondria
nucleus
sap vacuole
With a partner, think about answers to these questions:
•
How big do you think a cell is?
•
How can we see cells?
•
Can you describe what a cell looks like?
Be ready to share your ideas with the class.
2
2
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1.1 Plant cells
Cells
If you study a plant by observing part of it
through a microscope, you will see that it
is made up of a very large number of tiny
‘boxes’. These are called cells. All living
organisms are made of cells.
Cells are so small that you cannot see them
with your eyes alone. The photograph of the
plant cells was taken through a microscope.
The microscope magnifies the view of the
cells, so that they look much bigger than they
really are.
one cell
Part of a leaf seen through a microscope
Parts of a plant cell
The diagram shows a plant cell from a leaf.
cell wall
Every plant cell has a cell wall. The cell wall is
strong and stiff. It holds the plant cell in
shape. Plant cell walls are made of a substance
called cellulose.
sap vacuole
This is a large, fluid-filled space inside
a plant cell. The liquid inside it is a
solution of sugars and other substances
dissolved in water. The solution is
called cell sap.
cell membrane
All cells have a cell membrane. The cell
membrane is very thin and flexible. It is like
the thin skin of a soap bubble. It lies along the
inner edge of the cell wall. The cell membrane
controls what goes in and out of the cell.
chloroplast
Plant cells that are in the sunlight often
contain chloroplasts. This is where
plants make their food. Chloroplasts
look green because they contain a
green substance called chlorophyll.
cytoplasm
All cells have cytoplasm. Cytoplasm is like clear
jelly. Chemical reactions happen inside the
cytoplasm. These reactions keep the cell alive.
mitochondrion
All plant cells have mitochondria
(singular: mitochondrion). Inside
mitochondria, energy is released
from food.
nucleus
Most cells have a nucleus. The nucleus controls
the activities of the cell.
Diagram of a leaf cell
Questions
1
Look at the photograph of the plant cells on this page.
What do you think the little green circles inside the cells are?
Why are they green? What happens inside them?
2
Describe four differences between a cell wall and a cell membrane.
3
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1 Cells
How have you tried to remember the difference between a cell wall
and a cell membrane? How successful do you think you have been?
Think like a scientist
Making a model of a plant cell
In this task, you will make a model to represent a plant cell. You will then think about the
strengths and limitations (weaknesses) of your model.
Here is a list of materials and objects you could use to make your model.
•
transparent boxes
•
cardboard boxes
•
small and large plastic bags filled with water
•
green peas, green beads or green grapes
•
transparent food wrap
•
empty plastic bags
•
purple grapes
•
coloured modelling material
In a group of three or four, discuss how you can use some of these materials and objects
to make a model of a plant cell. Then make your model.
Be ready to explain your model to others.
Questions
1
Compare your model cell with the models made by other groups.
Are there are any features of your model that are better than those in the other
groups’ models?
Are there any features of other groups’ models that are better than yours?
2
Discuss how well your model cell represents a real plant cell.
4
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1.1 Plant cells
Microscopes
Scientists who study living organisms
often use microscopes to help them
to see very small things.
eyepiece
coarse focussing knob
fine focussing knob
high-power objective lens
medium-power objective lens
low power-objective lens
microscope stage
The diagram shows a microscope.
Look at a real microscope and find
all of these parts on it.
mirror
A microscope
Think like a scientist
Looking at plant cells through a microscope
This task gives you practice in using scientific equipment and doing practical work safely.
You will need:
a microscope, a microscope slide, a cover slip, a piece of onion bulb, tweezers (forceps),
a small sharp knife, a dropper pipette, a small container of water
1
Collect a small piece of onion. Cut out a piece about 1 cm square.
2
Use a dropper pipette to put a small drop of water into the middle of a clean
microscope slide.
3
Very carefully, peel the thin layer from the inside of your piece of onion.
4
Gently push the layer into the drop of water on the slide. Spread it out as flat as you
can.
5
Collect a very thin piece of glass called a cover
slip. (Take care – cover slips break very easily!)
Gently lower the cover slip over your piece of
onion on the slide. Try not to get air bubbles
under the cover slip.
6
Turn the objective lenses on the microscope
until the smallest one is over the hole in
the stage.
7
Put the slide onto the stage of the microscope,
with the piece of onion over the hole.
5
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1 Cells
Continued
8
Look down the eyepiece. Slowly turn the focussing knob to move the lens away from
the slide. Stop when the piece of onion comes into focus.
9
Make a drawing of some of the cells you can see.
Questions
1
Suggest why the cells from the onion do not look green.
2
Describe any difficulties you had with this activity. How did you solve them?
Self-assessment
Think about how you did this task.
For each of these statements, rate yourself.
if you think you did
it very well, with
no help
if you did it
quite well, or needed
some help
if you didn't do it all,
or needed a lot
of help
•
I cut a piece of the inside layer of onion that was about 1 cm square.
•
I was able to spread the piece of onion flat in the drop of water.
•
I put the cover slip over the onion without getting any air bubbles.
•
I saw onion cells down the microscope.
•
I focussed the microscope so that I could see the cells really clearly.
•
Write down one thing that you did really well in this activity.
•
Write down one thing that you will try to do much better next
time. How will you do this?
Summary checklist
I can name all the structures in a plant cell, and describe what
they do.
I can make a model of a plant cell, and discuss its strengths
and limitations.
I can use a microscope to look at plant cells.
6
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1.2 Animal cells
1.2 Animal cells
In this topic you will:
•
find out how animal cells differ from plant cells
•
use a microscope to look at some animal cells.
Getting started
Key words
There are five parts of a plant cell with names beginning with the
letter c.
stain
Make a list of these five parts. Think about how you can
remember what each of the words means.
Be ready to share your ideas.
7
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1 Cells
Parts of an animal cell
All animals are made of cells.
You are an animal, and your
body is made of cells. No one
knows exactly how many cells
there are in a person. One
estimate is about 100 trillion.
That is 100 000 000 000 000 cells.
cell membrane
cytoplasm
mitochondrion
nucleus
Animal cells are similar to plant
cells in several ways. They have
a cell membrane, cytoplasm and
a nucleus.
An animal cell
Think like a scientist
Looking at animal cells through a microscope
This task gives you more practice in using scientific equipment safely.
You will need:
a microscope, a microscope slide, a cover slip, a cotton bud,
some methylene blue, a dropper pipette
1
2
Very gently rub the cotton bud along
the inside of your cheek. This will collect
some loose cells.
Rub the cotton bud on the surface of a
clean microscope slide. You will not be
able to see the cells yet, because they are
so small.
New version of this with Zara's hair
tied up was supplied in July.
AW_U1_WB_06 is suitable,
even though it seems allocated
to the Workbook.
Tech-Set:- AW_U1_WB_06 is a
black and white version of the
same artwork! Please advise
3
Use a dropper pipette to add a drop of
methylene blue to the cells. Methylene blue is a dye that will
stain the cells blue, making them easier to see.
4
Carefully lower a cover slip over the drop of blue stain.
5
Put the smallest objective lens over the stage.
6
Put the slide onto the stage, with the part you want to look at over the hole in the stage.
7
Looking from the side, turn the focussing knob until the lens is close to the slide.
8
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1.2 Animal cells
Continued
8
Look down the eyepiece. Slowly turn the focussing knob to move the lens upwards.
Stop when you can see the cells.
9
Turn the lenses until a larger one is over the stage. Look down the eyepiece.
You should be able to see a more magnified view of the cells.
10 Make a drawing of one or two of the cells you can see. Label your drawing.
Questions
1
The photographs show some cells, seen through a microscope.
For each photograph, decide whether the cells are plant cells or
animal cells. Explain your decision.
2
Think about the model of a plant cell that you made.
What would you change to make it into a model of an animal cell?
Activity
Building up pictures of plant and animal cells
You will need:
•
fifteen cut-out oval pieces of card or paper, each about 1 cm long, five coloured
red and ten coloured green
•
one cut-out circular piece of grey card or paper, about 1 cm in diameter
•
long pieces of string or wool
•
a long piece of wide tape
•
glue or double-sided sticky tape
•
a very large sheet of paper
9
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1 Cells
Continued
1
In a group of two or three, use the materials to build a picture of a plant cell. It is up to
your group to decide exactly how to use the materials to make your picture. You may
not want to use all of the materials.
2
Ask your teacher, or other people in your class, to check that you have put all the right
pieces in the right places.
3
Now remove some of the pieces, to change your picture into an animal cell.
Self assessment
Compare your picture with the pictures made by other groups.
What differences are there between them?
Now that you have seen the other pictures, is there anything you would like to change in yours?
•
What have you done that helps you to remember the
differences between animal cells and plant cells?
•
Do you think that you can always decide whether a picture
shows an animal cell or a plant cell? What is the most important
feature to look for?
Summary checklist
I can use a microscope to look at animal cells.
I can describe similarities and differences between plant cells and
animal cells.
I can decide whether a picture of a cell shows an animal cell or a
plant cell, and give reasons.
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1.3 Specialised cells
1.3 Specialised cells
In this topic you will:
•
learn about some specialised animal and plant cells
•
explain how the structure of these specialised cells helps
them to carry out their functions.
Getting started
Key words
With a partner, think of a suitable way to complete each
sentence.
absorb
adapted
axon
capillary
cilia
ciliated cell
dendrite
function
haemoglobin
mucus
neurone
palisade cell
pigment
red blood cell
root hair cell
specialised
•
Cell membranes …
•
Cell walls …
•
A nucleus …
•
Chloroplasts …
Be ready to share your ideas with the rest of the class.
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1 Cells
Some specialised animal cells
Not all of the cells in your body are the same. There are many different
kinds of cell in your body. Each kind of cell has a particular function.
The function of a cell is the job that it does, or the role that it plays.
Each cell is specialised to carry out its function. This means that it
has a structure that helps it to do its function really well. The cell is
adapted to carry out its function.
The diagrams show three kinds of specialised cell in the human body.
Red blood cells are smaller than most other cells in the body.
This allows them to get through tiny blood capillaries, so they
can deliver oxygen to every part of the body.
The cytoplasm contains a red pigment (colour) called haemoglobin.
This carries oxygen around the body.
The cell has no nucleus. This leaves more space for haemoglobin.
Neurones carry electrical signals from one part of the
body to another. They help all the different parts of
the body to communicate with each other. For example,
they can carry signals from the brain to muscles, to
make the muscles move.
nucleus
cytoplasm
Red blood cells
cytoplasm
cell membrane
The axon is a very long strand of cytoplasm.
Electrical signals can travel along this very quickly.
Dendrites are short strands of cytoplasm that collect
electrical signals from other nearby nerve cells.
cell membrane
dendrite
axon
Neurones
Ciliated cells have tiny threads along one edge,
like microscopic hairs. These are called cilia. The cilia can move.
One place in the body that contains ciliated cells is the lining of the
tubes leading from your mouth to your lungs.
Other cells in this lining make a sticky substance called mucus.
When you breathe in, the mucus traps dust and bacteria in
the air, to stop them going into your lungs. The cilia sweep
the mucus up to the back of your mouth and you swallow it.
Questions
1
List two things that red blood cells, neurones and ciliated cells
have in common.
2
How can you tell that all of these three cells are animal cells,
not plant cells?
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cilia
cell membrane
nucleus
cytoplasm
Ciliated cella
1.3 Specialised cells
Activity 1.3.1
Structure and function in animal cells
Work with a partner.
Here is the start of a table that you can use to summarise how each kind of specialised
animal cell is adapted to carry out its function.
Copy the start of the table onto a piece of paper. Then complete the entries for the red
blood cell.
You could include a small drawing of a red blood cell underneath its name in the first column.
Next, add entries for a neurone and a ciliated cell. Remember to give your table a title.
When you are ready, copy your completed table onto a large sheet of paper, ready to
be displayed.
Name of cell
Function of cell
Specialised
structure
How this helps the
cell to carry out
its function
red blood cell
transports
oxygen
has haemoglobin
in its cytoplasm
haemoglobin
carries oxygen
Neurone
Some specialised plant cells
Plants also contain specialised cells. Here are two examples.
Root hair cells are found on the outside of plant roots.
Their function is to absorb (soak up) water from the soil.
Each cell has a long, thin extension that allows water to move easily
from the soil into the cell.
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1 Cells
cell wall
nucleus
cell membrane
cytoplasm
large vacuole
with cell sap
A root hair cell
Palisade cells are found in the leaves of plants. Their function is to
make food by photosynthesis.
They have a lot of chloroplasts containing chlorophyll.
The chlorophyll absorbs energy from sunlight, which is used to help
the plant make food.
cell wall
cell membrane
mitochondrion
cytoplasm
chloroplast
nucleus
A palisade cell
Questions
3
Suggest why root hair cells do not contain chloroplasts.
4
Water moves through several parts of the root hair cell, as it goes
from the soil into the sap vacuole. List these parts, in order.
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1.3 Specialised cells
Activity 1.3.2
Structure and function in plant cells
Make a table to summarise how the structures of the two kinds of specialised plant cell are
related to their functions.
Peer assessment
Exchange your table with a partner.
For each of these statements, rate your partner’s work.
if you think they
did it very well
if they did it quite well, but it if they didn't do it all, or it
could be improved
needs a lot of improvement.
•
They made a clear table with ruled lines.
•
They gave the columns in the table headings to make clear what each one shows.
•
They headed the rows in the table with the names of the two kinds of plant cell.
•
They wrote short, very clear descriptions of how the cell is specialised.
•
The table is very clear and you can understand it easily.
Summary checklist
I can name three kinds of specialised animal cell, and two kinds of
specialised plant cell.
I can explain how the structure of each kind of specialised cell is
related to its function.
I can design and construct a table to summarise information.
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1 Cells
1.4 Cells, tissues and organs
In this topic you will:
•
find out about tissues, organs and organ systems in living
organisms
•
recognise and name human organs that are part of different
organ systems.
Getting started
Draw an outline of a human body.
Sketch and label each of these organs on the outline.
brain heart stomach intestine lungs
Key words
ciliated epithelium
lower epidermis
onion epidermis
organ
organ system
organism
palisade layer
spongy layer
tissue
upper epidermis
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1.4 Cells, tissues and organs
Tissues
Living things, including animals and plants, are called organisms. There
are many different kinds of cell in an animal or a plant. Most of them
are specialised to carry out a particular activity. Usually, many cells of
the same kind are grouped together.
A group of similar cells, which all work together to carry out a
particular function, is called a tissue.
The diagrams show a tissue from a plant, and a tissue from an animal.
This is a diagram of a tissue from inside an onion. It is called an onion
epidermis. This tissue covers the surface of the layers inside the onion.
Onion epithelium
This is a diagram of ciliated epithelium – the tissue that lines the tubes
leading down to our lungs. The cilia all wave together, like grass in the wind.
cilia
nucleus
Ciliated epithelium
Questions
1
What is the function of the ciliated epithelium tissue?
(Think about the function of a ciliated cell.)
2
The word ‘tissue’ has an everyday meaning and a different scientific
meaning. Write two sentences, one using the word ‘tissue’ with
its everyday meaning, and one using the word ‘tissue’ with its
scientific meaning.
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1 Cells
This is part of a leaf, cut open. A leaf is a plant organ,
Organs and organ
systems
and contains
several different kinds of tissue.
The bodies of plants and
animals contain many different
parts, called organs. For
example, your organs include
your brain, heart and muscles.
Plants’ organs include leaves,
roots and flowers.
Each organ is made up of
several different kinds of tissue,
working together. For example,
your brain contains neurones,
and also several other kinds of
cell. A plant root contains root
hair cells, and also several other
kinds of cell.
upper epidermis
palisade layer
spongy layer
lower epidermis
This is part of a leaf, cut open. A leaf is a plant organ, and contains several
different kinds of tissue.
Organs also work together.
A set of organs that all
work together to carry out the same function is called an organ system.
Activity 1.4.1
Organs and systems in humans
Your task is to find out the names and functions of the different organs that are part of
one system in the human body.
Choose from: digestive system, circulatory system, respiratory system or skeletal system.
When you have found this information, decide how to display it. Perhaps you could
make a presentation, or a large drawing with labels and descriptions.
Question
3
Copy and complete each sentence, using words from the list.
organism tissue organ organ system
A group of similar cells is called a
.
An
is a structure made of many different tissues.
An
is a group of organs that carry out a particular function.
An
is a living thing. It may contain many different
organ systems, organs and tissues.
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1.4 Cells, tissues and organs
Summary checklist
I can give examples of tissues and organs in animals and plants.
I can explain the meanings of the words tissue, organ and organ system.
Project: Cells discovery timeline
This project is about how scientific knowledge
gradually develops over time. You are going to
work in a group to do research, and then use
your findings to help to make a timeline.
Science never stays still. When one scientist makes a
new discovery, this suggests new questions that other
scientists can investigate.
You are going to produce a timeline. The timeline will
show how scientists gradually discovered that all living
things are made of cells.
The list below shows some of the important steps that occurred.
In your group, choose one of these steps to investigate. Make
sure that you do not choose the same step as another group.
Help your group to find out more about this step. Then help
to produce an illustrated account of what happened.
This is the type of microscope
that Robert Hooke used.
Try to include an explanation of how the work of earlier
scientists helped this step to take place.
1625
Galileo Galilei builds the first microscope.
1665 Robert Hooke looks at cork (from tree bark) through a microscope, and describes
little compartments that he calls cells.
1670 Anton van Leeuwenhoek improves the microscope and is able to see living cells in
a drop of pond water.
1833
Robert Brown discovers the nucleus in plant cells
1838 Matthias Schleiden proposes that all plant tissues are made of cells. Theodor
Schwann proposes that is also true of animal cells.
1845
Carl Heinrich Braun proposes that cells are the basic unit of all life.
1855
Rudolf Virchow says that all cells only arise from other cells.
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1 Cells
Check your Progress
1.1 Different cells have different functions.
Name the cell that carries out each function.
Choose from the list.
red blood cell root hair cell palisade cell neurone ciliated cell
a
Moves mucus up through the airways.
[1]
b
Absorbs water from the soil.
[1]
c
Makes food by photosynthesis.
[1]
1.2 The diagram shows an animal cell.
A
B
C
D
a
Name the parts labelled A, B, C and D.
b
Describe two ways you can tell that this is an animal cell and not a plant cell. [2]
[4]
1.3 The diagram shows a plant cell.
A
B
C
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D
E
1 Cells
For each letter, A–E, write the name of the cell part and its function.
Choose from these lists:
[5]
Names:
mitochondrion cell membrane nucleus cell wall chloroplast
Functions:
holds the cell in shape
controls what goes in and out of the cell
where photosynthesis takes place
where energy is released from nutrients
controls the activities of the cell
1.4 The diagram shows a specialised cell from the human body.
a
What is the name of this cell?
[1]
b
What is the function of this cell?
[1]
c
Describe how the cell is adapted to carry out its function.
[1]
d
Name the system in the human body that this cell is part of.
[1]
1.5 These sentences are about the way that cells are grouped together in
complex organisms.
Copy and complete each sentence. Choose from the list.
cell tissue organ organ system
a
In a complex organism, such as a human or a plant, similar cells are grouped
.
together to form a
b
The stomach is an example of an
c
The heart and blood vessels are all part of the same
[1]
[1]
.
.
[1]
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2
Materials and
their structure
2.1 Solids, liquids and gases
In this topic you will:
•
sort the states of matter into solids, liquids and gases
•
learn about the properties of solids, liquids and gases
•
use particle theory to describe the structure of solids, liquids
and gases
•
Most of this image is obscured by
the feature boxes, Please swap
it for something else.
Tech-Set:- Please advise
use particle theory to learn about the properties of solids,
liquids and gases.
Getting started
Key words
1
Name two solids, two liquids and two gases.
2
Copy and complete the table. Use the substances you listed
in Question 1. Discuss your reasons for each decision with
your group.
compressed
flow
hypothesis
matter
particle
pour
property
states of matter
theory
vacuum
vibrate
volume
Substance
Solid, liquid or gas
Example: tap water liquid
I know this
because…
I can pour it.
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2.1 Solids, liquids and gases
An updated version of
this was received
in July
Looking at states of matter
Tech-Set:- Please
advise as this is
version we have
received
Everything you can see and feel is called matter. Scientists sort
matter into three groups or states called ‘solids’, ‘liquids’ and
‘gases’. These states of matter behave in different ways. The
ways they behave are called their properties.
Solids
Solids keep the same shape. Solids take up the same amount
of space. Solids keep the same volume. Solids cannot be
compressed (squashed) or poured.
Liquids
Liquids take the shape of the container they are in.
Liquids can be poured. Liquids cannot be compressed.
Liquids take up the same amount of space, whatever shape
their container.
An updated version of
this was received
in July (He should
be wearing safety
glasses and a lab
coat.)
The volume of a liquid does not change.
Tech-Set:- Please
advise as this is
version we have
received
Gases
Gases flow like liquids. They will fill any closed container
they are in.
Gases are very easy to compress. The volume of a gas can
change. Gases weigh very little. Generally, you cannot see
or feel gases, but you can sometimes smell them, and you can
feel air moving on your face.
100cm
50cm
100cm
50cm
0cm
0cm
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2 Materials and their structure
Questions
1
What are the three states of matter?
2
Which state of matter can be compressed (squashed) easily?
3
Which state of matter cannot be poured?
4
List the properties of solids.
5
Name a property of liquids that they do not share with solids.
6
Name a property of gases that they share with liquids.
7
Name a property of gases that they do not share with solids
or liquids.
Scientists look at what matter does
Scientists try to explain what they see. Here are some examples of how
matter behaves that scientists have tried to explain.
•
You can smell food cooking in another room.
•
Some substances get bigger when you heat them.
•
Liquids, such as water, change to a gas when you heat them.
•
Substances change from liquid to solid if you cool them.
Scientists think about why these things happen and try to come up
with ideas to explain it. They form an hypothesis, which is a suggestion
for an explanation. This hypothesis can then be tested by carrying out
more investigations.
When an hypothesis has been tested and widely accepted as valid by
other scientists, it is called a theory.
The best theory to explain how matter behaves uses the idea of
particles. Particles are tiny portions of matter. This theory says
that all matter is made up of tiny particles arranged in
different ways.
Particle theory
All matter is made up of tiny particles that are much too small to see.
The particles are arranged differently in solids, liquids and gases.
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2.1 Solids, liquids and gases
Solids
In solids the particles are arranged in a fixed
pattern. The particles are held together strongly and
are tightly packed together. This is why solids have a
fixed shape.
The particles in a solid can vibrate (make small
movements) but they stay in the same place.
In solids the particles are packed together and
can vibrate. They stay in the same place.
Liquids
In liquids the particles touch each other.
The particles are held together weakly. The particles
can move past one another but they still touch each
other. Liquids can change shape.
In liquids the particles touch each other, can move
and can change places.
Gases
In gases the particles do not touch each other.
They are a long way apart. The particles spread
out by themselves. The particles can spread out
to fill up the space they are in. Gases can change
shape.
In gases the particles are far apart and can move
about freely.
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2 Materials and their structure
Think like a scientist
Modelling the particles in solids, liquids and gases
In this task, you will describe the strengths and weaknesses of a model.
Work in a small group.
•
Arrange yourselves in a pattern, as if you are the particles in a solid.
•
Now arrange yourselves as if you are the particles in a liquid.
•
Now arrange yourselves as if you are the particles in a gas.
Questions
1
With a partner, discuss and describe the ways in which the
particles are arranged in the three states of matter.
2
Copy and complete these sentences to describe how
particles are arranged in solids, liquids and gases.
•
In solids, the particles are arranged
•
In liquids, the particles are arranged
•
In gases, the particles are arranged
Self-assessment
In what ways was your group a good model for the particle
theory? Think about how well you did for each of the solid,
liquid and gas models.
•
Were you in regular rows?
•
Were you touching the people around you?
•
Could you change your position?
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Would be nicer if the
hot air balloon
could be cut out
and overlap the
feature box.
Tech-Set:- Please
note that the low
res image has
been feathered
(not actioned by
TS) prior to cut
out being made
2.1 Solids, liquids and gases
Explaining the properties
Matter can only flow (be poured) if the particles can
move past one another.
Matter can only change volume if the particles in it
can spread out or move closer together.
Solids
The particles in a solid are very close together.
This makes it difficult for the volume of a solid
to be made smaller. Solids have a fixed shape
because attractive forces hold the particles together.
These forces stop the particles from moving around.
The particles can only vibrate. This means that a
solid cannot flow.
Solids cannot flow.
Liquids
The volume of a liquid cannot be changed. The
particles are very close together and cannot be
squashed. The particles touch each other but they
can move past each other. The attractive forces
between the particles are weak enough to allow
them to move but strong enough to hold them
together.
Liquids can flow.
Gases
Particles in a gas are a long way apart so they can
move quickly in all directions. The particles can
move easily because there are no attractive forces
between them. This means that gas has no fixed
shape or volume.
When you squash a gas, the particles move closer
together and the gas takes up less space.
No particles?
A space where there are no particles at all is called
a vacuum. A vacuum contains nothing.
Gases can flow and spread out.
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2 Materials and their structure
Think like a scientist
Particle theory
Scientists observe the world around them and think carefully about what they see.
Development of the particle theory was based on the observations that scientists made
about how solids, liquids and gases behave.
Scientists saw that most solids cannot be compressed. Can you think of any solids that
do not fit the rules of particle theory? Think about the properties of a sponge or
a marshmallow. Can a sponge be compressed?
Questions
1
Use particle theory to explain how a sponge can be a solid, but it can also
be compressed.
2
How well does particle theory explain the properties of solids, liquids and gases?
3
What are the strengths of the particle theory?
4
What are the weaknesses of the particle theory?
Activity
States of matter
On a large piece of paper, draw three large squares and label them ‘solid’, ‘liquid’ and
‘gas’, like this. Leave space around them.
Solid
Liquid
Gas
In each square, draw how the particles are arranged in that state of matter.
In the spaces around the squares, write the properties of the three states of matter.
Summary checklist
I can classify matter as a solid, liquid or gas.
I can list the properties of solids, liquids and gases.
I can describe the way in which particles are arranged in solids,
liquids and gases.
I can explain the properties of solids, liquids and gases using
particle theory.
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2.2 Changes of state
2.2 Changes of state
In this topic you will:
•
practise measuring the volume and the temperature
of a liquid
•
learn what happens when matter changes state
•
investigate the temperature increase when you heat water.
Getting started
Key words
With a partner, draw three diagrams to show the particle
structure of a solid, a liquid and a gas.
boil
boiling point
change of
state
condensation
condense
evaporation
freeze
measuring
cylinder
melt
melting point
meniscus
steam
thermometer
water vapour
Be ready to show the class when you are asked to do so.
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2 Materials and their structure
Changing state
If you leave ice in a warm place it melts and becomes liquid water.
The temperature at which a solid melts is called the melting point.
Water on the ground will gradually disappear as it changes to water
vapour, an invisible gas. This is called evaporation. The warmer the
water, the more quickly it evaporates.
If you heat water until its temperature reaches 100 °C, it will boil.
All of the water rapidly changes to steam. Steam is water heated to
the point that it turns into a gas. 100 °C is the boiling point of water.
If the water vapour or steam touches something cold, it condenses and
changes back to liquid water. This is called condensation.
If you put liquid water in the freezer, it freezes and becomes ice.
These changes are known as changes of state.
steam
water
ice
boiling
melting
condensing
freezing
Activity 2.2.1
Which change of state?
Work in pairs.
Cut out nine rectangles from a piece of A4 card. Write these words onto the cards: melt,
freeze, condense, boil, liquid, gas, solid, from, to.
One of you should have the change of state cards (melt, freeze, condense, boil). The
other should have the remaining cards (liquid, gas, solid, from, to).
Hold up a change of state card. Your partner should then select the correct cards to
show which state is changing to which other state. For example: ‘freeze’ would be from
‘liquid to solid’.
Swap the sets of cards so that you take turns.
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2.2 Changes of state
Measuring
Measuring volume
When you measure the volume of a liquid you use a measuring cylinder.
The liquid forms a curve at the top. This is called the meniscus.
You measure the volume from the bottom of the meniscus. To do this,
you must make sure that your eye is level with the meniscus.
meniscus
°C
Measuring the volume of water in a measuring cylinder.
Measuring temperature
When you measure the temperature you use a thermometer. The liquid
inside the thermometer expands as it gets hotter, so it rises up inside the
thermometer. You read the temperature from the scale. Make sure that
your eye is level with the top of the liquid in the thermometer.
A thermometer
Questions
1
Look at the diagram. What is the volume of water in each
measuring cylinder?
A
C
B
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2 Materials and their structure
2
What are the temperatures shown on the thermometers?
A
B
C
Think like a scientist
Measuring the temperature when you heat water
In this task you will take accurate measurements.
You will need:
beaker, Bunsen burner, clamp stand, gauze,
measuring cylinder, thermometer, tripod
Safety
Wear safety spectacles. Take care when handling hot water.
Work in groups of two or three. Before you start the activity, discuss in your group what
other safety measures you will take. Check these with your teacher.
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2.2 Changes of state
Updated artwork was supplied in July with the boy
wearing a lab coat.
However, there are other changes that need to be
made. See below.
Continued
safety spectacles
Tech-Set:- Equipment labeling and corrections have
been made. Changes to Arun ie wearing a lab
coat not actioned as we have not recieved this
version of him.
clamp stand with boss
beaker
gauze
bunsen burner
stopwatch
measuring cylinder
tripod
heat-proof mat
1
Accurately measure of water into a beaker.
2
Place a thermometer with its bulb in the water. Use a clamp stand, as shown in
the illustration. This is so that you measure the temperature of the water, not the
temperature of the bottom of the beaker.
3
Measure the temperature.
4
Record this in a table. (Copy and extend the one below.)
Time in minutes
SEE QUERY LOG: Q1
Quantity missing.
Tech-Set:- no
quantity amount
mentioned in
query log OR on
marked pdf!
Temperature in °C
0
1
2
3
4
33
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2 Materials and their structure
Continued
5
Heat the water.
6
Use the thermometer to measure the temperature every minute.
7
Repeat until the water is boiling vigorously.
Questions
1
Plot your temperature measurements on a graph. Put the time along the horizontal
axis and the temperature on the vertical axis.
2
Describe your graph. You could complete these sentences.
•
When we heated the water, the temperature
•
The longer we heated the water, the
•
The increase in temperature was
the temperature
You could mention how quickly the temperature increased and if the temperature
increased by the same amount each minute.
3
What happened to the temperature of the water when it was boiling?
4
Why do you think this happened?
5
The thermometer is held in the water so that it does not rest on the bottom of the
beaker. Why?
•
Describe any problems you had with this investigation.
How did you solve them?
•
Think about how you carried out this investigation.
What did you do to keep safe? Could you have made
the investigation any safer?
Summary checklist
I can name the three states of matter.
I can use the correct terms to say how water changes from solid to
liquid to gas.
I can use a thermometer and a measuring cylinder accurately.
I can carry out an investigation safely.
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2.3 Explaining changes of state
2.3 Explaining changes
of state
In this topic you will:
•
use the particle theory to explain what happens when matter
changes between states
•
use a model to illustrate the particle theory.
Getting started
Key words
1
attractive force
expand
heat energy
transferred
2
For each process, write down the changes of state. The first
one has been started for you.
•
Melting: solid to
•
Condensing:
•
Freezing:
For each statement, decide if it applies to a solid, a liquid or
a gas. Some may apply to more than one state of matter.
particles in
regular rows
can be
poured
can be
compressed
particles
spread out
has a fixed
volume
can change
its shape
cannot be
compressed
has a
fixed shape
Check with a partner. Are you correct?
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2 Materials and their structure
Changes of state
Heating solids
When solids are heated they expand (get bigger).
The particles in solids are arranged in a fixed pattern.
The particles are held together strongly and are tightly packed.
The particles in the solid vibrate. When the solid is heated,
heat energy is transferred to the particles in the solid.
The more energy the particles have, the more they vibrate.
As the particles vibrate more, they take up more space.
The particles are still held in position by the attractive forces
between them.
Melting solids
When solids are heated more strongly, they melt. They become
liquid. (Heating more strongly means that even more heat
energy is transferred to the particles.)
When a solid is heated, the particles
vibrate more and take up more space.
The particles in a solid vibrate more and more as heat energy is
transferred to them. The particles vibrate so much that the attractive
forces between them are not strong enough to hold them in a fixed
pattern. The particles can slide past one
another – they can now move, not just vibrate.
The forces are still strong enough for the particles to stay in
touch with one another. The more the liquid is heated, the more
energy is transferred to the particles and the more the particles
vibrate and move.
The particles vibrate so much that some escape the strong forces and can move around
as a liquid.
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2.3 Explaining changes of state
Boiling liquids
When liquids are heated, they evaporate and boil.
The particles in liquids touch each other.
The particles are held together weakly.
The particles move more as heat energy is transferred
to them. Some particles have enough energy to break
the weak attractive forces holding them together.
These particles can move freely and escape as
gas particles.
The particles move so quickly that some escape as
a gas.
Cooling gases
cold surface
The particles in a gas are free to move anywhere
and spread out. There are no forces holding them.
When a gas gets cooler it condenses to form a liquid.
When gas particles reach a cold surface, some of
the heat energy from the particles transfers to the
surface. The particles move less and get closer
together. They form a liquid.
Freezing liquids
When a liquid freezes it becomes a solid.
The particles in a liquid can move and flow past
each other. As heat energy is transferred from the
particles to the surroundings, the particles move
more slowly and the liquid gets cooler.
The cooler the liquid, the less energy the particles
have. The less energy the particles have, the less
able they are to move or slide past one another.
Eventually, the particles have so little energy they
cannot move and flow anymore – they can only
vibrate. They become arranged in a fixed pattern
to form a solid.
When the particles hit a cold surface, their movement
slows down.
Particles in a liquid (left). Particles in a solid (right).
Questions
1
Explain why a solid expands when it is heated.
2
Use particle theory to explain why solids and liquids cannot be
compressed (squashed into a smaller volume).
3
Use particle theory to explain why liquids and gases can flow.
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2 Materials and their structure
4
Use particle theory to explain how a liquid changes to a gas.
5
Use particle theory to explain how a liquid changes to become
a solid.
6
Use particle theory to explain what happens when steam in the
bathroom hits a cold surface, such as a mirror.
7
Copy this flow chart. The arrows represent the processes involved
when matter changes state. Add the name for each process, A–D.
liquid
solid
A ……….…....
gas
B ……….…....
liquid
solid
C ……….…....
gas
D ……….…....
Think like a scientist
Modelling changes of state
In this task, your class will model the changes of state by arranging yourselves as
particles. You will need a lot of space.
Solid to liquid
•
As a class, arrange yourselves as if you are the particles in a solid.
•
Imagine the particles are being heated. Move as if you are being heated gently.
Move as the particle theory suggests you should.
•
Imagine the particles are now being heated strongly, so that the solid melts and
becomes a liquid. Remember to behave as the particle theory suggests you should.
Question
1
Describe how you had to act to illustrate the behaviour of particles as a solid melts.
Think about how you behaved. Was the model a good or a bad model for particle
theory? Explain.
Liquid to gas
•
As a class, arrange yourselves as if you are the particles in a liquid.
•
Imagine the particles are being heated. Move as if you are being heated gently.
•
Imagine the particles are now being heated strongly so that the liquid boils.
Remember to behave as the particle theory suggests you should.
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2.3 Explaining changes of state
Continued
Question
2
Describe how you had to act to illustrate the behaviour of particles as a liquid
evaporates and then boils. Think about how you behaved. Was the model a good
or a bad model for particle theory? Explain.
Gas to liquid
•
As a class, arrange yourselves as if you are the particles in a gas.
•
Imagine part of the room is a cold surface. As you move near to the surface you must
behave as particle theory suggests. You should start to condense to form a liquid.
Question
3
Describe the way you had to behave to illustrate the behaviour of particles as a gas
condenses. Think about how you behaved. Was the model a good or a bad model
for particle theory? Explain.
Liquid to solid
•
As a class, arrange yourselves as the particles in a liquid. Make sure you move as
particle theory suggests.
•
Now imagine the liquid has been placed in a freezer. Behave as particle theory
suggests, as you become a solid.
Question
4
•
Describe the way you had to behave to illustrate the behaviour of particles as a liquid
freezes to form a solid. Think about how you behaved. Was the model a good or a
bad model for particle theory? Explain.
How did you learn and remember the structure of solids,
liquids and gases as states of matter?
Summary checklist
I can describe how particles behave, depending on how much
energy they have.
I can explain that energy can be transferred to or from particles.
I can describe the effects of the energy on the forces holding the
particles together.
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2 Materials and their structure
2.4 The water cycle
In this topic you will:
•
learn about the water cycle
•
use scientific words to describe stages of the water cycle.
Getting started
Key words
Spend one minute thinking about where rain comes from.
Then spend two minutes discussing your ideas with a partner.
atmosphere
groundwater
open water
precipitation
surface run-off
transpiration
water cycle
water vapour
Now write down your ideas and show them to your teacher.
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2.4 The water cycle
The water cycle
Water is vital for all living things. Our bodies are made up of at least
60% water.
Water on Earth is constantly moving. The water moves between rivers,
lakes, oceans, the atmosphere and the land. It is recycled over and over
again in a continuous system called the water cycle. You are still using
the same water that the ancient Greeks and the Romans used. The Earth
has been recycling water for more than four billion years.
condensation
precipitation
evapotranspiration
evaporation
oceans
streamflow
water
groundwater flow
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2 Materials and their structure
What happens during the water cycle?
Water moves into the atmosphere
Energy from the Sun heats the Earth and the temperature
of the water in the rivers, lakes and oceans increases. When
this happens, some of the liquid water forms water vapour.
This is called evaporation. This happens because some of
the particles in the liquid water gain enough energy to break
free from the forces holding them together and they change
to a gas. Water can also evaporate into the atmosphere from
plants; this is called transpiration.
Water in the atmosphere cools down
As the water vapour goes up into the atmosphere, it cools
and changes back into little droplets of water in the air,
forming clouds. This process is called condensation. It
happens because the particles in the water vapour lose
energy and cannot move so quickly. Air currents high in the
atmosphere move the clouds around the world.
Water falls from clouds
When a lot of water has condensed, the water droplets in
the clouds become too heavy for the air to hold them. The
droplets fall back to Earth as rain. If the drops become
colder they may form snow, hail or sleet. This process is
called precipitation.
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2.4 The water cycle
Water falls on the Earth
The precipitation that falls then collects
in rivers and open water such as large
lakes and the oceans.
How it is collected depends on where it
lands. Some precipitation will fall directly
onto the rivers, lakes and oceans and will
evaporate, then the cycle starts again.
If the precipitation falls on plants it may
evaporate from the leaves back to the
atmosphere or trickle down to the ground.
The plant roots in the ground may then
take up some of this water.
Water in the ground
Some of the water from precipitation will soak into the soil and rocks
as groundwater. Some of this water will stay in the shallow soil layer and
will move towards streams and rivers. When groundwater soaks deeper
into the soil, it refills underground stores.
In cold climates the precipitation may build up on land as snow, ice or
glaciers. If the temperatures rise, this solid snow and ice will melt into
liquid water, which soaks into the ground or flows into rivers or the
ocean.
Some of the precipitation will soak into the soil and move through
the ground until it reaches the rivers or the open water, large lakes
and the oceans.
Water that reaches the surface of the land may flow directly across the
ground into the rivers, lakes and oceans. This water is called surface
run-off. When there is a lot of surface run-off, soil can be carried off
the land and into the rivers. This can cause them to become silted up
and blocked.
Activity 2.4.1
Water cycle poster
Make a poster to show the water cycle. Remember to use the
scientific terms. You should make your poster as clear and
colourful as you can.
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2 Materials and their structure
Continued
Peer assessment
Swap your poster with someone else in your class. What do you
like about their poster? Think of at least two things. How could
they improve their poster?
Questions
1
What are the different types of precipitation?
2
How does rain form?
3
Use particle theory to explain how a pool of water on the
road disappears.
4
Where does your drinking water come from?
5
What methods have people used to ensure they always have
a supply of water? You may need to do some research.
6
What do we use water for in our bodies?
7
What other things do we use water for?
8
Think about all the water you used today. Try to work out how
much water you use in one day.
Summary checklist
I can use scientific vocabulary to describe the water cycle.
I can use particle theory to explain what happens in each part of
the water cycle.
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2.5 Atoms, elements and the Periodic Table
2.5 Atoms, elements and
the Periodic Table
In this topic you will:
•
learn what an atom and an element are
•
find out about different atoms and elements
•
learn about the Periodic Table
•
use symbols to represent the names of elements.
Getting started
Key words
1
Draw a diagram to show how particles are arranged in a solid
and explain how the arrangement of particles changes when
the solid melts.
2
What do you need to do to a solid to make it melt?
atom
element
group
metals
nanotube
non-metal
period
symbol
The Periodic
Table
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2 Materials and their structure
What are atoms?
Over 2000 years ago, a Greek philosopher called Democritus
suggested that everything was made up of tiny pieces. Democritus
suggested that, if you could keep on cutting up a substance into
smaller and smaller pieces, you would end up with a very small
piece that could not be cut up any more.
Democritus called his tiny pieces of matter atoms.
Atom means ‘cannot be divided’.
We now know that atoms really do exist. Today we can even
see some of the large kinds of atom, using special microscopes
called scanning tunnelling microscopes. The photograph shows
the atoms in some carbon nanotubes.
(Nano means ‘very, very small’.)
Nanotubes
Different types of atom
There are many different types of atom. Scientists have discovered
94 different types of atom that occur naturally in the universe.
Another 24 kinds of atom have been made in laboratories.
Some substances are made up of just a single kind of atom.
A substance made of just one kind of atom is called an element.
For example, carbon is made only of carbon atoms. Gold is made
only of gold atoms. Silver is made only of silver atoms.
Carbon, gold and silver are examples of elements.
Each type of atom has different properties. This is why different
elements have different properties.
These rings are made from pure silver.
If you could see some of the atoms in the silver ring, they
would look something like this.
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2.5 Atoms, elements and the Periodic Table
Questions
1
What are atoms?
2
If there are 94 different kinds of naturally occurring atom,
how many different naturally occurring elements are there?
Atoms joining together
In six of the elements, such as neon (which is a gas), atoms move around
freely, not attached to one another. But in most elements, such as gold
and other metals, atoms are packed closely together.
In a small number of elements, such as oxygen and sulfur, atoms join
together to form small particles. An oxygen particle is made from two
oxygen atoms. A sulfur particle is made from eight sulfur atoms.
Atoms of neon
Atoms of gold
Particles of oxygen
Particle of sulfur
Arranging the elements
Scientists have developed a very useful way of arranging the elements.
This is called the Periodic Table.
The full Periodic Table containing all of the 118 known elements is
very large and complex. (There may be one on the wall of your science
laboratory.) You are just going to look at the first 20 elements.
SEE QUERY LOG
118 = 94 natural + 24 man-made.
Consider adding a brief explanation
that 118 = 94 natural + 24 man-made
to the text.
Tech-Set:- Query log confirmation
column has no information in. And
nothing is marked on the PDF as to
what needs to be entered.
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2 Materials and their structure
metals
non-metals
H
He
hydrogen
helium
Li
Be
B
C
N
O
F
Ne
lithium
beryllium
boron
carbon
nitrogen
oxygen
fluorine
neon
Na
Mg
Al
Si
P
S
Cl
Ar
sodium
magnesium
aluminium
silicon
phosphorus
sulfur
chlorine
argon
K
Ca
potassium
calcium
Groups and periods
The Periodic Table is organised into rows and columns. The rows are
called periods. The columns are called groups.
The atoms are organised so that, as you read across each row (period)
from left to right, the atoms increase in mass. Hydrogen atoms have the
smallest mass, then helium atoms, then lithium atoms, and so on.
Chemical symbols
Each of the elements has been given a symbol.
This is a useful shorthand way of referring to them.
Sometimes the symbol is the first
letter of the English name of the
element. For example, the symbol
for oxygen is O.
Aluminium, Al
Sometimes the symbol is the first
letter of the English name plus
another letter from its name.
For example, the symbol for helium
is He.
Sometimes the symbol is taken from
another language. For example, the
symbol for sodium is Na, from the
old Latin name ‘natrium’.
Zinc, Zn
Bromine, Br
Lead, Pb
Copper, Cu
The first letter of the symbol is
always upper case and the second
letter, if there is one, is always lower case.
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Iron, Fe
2.5 Atoms, elements and the Periodic Table
Questions
3
What are the names of the elements with the symbols Mg, Be,
Li and N?
4
Find the symbols for the elements aluminium, boron, fluorine
and potassium.
5
Which element has atoms with the smallest mass?
6
Which of the elements in the first 20 elements of the Periodic Table
has atoms with the greatest mass?
7
Give the names (not symbols) of two elements in the same period
as magnesium.
8
Give the symbols (not names) of two elements in the same group
as helium.
Metals and non-metals
The Periodic Table is organised so that elements with similar properties
are close together.
In the diagram of the Periodic Table, all the elements that are metals are
in yellow boxes. All the elements that are non-metals are in blue boxes.
Activity
Learning the symbols for the elements
Here is a list of twenty elements and their symbols. Your task is to make up a game to help
you learn them. You could make one set of cards with the names on them and another set
with the symbols on them. Think how you could use these to make a game.
Your game could be for one or two people, you decide.
Element
Symbol
Element
Symbol
Hydrogen
H
Sodium
Na
Helium
He
Magnesium
Mg
Lithium
Li
Aluminium
Al
Beryllium
Be
Silicon
Si
Boron
B
Phosphorus
P
Carbon
C
Sulfur
S
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2 Materials and their structure
Continued
Element
Symbol
Element
Symbol
Nitrogen
N
Chlorine
Cl
Oxygen
O
Argon
Ar
Fluorine
F
Potassium
K
Neon
Ne
Calcium
Ca
How do you learn facts? Does a game help? Which is the most
effective way of learning for you?
Summary checklist
I can explain what an atom and an element are.
I can identify twenty elements and their symbols.
I can use symbols to represent elements.
I can describe the Periodic Table.
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2.6 Compounds and formulae
2.6 Compounds and formulae
In this topic you will:
•
learn about the differences between elements
and compounds
•
learn how to name compounds
•
use symbols to represent compounds.
Getting started
Key words
You have three minutes. Test your partner on the symbols for
the elements.
bonding
compound
formula
sodium chloride
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2 Materials and their structure
What is a compound?
You have looked at elements in the Periodic Table. An element is made
up of only one type of atom. Many substances are made up of more
than one type of atom. If the different types of atom are joined tightly
together, then the substance is a compound.
The chemical term for two atoms joining tightly together is bonding.
In a compound, two or more different kinds of atom are bonded.
For example, when sodium atoms bond with chlorine atoms, they
form the compound sodium chloride.
Properties of elements and
compounds
A compound is very different from the elements from which it is made.
When two different elements are bonded, they completely lose the
properties of the individual elements. The compound has totally
new properties.
The first two photographs show the two elements sodium and chlorine.
The third photograph shows the compound that is made when sodium
and chlorine atoms bond together. This compound – sodium chloride –
is not at all like either sodium or chlorine.
+
Sodium, an
element
Chlorine, an
element
Sodium chloride, a
compound
You may have eaten some sodium chloride today. Sodium chloride
is common salt. You would not want to eat any sodium or
chlorine, though.
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2.6 Compounds and formulae
Questions
1
Describe two ways in which sodium chloride is different
from sodium.
2
Describe two ways in which sodium chloride is different
from chlorine.
Naming compounds
Each compound has a chemical name. The chemical name usually tells
you the elements that the compound is made from.
There are important rules to remember when naming compounds.
•
If the compound contains a metal, then the name of the metal
comes first in the name of the compound.
•
If the compound contains a non-metal, the name of the non-metal
is usually changed. For example, the compound made from sodium
(a metal) and chlorine (a non-metal) is not sodium chlorine, but
sodium chloride.
•
When two elements form a compound the name often ends in ‘ide’.
Questions
3
Which two elements are combined in sodium chloride?
4
Which two elements are combined in hydrogen sulfide?
5
Which two elements are combined in magnesium oxide?
6
A student wrote this name for a compound
made of calcium and sulfur:
sulfur calcium
What is wrong with this name?
Write the correct name for the compound.
These are crystals of copper sulfate. Copper sulfate is a
compound made up of copper, sulfur and oxygen.
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2 Materials and their structure
Questions
Some compounds contain two different elements, plus a third element –
oxygen. These compounds often have names ending with ‘ate’.
For example, a compound of calcium, carbon and oxygen is called
calcium carbonate.
7
Which three elements are combined in calcium nitrate?
8
Which three elements are combined in magnesium carbonate?
9
Which three elements are combined in lithium sulfate?
Sometimes, the name of a compound tells you how many of each kind
of atom are bonded together.
O
C
O
C
A particle of carbon dioxide
O
A particle of carbon monoxide
Carbon dioxide particles are made up of one carbon atom joined to two
oxygen atoms. ‘Di’ means two.
Carbon monoxide particles are made up of one carbon atom joined to
one oxygen atom. ‘Mon’ or ‘mono’ means one.
Particle diagrams
Particle diagrams, like those for carbon dioxide and carbon monoxide,
show which atoms of which elements make up the particle.
It is easy to decide if a substance is a compound by looking at the
particle diagram. If there are different kinds of atom bonded together,
then it is a compound.
H
H
C
O
C
O
A molecule of carbon
dioxide, CO2
H
O
H
A molecule of water,
H2O
O
O
A molecule of
oxygen, O2
Carbon dioxide, water and methane are all compounds because their
particles are made up of different kinds of atom. Oxygen is an element
because the atoms in the particle are both oxygen atoms.
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H
H
A molecule of
methane, CH4
2.6 Compounds and formulae
Using formulae
Every compound has a chemical name. For example, the compound of
sodium and chlorine is sodium chloride. Some compounds also have an
everyday name. For example, sodium chloride is also known as common salt.
Every compound also has a formula. The formula contains the symbols
of the elements that are bonded together in the compound.
The table shows the chemical names and formulae of six compounds.
Chemical name
Formula
What the compound
contains
calcium oxide
CaO
one calcium atom
bonded with one
oxygen atom
carbon dioxide
CO2
one carbon atom
bonded with two
oxygen atoms
carbon monoxide
CO
one carbon atom
bonded with one
oxygen atom
hydrogen sulfide
H2S
two hydrogen atoms
bonded with one
sulfur atom
calcium carbonate
CaCO3
one calcium atom,
one carbon atom
and three oxygen
atoms bonded
together
sodium hydroxide
NaOH
one atom of sodium,
one atom of oxygen
and one atom of
hydrogen bonded
together
Be very careful reading the symbols of the elements. You do not want to
confuse the symbol for carbon, C, with the symbol for calcium, Ca.
The little number written below and to the right of some symbols tells
you how many atoms of each element are found in the particle of the
compound. If there is no number, it means there is just one atom of
that element.
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2 Materials and their structure
Questions
10 Which of these substances are elements, and which are compounds?
Explain your answer.
K
O2
NaCl
Al
Ca
CaCl2
H2
11 The formula for sulfur dioxide is SO2.
a
How many different elements are combined in sulfur dioxide?
b
How many atoms of oxygen are combined with each atom
of sulfur?
12 The formula for water is H2O.
a
Which two elements are combined in water?
b
What does the formula tell you about the numbers of each
kind of atom that are combined together?
13 The compound with the formula CO is called carbon monoxide.
Suggest why it is not simply called ’carbon oxide’.
14 Suggest the names of the compounds with these formulae:
a
MgO
b
NaCl
c
CaCl2.
15 The formula for sodium hydroxide is NaOH; the formula for
potassium hydroxide is KOH.
Which two elements are do you think contained in all hydroxides?
16 What is the name of the compound with the formula LiOH?
17 How many different elements are combined together in LiOH?
Activity 2.6.1
Making models of particles
You are going to make models of at least five of the compounds
mentioned in this topic.
You will need:
•
coloured card or paper, scissors and glue
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2.6 Compounds and formulae
Continued
1
Cut out circles of different colours to represent the different
atoms of the elements.
2
Write the symbol for that element on the atom.
3
Arrange them to form the formula of one of the compounds
mentioned in this topic.
4
Stick them on to a poster and write the name of the
compound and its formula underneath.
5
Display them in your classroom.
Summary checklist
I can explain the difference between elements and compounds.
I can name compounds.
I can use symbols to represent elements and compounds.
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2 Materials and their structure
2.7 Compounds and mixtures
In this topic you will:
•
make a compound and a mixture
•
learn about the difference between a compound and a
mixture
•
give examples of mixtures.
Getting started
Key words
•
composition
evaporating basin
filings
mineral
mixture
natural emissions
pipe-clay triangle
pure
Which of these are elements and which are compounds?
nitrogen
O2
carbon dioxide calcium chloride
CaO
CH4
H2O
sodium
K
•
What is the difference between an element and a
compound?
•
Discuss with a partner and be prepared to share with the
class.
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2.7 Compounds and mixtures
Compounds and mixtures
When atoms of elements are bonded tightly
to form a compound, the properties of the
compound are completely different from the
properties of the elements that it is made from.
For example, iron is a metal. It is hard, grey,
strong, conducts heat and electricity and
is magnetic.
Sulfur is a non-metal. It is yellow, brittle,
does not conduct heat or electricity and is
not magnetic.
When these two elements are heated, they
combine together to form the compound iron
sulfide. Iron sulfide is not magnetic and does
not conduct heat or electricity.
This miner is carrying baskets of sulfur from the crater
of a volcano in Indonesia.
This blacksmith is using iron to make a bracelet.
sulfur atom
iron atom
When iron and sulfur are heated together, iron atoms
and sulfur atoms bond together to form the compound
iron sulfide.
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2 Materials and their structure
Think like a scientist
Using iron and sulfur
You are going to use iron and sulfur to make a mixture and a compound. This will help
you understand the differences between a mixture and a compound.
You will need:
safety glasses, beaker, stirrer, boiling tube, test tube holder,
Bunsen burner, powdered sulfur, iron filings, mineral wool
Safety
Do not touch your face or eyes when handling the iron filings. The pieces have sharp
edges and can damage your skin and eyes. Wear safety glasses. Carry this activity out
in a well-ventilated room.
Mixing iron and sulfur
1
Place some iron filings in a beaker.
2
Add some yellow powdered sulfur.
3
Stir the mixture so that the two
elements are spread out evenly.
You now have a mixture of iron and
sulfur. The iron and sulfur both still
have their properties. They have not
changed chemically in any way. The
different properties of the two
elements can be used to separate
them from the mixture.
4
Use a magnet to remove the iron filings.
Making a compound from iron and sulfur
1
Make a mixture of iron and sulfur, just as you did in steps 1–3.
2
Heat some of the iron and sulfur mixture in a boiling tube.
3
Stop heating as soon as the mixture starts to glow. The iron and sulfur will combine
together and form iron sulfide.
4
Leave the tube to cool.
5
Use a magnet to try to separate the iron. You can try through the wall of the tube.
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2.7 Compounds and mixtures
Continued
Questions
1
2
Describe the appearance of:
a
a mixture of iron and sulfur
b
the iron sulfide.
Can you remove the iron from the iron sulfide by using a magnet?
Explain your answer.
Air is a mixture
When you mix iron and sulfur together, you make a mixture
of two elements.
78% nitrogen
In science, the word pure is used to describe something that
only contains a single substance. Pure water contains only
water, with no other substances mixed with it.
A mixture is not pure. It is made up of different
kinds of particle that are mixed together. The mixture
may be of elements, compounds or both. There are
solids, liquids and gases that are mixtures.
For example, air is a mixture of several different elements
and compounds. Air contains nitrogen, oxygen, carbon
dioxide, water vapour and small quantities of some
other gases.
The composition of air varies because the amount of water
vapour changes all the time, depending on the weather.
1% carbon dioxide,
argon, water vapour
and other gases
21% oxygen
A pie chart showing the composition of air.
The amount of carbon dioxide and other gases also change. This can be
a result of natural emissions, such as when animals and plants produce
carbon dioxide when they respire. Plants also use carbon dioxide when
they make food, so this removes carbon dioxide from the air. The
changes in the composition of air can also be as a result of human
activity increasing the amount of carbon dioxide that is given out as a
result of burning fossil fuels. Other forms of pollution also change the
composition of the air.
The composition of air has changed over millions of years;
at one time there was much less oxygen in the atmosphere.
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2 Materials and their structure
carbon dioxide
nitrogen
oxygen
water
Air is a mixture of several elements and compounds.
Questions
The diagram shows some particles in air. The red circles represent oxygen
atoms. The black circles represent carbon atoms. The blue circles represent
nitrogen atoms. The white circles represent hydrogen atoms.
1
Which is the most common element in air?
2
How many different kinds of substance are shown in the diagram?
3
Which is the least common compound in this sample of air?
Mineral water is a mixture
The label on a bottle of mineral water lists many minerals.
There is more than just water in the bottle. The bottle contains
a mixture of water and other substances.
The minerals are dissolved in the water. The mineral water is a
solution. A litre of water may have about of minerals dissolved
in it.
Question
4
Look at the picture of a mineral water label.
List the three most abundant minerals in this bottle of
mineral water.
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TYPICAL ANALYSIS mg/l
CALCIUM
MAGNESIUM
POTASSIUM
SODIUM
BICARBONATE
CHLORIDE
SULPHATE
NITRATE
IRON
ALUMINIUM
DRY RESIDUE AT 180°C
pH AT SOURCE
55
19
1
24
248
37
13
< 0.1
0
0
280
7.4
The label shows the minerals found in
mineral water.
2.7 Compounds and mixtures
Think like a scientist
safety spectacles
Is water really a mixture?
You are going to investigate if drinking
water contains anything other
than water.
tongs
water
She should be wearing a lab
coat. Updated artwork has
been supplied.
Tech-Set:- this is the only
illustration we have recieved
evaporating basin
You will need:
pipe clay-triangle
The apparatus shown in the diagram.
tripod
Safety
Wear safety glasses. Take care during
step 2 as the solution may start to spit.
Do not touch the evaporating basin
with your hands – use tongs.
bunsen burner
Read the health and safety notes before you start.
1
Put some water in the evaporating basin and heat it until it boils.
2
Once the water starts to boil, turn the heat down and continue to heat it gently.
3
When you have evaporated off some of the water (or the solution has started to spit)
remove it from the heat.
4
Leave the evaporating basin to cool. The water may take a day or two to evaporate
completely. It will depend on the temperature.
Questions
1
Use ideas about particles to explain why the water evaporated.
2
What was left in the evaporating basin?
3
Where has this substance come from?
4
Was the water you used pure water, or was it a mixture of water and other substances?
Explain your answer.
5
Why did you need to wear safety glasses?
Summary checklist
I can distinguish between a compound and a mixture.
I can explain the difference between a compound and a mixture.
I can give examples of mixtures.
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2 Materials and their structure
Project: What’s in the parcel?
Imagine you are given a parcel. You’ve been told
you cannot open it for a few days. But you’re
desperate to know what’s inside!
What would you do?
•
How could you get some information about
what is inside?
•
What sort of things could you find out?
•
What sort of things could not be found out
without looking inside?
Each group will be given a parcel with a number
on it.
1
Your group has a few minutes to find out as
much as they can about what is in the parcel
but you must not open the parcel.
2
Discuss ideas in your group and try to give
reasons for your ideas.
3
Write down your ideas on a piece of paper or a
sticky note.
4
Swap parcels with another group. Repeat steps
1 and 2. Write your ideas on a new piece of
paper or sticky note.
5
Repeat until you have tried to discover what is inside all the parcels.
When all the groups have examined all the parcels, work together as a class to create a
poster about how you carried out the investigation.
Each group will share their ideas, with reasons on each parcel, with the whole class.
By discussing this with all the other groups the class can work together to reach some
conclusions for each parcel.
This is how scientists work. They cannot always see or touch what they are investigating.
Scientists have to use the information that is available to come up with ideas.
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2 Materials and their structure
Check your Progress
2.1 Which state of matter has the strongest forces between its particles?
[1]
2.2 Name the state of matter that fits each description.
a
Particles do not touch one another.
[1]
b
Particles are close together in a regular pattern.
[1]
c
Particles are closely packed but not in a regular pattern.
[1]
2.3 Water in a puddle on a pathway disappears on a warm day. Explain what
happens to the water particles.
[2]
2.4 a
b
Which are the two correct statements about liquids?
i
Liquids can flow and be poured into a container.
ii
The particles in liquids are far apart.
iii
The particles in liquids are arranged randomly.
iv
The particles in a liquid can only vibrate.
v
Liquids only form at temperatures above 100 °C.
[2]
A liquid changes to a solid when it freezes.
Describe what happens to the particles during this process.
[2]
2.5 Which of these terms matches the two facts?
precipitation evaporation condensation groundwater
a
This falls from clouds.
Rain, snow and hail are forms of this.
b
This is what happens when water vapour cools down.
This is a change from water vapour to a liquid.
c
[1]
[1]
When this happens, liquid water changes to water vapour.
Water from rivers and the ocean is taken up into the atmosphere.
[1]
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2 Materials and their structure
2.6 Zara heated a liquid and recorded its temperature every minute.
Here are her results.
a
Time in minutes
Temperature in °C
0
20
1
25
2
19
3
39
4
47
5
56
6
58
7
59
8
58
Copy the axes and labels below, onto graph paper.
60
50
Temperature in °C 40
30
20
0
1
2
5
4
3
Time in minutes
Plot Zara’s results on the grid.
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6
7
8
[4]
2 Materials and their structure
b
Draw a line of best fit through the points you have plotted.
[1]
c
Which reading does not fit the pattern?
[1]
d
Suggest a reason for this.
[1]
e
What happens to the temperature between 5 and 8 minutes?
[1]
f
Explain why this happens.
[1]
2.7 The diagrams in the boxes show different arrangements of particles.
A
B
C
C
D
SEE QUERY LOG
Explain that each colour represents a
different atom; otherwise A and B
could be the same, and so could C and
D.
In 2.7, consider adding an explanation
that each colour represents a different
atom.
Tech-Set:- no comments in query log
for additional text to be inserted.
Marked PDF doesn't have this
information either!
D
Give the letter of the diagram that represents:
a
particles of a compound
[1]
b
particles of an element
[1]
c
atoms of a mixture
[1]
d
atoms of an element.
[1]
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2 Materials and their structure
2.8 a
b
Give the symbol for each element.
i
magnesium
[1]
ii
oxygen
[1]
iii
hydrogen
[1]
iv
calcium
[1]
v
boron
[1]
Name the element with the given symbol.
i
C
[1]
ii
Na
[1]
iii
K
[1]
iv
Cl
[1]
v
Si
[1]
c
Explain why scientists use symbols for the elements.
[1]
d
Explain why some symbols, such as Cl and Si, have two letters.
[1]
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3
Forces and energy
3.1 Gravity, weight and mass
In this topic you will:
•
understand that the force of gravity acts between objects
•
learn about what affects the strength of the force of gravity
on an object
•
practise using the correct terms ‘weight’ and ‘mass’.
Getting started
Key words
Work individually to answer these questions.
accurate
acts towards the
centre
contact force
Earth
force of gravity
formula triangle
gravity
kilograms
mass
newtons
quantity
weight
1
Describe how gravity affects an object such as
a textbook.
2
Copy and complete this sentence by choosing
the correct word from the list.
length
mass
volume
weight
The newton, N, is a unit of …………………
3
Copy and complete this sentence.
The kilogram, kg, is a unit of …………………
Will need a different
background image as
the KW box will need
to move to where the
surfer is.
Tech-Set: Please advise
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3 Forces and energy
Gravity
When you drop an object, it falls to the ground.
What pulls the object down?
The Earth you live on is a large object with a mass of about .
Objects with large mass, such as the Earth, cause strong forces of
gravity.
All objects, even pens and pencils, cause forces of
gravity. Objects with small mass, such as pens and
pencils, cause very weak forces of gravity. That means
we do not notice other objects being attracted to
them.
The force of gravity caused by an object acts towards
the centre of the object.
You can imagine the Earth as a giant ball in space.
The force of gravity at positions around the Earth acts
towards the centre. That means when you drop an
object, the object falls in a line that points towards the
centre of the Earth.
The strength of gravity decreases as you go further
from a large object such as Earth. For example, if you
travelled away from Earth in a spacecraft, the force
of gravity from the Earth acting on you would get
smaller.
The force of gravity caused by the Earth acts toward
the centre of the Earth.
Questions
1
Draw a circle to make a diagram of the Earth.
A
Put arrows around your diagram to show the
direction of the force of gravity.
2
3
Use your diagram from question 1 to explain why
people who go to the South Pole do not fall off
the Earth. Discuss your answer with a partner.
D
The diagram shows the Earth. It is not to scale.
B
A ball is dropped from four different places, A, B,
C and D.
Draw arrows to show the direction in which each
ball will fall. The first one has been done for you.
Query log: For Q3, learners need to be told to
make a new diagram to draw the arrows onto
because the arrows will already be on their
drawing for Q1.
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Tech-Set: NO replacement text in query log or
on marked PDF please advise
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C
3.1 Gravity, weight and mass
4
The Moon has a mass of about .
Some people think there is no gravity on the Moon. Are they
correct? Use the information in this question to explain why.
Weight
The force of gravity on an object is called
its weight.
It is difficult to lift a heavy object because
gravity is pulling it towards the centre
of the Earth. By lifting, you are pulling
against gravity.
Weight is a force and it is measured in
newtons, N. The weight of an apple is
about 1 N. That means gravity from the
Earth is pulling on the apple with a force
of 1 N. You need to apply a force of 1 N
to hold the apple.
The force of gravity is making it difficult to hold these weights.
You can see the effect of the force bending the bar.
The weightlifter in the picture is holding
about !
Updated version of this
was supplied in July
(muted character smiles)
The contact force
When a book with a weight of 5 N is
resting on a desk, gravity is still pulling it
down with a force of . So why is the book
not moving down through the desk?
Tech-Set: This is the only
version we have been
supplied. Please advise
The answer is because the desk is
pushing back up on the book with
an equal force of .
This force from the desk is called the
contact force. The contact force acts up
from any surface to support an object.
The contact force is always equal to the
weight of the object when the surface is
not moving.
Sometimes the weight of the object is
larger than the contact force. If this
happens, the surface will break, or the
object will sink into the surface.
Your weight pulls you down, but an equal contact force pushes
you up.
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3 Forces and energy
The weight of this car is greater than the contact force from the sand.
Can you think of any other examples where the weight of an object is
larger than the contact force? Discuss your answers in pairs.
Questions
5
The diagram shows a box on a desk. Copy this diagram.
box
desk
On your diagram:
6
a
add an arrow to show the weight of the box. Label this
arrow W.
b
add an arrow to show the contact force from the desk.
Label this arrow C
A large rock rests on the ground. The weight of the rock
is 8000 N.
Write down the size of the contact force from the ground.
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3.1 Gravity, weight and mass
7
An elephant is standing on four feet. The weight of the elephant
is 40 000 N
Calculate the contact force from the ground on each of the
elephant’s feet.
8
A car travels into soft mud. The contact force needed to support
each wheel is 24 000 N
a
At first, the contact force from the mud on each wheel is
2000 N. Explain why the wheels will start to sink.
b
The contact force from the mud increases with depth.
Explain what will happen to stop the wheels sinking.
Weight and mass
Weight is the force of gravity on an object. It is measured in newtons, N.
Mass is the quantity of matter in an object. It is measured in kilograms, kg.
People often confuse mass with weight. They often say things such as:
‘The weight of my bag is 10 kg.’ This sentence is not correct because it
makes a statement about weight, but gives a mass. The correct sentence
is: ‘The mass of my bag is 10 kg.’
On Earth, the force of gravity is 10 N on every 1 kg of mass.
W
Writing this as an equation:
weight (N) = mass (kg) × 10 (N/kg)
or, using letters:
W = m × 10
m × 10
You can use a formula triangle for this equation.
To use a formula triangle, cover the part of the equation that you want
to find. Then, do the calculation that is shown in the uncovered part.
For example, if you want to find the mass, you cover .
The uncovered part is then
W
10
Divide the weight by 10 to get the mass.
Remember that m must be in kg.
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3 Forces and energy
The force of gravity that pulls on 1 kg tells you the strength of gravity.
On Earth, this is 10 N
As 10 N acts on 1 kg, you say this as ‘10 newtons per kilogram’,
or 10 N/kg. For example, if a person has a mass of 45 kg, their weight
on Earth is 45 × 10 = 450 N.
You can use the equation to calculate mass if you know the weight. For
example, a computer games console has a weight of 28 N. The mass of
the console is 28 = 2.8 kg.
10
The strength of gravity is not 10 N/kg in all parts of the Solar System.
The diagram shows the strength of gravity in some other parts of the
Solar System.
Moon Jupiter 25 N/kg
Earth 1.6 N/kg
10 N/kg
Mercury
3.7 N/kg
Venus
8.9 N/kg
Saturn
10 N/kg
Mars
3.7 N/kg
The weight of an object changes when the strength of gravity changes.
If you want to calculate your weight somewhere other than Earth, you
can use the same equation but you must change the number 10 to the
value of the strength of gravity wherever you are calculating it.
The mass of an object does not change.
Questions
9
The strength of gravity is 10 N/kg on Earth.
a
Calculate the weight of an adult who has a mass of 75 kg.
b
Calculate the mass of a car that has a weight of 8500 N.
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Uranus
8.7 N/kg
Neptune
11 N/kg
3.1 Gravity, weight and mass
10 Use the information in the diagram of the planets on the previous
page to answer these questions.
a
Give the location where your weight would be greatest.
b
Name the planet where you would have the same weight as
on Earth.
c
Calculate the weight of a 25 kg mass on Mars.
d
Explain how your mass on Earth would compare with your
mass on Mercury.
11 When you stand on scales you see your mass in kg. Explain whether
it is your mass or your weight that makes the scales work.
Discuss your answer with a partner.
12 In 1969, a spacecraft carrying people went from the Earth to the
Moon. The people explored part of the Moon. The spacecraft then
brought the people back to Earth.
Explain why a larger force is needed for a spacecraft to go from
Earth to the Moon than to come back from the Moon to the
Earth. Use the information in the diagram. Assume the mass of the
spacecraft is the same on both journeys.
Activity
Mass or weight?
On a large piece of paper, draw a table with two columns: one for mass and one for
weight.
Each of the statements below should start with either the word ‘mass’ or the word ‘weight’.
Work in pairs to decide which column to put each of the statements in.
When you have decided, write the statement in the appropriate column.
The statements are:
… of an object is affected by the strength of gravity on a planet.
… is measured in newtons, N.
… is measured in kilograms, kg.
… is not affected by gravity.
… of an object decreases as the object moves further away from Earth.
… is the quantity of matter in an object.
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3 Forces and energy
Continued
… can be measured in grams, g.
… is the force needed to lift an object.
… is equal to the contact force on a level surface that is not moving.
… is the property of a planet that makes it have gravity.
•
How did you decide which statements were about weight
and which were about mass?
•
Did your strategy work?
•
Could you use this strategy again, or would you change it?
Think like a scientist
Linking weight and mass
clamp stand
In this investigation, you will find the weights of
some masses and draw a graph of your results.
force meter
You will need:
• force meter
• clamp stand
• mass hanger and masses
Set up the equipment as shown in the
diagram.
1
Start by hanging the force meter from
the clamp stand. Leave enough space
to hang the masses, remembering
that the spring will extend.
masses
on hanger
Finding the weight of a mass.
2
Hook the mass hanger to the force meter. Record all your results using the kg unit for
mass. Remember that is .
3
Using the force meter, carefully measure the weight. Remember that this result is in
newtons, N.
4
Increase the mass by adding one mass at a time. (That is the same as adding each
time.) Use the force meter to measure and record the weight after every increase.
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3.1 Gravity, weight and mass
Continued
5
Record the weights in a table. Remember to put the units in the column headings
and not in the table itself.
6
Measure the weights as accurately as possible. Being accurate means being close
to the true value.
7
Your results should go from up to .
8
Draw a line graph of your results. Put mass in kg on the horizontal axis and weight
in N on the vertical axis.
Questions
1
When you have finished your graph, copy and complete these sentences.
As the mass gets bigger, the weight gets … .
When the mass doubles, the weight … .
2
Is the weight of 1.0 kg exactly 10 N as in the equation W = m × 10? If not, what
is the weight of 1.0 kg?
3
The strength of gravity at the Earth’s surface varies slightly between 9.7639 and
9.8337 N/kg
Explain why you can use the value of instead of these more accurate values.
Self-assessment
1
For each of these statements about your experiment, decide how well you
think you did.
•
I worked safely, taking care not to drop any masses or knock the clamp
stand over.
•
I took the reading from the force meter as accurately as possible.
•
I continued to record actual results, even when I thought I could see a
pattern developing.
•
I wrote down or drew my results clearly, so that someone else could
understand them.
•
I made my graph accurate and clear.
2
Write down one thing that you did really well.
3
Write down:
•
one thing that you could do better next time
•
how you will try to improve next time.
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3 Forces and energy
Summary checklist
I can describe why objects such as planets have gravity.
I can describe how the force of gravity acts around the Earth.
I can describe weight as the force of gravity on an object.
I can describe mass as the quantity of matter in an object.
I can understand the difference between weight and mass.
I can use the mass of an object and the strength of gravity to
calculate weight.
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3.2 Formation of the Solar Systemaxis
3.2 Formation of the
Solar System
axis
In this topic you will:
•
learn about how scientists think the Solar System was formed
•
think about objects in space growing larger and increasing in
mass
•
understand that as these objects increase in mass, their
gravity increases
•
understand that as their gravity increases, they can attract
even more mass.
Getting started
Key words
Choose one correct answer to each question.
axis
contradict
evidence
formed
model
nebula
observe
orbit
plane
spin
support
1
An object causes a strong force of gravity. What must the
object have?
large size
2
small size
small mass
Which of these objects has the largest mass in the Solar
System?
Earth
3
large mass
Jupiter
Sun
Neptune
Which of these objects is at the centre of the Solar System?
Earth
Moon
Mercury
Sun
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3 Forces and energy
Where did the Solar System
come from?
When the Solar System formed, there were no people to observe how it
was made. Observe means to watch something happening. So how do we
know what happened?
Scientists can try to solve a problem like this in two different ways.
•
They can look for evidence, in the form of facts from observations
or experiments to support their theory, and then try to explain what
they have found.
•
They can think of a testable theory, called an hypothesis, and then
look for evidence to support the hypothesis.
Facts about the Solar System
Look at the diagram of the Solar System.
Neptune
Jupiter
Earth
Mercury
Venus
Mars
Uranus
Saturn
The Solar System.
Here are some facts about the Solar System:
•
All the planets in the Solar System follow a path or orbit around the
Sun in the same direction.
•
The Sun and all the planets (except Venus and Uranus) spin on their
axes (singular: axis) in the same direction.
•
Most of the moons of the planets orbit their planets in the same
direction as the planets rotate around the Sun.
•
The direction of spin of the Sun and the planets (except Venus and
Uranus) is the same as the direction in which the planets orbit the Sun.
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Where did the Solar System come from?
•
All the planets orbit the Sun in the same plane. Objects that are in
the same plane could all be placed on the same flat surface, just like
all the objects on a desk. That means the Solar System looks flat.
Scientists can use these facts as evidence.
Watching the birth of stars
Scientists can see distant stars forming
in other parts of space. These stars are
being formed from clouds of dust
and gas.
A cloud of dust and gas in space is called
a nebula. The picture shows one of these
clouds of dust and gas. You can see the
young stars in the cloud.
Some young stars can also be seen with
a flat disc of dust around them.
Scientists think our Solar System was
formed this way.
Using models
The Orion Nebula – stars are being born here.
Scientists cannot observe a star or Solar System forming in an experiment.
Instead they use computers to create models. A model is a way of
representing something that is difficult to observe directly.
The scientists put many of the known laws of physics into a computer
program. Then the computer uses this information to predict what will
happen, starting with a cloud of dust and gas.
The result is a prediction that a star will form, surrounded by planets.
How do stars and planets form out of dust
and gas?
The picture shows what scientists think our Solar System looked like
as it was forming.
You saw in Section 3.1 that any object can act as a source of gravity.
All the particles of dust and gas in the pictures have their own
weak gravity.
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3 Forces and energy
The particles of dust and gas pull on each
other with very weak forces due to their
own gravity. As they stick together, their
total mass increases. As their mass increases,
so does the strength of their gravity. That
means they attract more dust and gas with a
stronger force.
This starts to form a small ball.
Gradually, this ball gets bigger.
If the ball gets beyond a certain size, it will
get hot enough to become a star. Otherwise
it will become a planet.
Most of the facts about the Solar System
support or agree with this hypothesis.
This is how our Solar System may have looked 4.6 billion years ago.
The fact that Venus spins on its axis in the
opposite way to all the other planets seems
to contradict this hypothesis. Contradict is
the opposite of support – it means to go against something.
Scientists think the planet Jupiter almost reached the size to be a star.
It takes millions of years to form a star or a planet.
Questions
1
Use words from the list to copy and complete this sentence.
different directions
the same direction
opposite directions
random directions
All the planets in the Solar System orbit the Sun in ….
2
All the planets in the Solar System orbit the Sun in the same plane.
Explain what ‘the same plane’ means.
3
Which of these is the name given to a cloud of dust and gas in space?
planet
4
star
nebula
moon
Name the force that can pull particles of dust and gas together
in space.
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Where did the Solar System come from?
Activity
Solar System story board
Work in groups.
Use a large piece of paper to make a storyboard to tell people about how the Solar
System formed. A storyboard is a series of drawings that tell a story. There can be
writing with the drawings.
In your storyboard you should show:
•
a nebula and what it contains
•
how a star such as the Sun forms
•
how planets form around the Sun.
Include in your storyboard reasons why:
•
all planets orbit the Sun in the same direction
•
most of the planets spin on their axes in the same direction.
Self-assessment
1
For each of these statements about your experiment, decide how well you think
you did.
•
I contributed ideas to the group.
•
I worked in a team, cooperating with others.
•
I thought the storyboard communicated ideas clearly.
2
Write down the most interesting thing you learned about the formation of the Solar
System.
3
Write down one thing that still puzzles you about the formation of the Solar System.
Think like a scientist
Using models
In this task you will be thinking about how scientists use models and how they use
an hypothesis.
Scientists use computers to model how the Solar System was formed.
One reason for using a model is that it takes millions of years to form a star and
planets from a cloud of dust and gas. A model can speed this up.
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3 Forces and energy
Continued
Questions
1
Suggest one other reason for using a model in this way.
2
Models are not real, so may not be accurate.
Which term describes this?
an error
3
a mistake
a limitation
a strength
Look at the facts about the Solar System given earlier in this section.
Scientists use facts like these to support their hypothesis of how the Solar System
formed. An hypothesis is a theory or idea that is testable.
4
a
Give two facts about the Solar System that seem to contradict this hypothesis.
b
Explain why these facts seem to contradict the hypothesis.
Which two of these statements describe the hypothesis of how the Solar System formed?
•
It has been proven to be correct.
•
Most, but not all, of the evidence supports it.
•
The model that is used has limitations.
•
It can be fully tested by experiments.
Summary checklist
I can recall that there are clouds of dust and gas in space.
I can recall that stars and planets are formed from dust and gas.
I can understand that gravity can pull particles of dust
and gas together.
I can describe how stars and planets are formed.
I can understand how scientists use a model to test
an hypothesis.
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3.3 Movement in space
3.3 Movement in space
In this topic you will:
•
learn about what keeps the planets in orbit around the Sun
•
understand why planets move at different speeds
•
discover why objects moving in space do not slow down as
they do on Earth.
Getting started
Key words
1
Write the names of the planets in order, starting with the one
that is closest to the Sun.
2
Name the object that orbits the Earth and not the Sun.
air resistance
circlar
speed
vacuum
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3 Forces and energy
The Sun
In Section 3.1 you saw that objects with more
mass have more gravity.
The Sun is the object with the largest mass in
the Solar System.
The mass of the Sun is times greater than the
mass of the Earth. In fact, the mass of the Sun
is more than the mass of all the other planets
added together!
The strength of gravity on Earth is . On the
Sun it is .
The Sun’s gravity
The Sun’s gravity is 27 times stronger than
the Earth’s gravity.
It holds all the planets in their orbits. The Sun’s
gravity gets weaker as the distance from the
Sun increases.
This photograph of the Sun was taken from a spacecraft,
using a special camera. You should never look directly at the
Sun or try to photograph it yourself.
The planet Neptune is 30 times further from the Sun than Earth is.
The mass of Neptune is about 17 times the mass of Earth. So although
the Sun’s gravity gets weaker, it is strong enough to hold Neptune
in orbit.
direction of
orbit
planet
direction of force
from the Sun’s
gravity
Orbits of planets
The orbits of the planets, including Earth, are
almost circular. Circular means in the shape of
a circle.
Sun
To keep any object moving in a circle, there needs
to be a force causing it to turn.
The diagram shows how the force of gravity acts
on a planet to keep it in orbit.
The force of gravity from the Sun that acts on a
planet always acts towards the Sun.
If this force did not act in this way, the
planet would travel off in a straight line
into space!
The force of gravity from the Sun keeps a planet in orbit.
The diagram is not to scale.
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3.3 Movement in space
Mercury, which is the closest planet to the Sun, has the strongest pull
from the Sun’s gravity.
This causes Mercury to orbit with the highest speed of all the planets.
The average speed of Mercury around the Sun is 170 000 km/h! The
average speed of the Earth around the Sun is about 100 000 km/h.
Speed in space
On Earth, all objects that move have forces
acting on them to slow them down.
Air resistance is one of those forces.
It is caused by a moving object having
to push against the particles in the air.
Air resistance acts in the opposite direction
to movement.
The faster an object moves, the greater the
air resistance on the object.
Look at the picture of the aeroplane wing.
The aeroplane can slow down faster with extra
air resistance. The shape of the wing can be
changed to produce extra air resistance.
This aeroplane has landed and is using extra air resistance to help
it slow down.
In space there is no air. There are very, very
few particles in space. A space where there
are no particles is a vacuum.
Look at the spacecraft in the picture.
This spacecraft, called the Juno probe,
would have a lot of air resistance if it were
moving on Earth.
In space, where there is a vacuum and no
air resistance, the Juno probe reached a
speed of as it passed Jupiter. It became the
fastest object that people had ever made.
This speed would not be possible for
the Juno probe on Earth because of air
resistance.
Earth and the other planets are also moving
in a vacuum. This means there is no air
resistance to slow them down.
This spacecraft reached a speed of in July 2016.
The only force acting on the planets is from gravity.
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3 Forces and energy
Questions
1
State the direction in which the force of gravity from the Sun pulls
on a planet.
2
Other objects, such as comets and asteroids, also orbit the Sun.
Suggest what keeps these other objects in orbit around the Sun.
3
The Sun has the strongest gravity in the Solar System.
Suggest which object in the Solar System has the second
strongest gravity.
Discuss your answer in pairs.
4
State the word used to describe a space that has no particles in it.
5
Voyager 1 is a space probe launched in 1977. Voyager 1 is now
outside the Solar System and is travelling at . Explain why Voyager 1
could not travel at this speed on Earth.
6
Which of these forces acts on the Earth as it orbits the Sun?
gravity only air resistance only gravity and air gravity, air resistance
resistance and friction
7
The orbits of the planets are not exact circles. The distance from the
Sun of each planet varies slightly as it goes around in its orbit. This
change in distance makes the speed of the planet change slightly.
Suggest how the speed of a planet changes with distance from the
Sun during its orbit.
Activity
Planet speeds
The table shows the average speed of each planet’s orbit around the Sun.
The speeds are given in kilometres per second (km/s) as they are so fast.
Name of planet
Speed of orbit in km/s
Mercury
48
Venus
35
Earth
30
Mars
24
Jupiter
13
Saturn
10
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3.3 Movement in space
Continued
Name of planet
Speed of orbit in km/s
Uranus
7
Neptune
5
Use the information in the table to draw a bar graph.
Put the names of the planets, in order from Mercury, across the horizontal axis.
Space them evenly so your bars are not touching.
Questions
1
2
3
4
Copy and complete the sentence.
As the distance from the Sun increases, the speed of orbit of the planets … .
Explain the advantages of presenting this information in a graph rather than in a table.
Explain the reason for the trend in your graph.
Explain why a bar graph is used for this information rather than a line graph.
Self-assessment
1
For each of these statements about your activity, decide whether you did it very well,
fairly well or not at all.
•
I drew a bar graph with the correct information.
•
My bars were evenly spaced and not touching.
•
All my lines were drawn with a pencil and ruler.
•
All my bars were the correct height.
•
I understood the advantages of drawing a graph to display information.
2
Write down one thing that you did really well.
3
Choose one thing that you think you could do better next time and explain how you
will try to improve it.
Think like a scientist
Discovering planets
In this task you will find out about how scientists discovered the planet Neptune.
The planet Uranus was discovered in the year 1781. It was thought to be the most distant
planet from the Sun.
In 1821, a French scientist called Alexis Bouvard made calculations about the orbit of
Uranus. He worked out where Uranus would be at different times.
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3 Forces and energy
Continued
1
Which one word best describes these calculations?
The actual orbit of Uranus was different to the calculations.
observations
2
predictions
conclusions
measurements
The planet was seen to move further away from the Sun at regular times.
These results were recorded.
Which word best describes these results?
observations
3
predictions
conclusions
secondary information
Scientists thought that another source of gravity was pulling Uranus further
from the Sun.
Which word best describes this statement?
observation
4
conclusion
measurement
secondary information
Scientists then made predictions about another planet further away than Uranus.
They used the results from the orbit of Uranus to predict where this other planet
would be.
Then, in 1846, scientists found another planet, which they called Neptune.
Neptune was very close to where they predicted it would be.
5
Use words from the list to copy and complete these sentences.
Uranus moving further away from the Sun
about its orbit.
the original prediction
Scientists found Neptune using careful
testable
a fair test
contradicted
results
conclusions
supported
observations
measurements
Summary checklist
I can name the force that keeps the planets in orbit around the Sun.
I can describe the direction that this force acts on a planet.
I can understand why planets closer to the Sun move faster.
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3.4 Tides
3.4 Tides
In this topic you will:
•
find out what tides are
•
learn about tidal forces and where they come from
•
discover how tidal forces affect the oceans and the land.
Getting started
Key words
Work in groups to answer these questions.
coastal
depth
earthquake
earth tide
force of
attraction
harbour
tidal force
tidal range
tide
1
Which object has the strongest gravity in the Solar System?
2
What large object orbits the Earth?
3
What force keeps the object that orbits the earth in its orbit?
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3 Forces and energy
What are tides?
In some parts of the world, the depth of the ocean changes by several
metres during the day. The depth is the distance from the surface of the
water to the bottom of the ocean.
The picture shows the same place at two different times. The pictures
were taken six hours apart.
This change in depth of the water is called a tide.
Tides change the depth of the oceans. High tide (left) and low tide (right) are six hours apart.
The difference in depth of the water between high and low tides is
the tidal range.
The largest tidal range in the world is 16.3 m in the Bay of Fundy
in Canada.
Some of the smallest tidal ranges in the world are less than in the
Caribbean and Mediterranean seas.
Tides also cause the land to change in height through the day! This is
called earth tide. The tidal range due to earth tide is about 30 cm
High tides are about 12 hours apart. Low tides are also about 12 hours
apart. The time between high and low tide is six hours.
What causes tides?
The Moon orbits the Earth.
The Moon stays in orbit because of the force of gravity from the Earth
but the Moon also has gravity, and this gravity pulls on the Earth.
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What are tides?
As the oceans are made from water,
the gravity from the Moon can pull
the water more easily than the land.
The pull from the Moon’s gravity
is called a tidal force. The diagram
shows how this happens.
low tide
direction of Earth
spinning on
its axis
high tide
Moon
high tide
Look at the drawing of the Earth
and Moon. The Earth is viewed
from above the North Pole.
pull of gravity
from the Moon
The side of the Earth closer to the
Moon will have high tide.
low tide
The Earth takes 24 hours to spin on
its axis.
The blue line around the Earth represents the ocean depth. The difference
in depth is caused by the pull of gravity from the Moon. The drawing is not
to scale.
This means that 12 hours later, the
side that was closest to the Moon is
now furthest away.
You can see from the drawing that the side furthest away also has a
high tide.
This is why the time between high tides is 12 hours.
The Sun also produces a tidal force on Earth, but this is weaker as the
Sun is further away than the Moon.
When the Sun and the Moon are in line with Earth, this produces a
larger tidal force.
The next drawing shows how this happens.
greater tidal range when
Earth, Moon and Sun
are in line
pull of gravity from the
Sun and the Moon
Moon
Sun
Larger tidal forces affect the Earth when the Earth, Sun and Moon are in line. The drawing is not to scale.
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3 Forces and energy
Effects of tides
Some harbours can only be used at certain times of the day. If the water in
the harbour is not deep enough, boats cannot move safely. Harbours are
places where boats and ships can load and unload passengers and cargo.
In weather with strong winds, coastal areas are more likely to have
flooding at times of high tides. Coastal areas are parts of the land that
are close to the oceans.
The flow of water in and out of some coastal areas can be dangerous for
small boats.
In some places, tides affect food chains, including the human food chain.
For example, at low tide birds can eat some types of shellfish when
they are not covered with water. Some types of fish move to find food
according to tides in coastal areas.
Volcano eruptions have been linked with earth tides. By studying
Earth tides, scientists may be able to predict when a volcano will
become dangerous.
Earthquakes may also be linked with earth tides.
Movement of water with tides can be used to generate electricity.
Questions
1
Which of these causes the force of gravity for tides on Earth?
2
the Sun only the Moon only the Sun and Moon the Sun, Moon and other stars
What is the name given to the pull of gravity that causes tides?
high tide
3
low tide
tidal range
tidal force
State the time between:
a
one high tide and the next high tide
b
one low tide and the next low tide
c
a high tide and the next low tide.
4
Explain why some harbours cannot be used at low tide.
5
Explain why the largest tidal ranges happen when there is either a
full moon or a new moon.
6
The average depth of water in a place near the coast of the Pacific
ocean is .
The largest tidal range in that place is .
Calculate the maximum depth of water at that place.
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What are tides?
Activity
Investigating tides
Work in groups.
You will need:
card or paper, some circles to draw around, scissors
Cut out a small, a medium and a large circle. Label these ‘Moon’, ‘Earth’ and ‘Sun’ in
order of increasing size.
Next, cut out two thin crescents that will fit around your Earth, as shown here.
Call these two crescents ‘set 1’.
Now, cut out two thicker crescents that will also fit around your Earth, as shown here.
Call these two crescents ‘set 2’.
The crescents represent the ocean depth around the Earth.
Part 1: Why tides happen
For part 1, you do not need the shape that represents the Sun. Set it to one side for now.
Put the Earth and Moon on a desk about away from each other. This is not to scale.
Now put the crescents that represent the ocean depth, set 1, on either side of the Earth.
The deepest parts should be in line with the Moon.
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3 Forces and energy
Continued
Question
1
Why are the deepest parts of the oceans in line with the Moon?
Part 2: Times of the tides
Mark a point at the coast on your Earth. The activity will work best if you choose a
point close to the edge of the circle, which is the equator.
Now, slowly turn your Earth. You should turn it in the opposite direction to the
movement of the hands on a clock. You should only turn the Earth, not the ocean
depth shapes as well.
Questions
2
How many high tides does your chosen point get in one full rotation?
3
How many low tides does your chosen point get in one full rotation?
4
The Earth takes 24 hours to rotate once like this. Try to use the model to explain why:
5
a
high tides are 12 hours apart
b
low tides are 12 hours apart.
The Moon does not stay in one place like this. It orbits the Earth.
The Moon orbits the Earth in the same direction as the Earth rotates on its axis.
The Moon takes 27 days to orbit Earth once.
a
Explain whether high tides will happen at the exact same time each day.
b
Try to work out how much earlier or later high tides will be each day.
Part 3: Why tidal range also depends on the Sun
For part 3 you will need your shape that represents the Sun.
You will need to change the ocean depth shapes to set 2.
Put your Earth, Moon and Sun in a line like this (it is not to scale).
Earth
Moon
Sun
Questions
6
Can you explain why set 2 is now better than set 1 to show what happens with tides?
7
Name this phase of the Moon as it appears from Earth in this position.
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What are tides?
Continued
8
Now move the Moon to the other side of the Earth, but keep the Moon, Earth and
Sun in line.
Name this phase of the Moon.
9
a
hat can you conclude about the times when the highest tides happen, in terms
W
of how the Moon appears?
b
The length of time taken by the Moon to orbit Earth is called a lunar month. How
many of these highest tides will occur each lunar month?
Self-assessment
In your groups, discuss each of these questions.
•
What was my role in the group?
•
How did my role help me understand the tides?
•
How did other people in the group contribute to my understanding?
Think like a scientist
Discovering the causes of tides
In this task, you will find out about how scientists used evidence to discover what
causes tides.
In 330 BCE, a sailor from Greece noticed that the depth of water in some parts of the
oceans changed regularly.
He noticed that the depth increased to a maximum twice every day.
He thought that this was because of the Moon.
People did not know about gravity until much later.
1
Use words from the list to copy and complete the sentences.
a conclusion
an observation
a prediction
a measurement
an explanation
a model
The sailor noticed that the depth of water changed. This was
.
The sailor thought that the change was caused by the Moon. This was
The sailor did not know about gravity, so could not give
.
. for the tides.
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3 Forces and energy
Continued
Around the year 1600, a scientist from Germany suggested that there was a force of
attraction between the Moon and water. He thought this force caused the tides.
People in 1600 did not know about gravity.
This German scientist said that the force of attraction was magnetic.
We now know that the attractive force between the Moon and the water in the oceans
is not magnetic.
2
Describe what could be done to show that there is no magnetic force between the
Moon and water in oceans.
People did not believe that the Moon or the Sun could have an effect on the oceans
because gravity had not been described.
The problem of what causes tides was finally solved by Newton in the year 1687.
Newton had already described the effects of gravity.
He then used his ideas about gravity to calculate the tidal forces, without the need
for experiments.
These calculations were accurate enough to show people that gravity from the Moon
and the Sun caused the tides.
People then accepted that tidal forces were caused by gravity from the Moon and
the Sun.
3
Which two statements explain why people accepted Newton’s ideas about gravity?
•
Newton did experiments on the tides that were fair tests.
•
Newton provided evidence to support an hypothesis.
•
Newton made observations whereas previous scientists did not.
•
Newton made predictions that were shown to be accurate.
Summary checklist
I can understand what tides are.
I can understand where tidal forces come from.
I can explain the part played by the Moon in causing tides.
I can explain the part played by the Sun in causing higher tides.
I can understand why there are two high tides and two low tides
every day.
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3.5 Energy
3.5 Energy
In this topic you will:
•
find out what energy is
•
learn about different energy stores and transfers
•
discover how some ways that energy can be stored more
easily than others.
The sentence at the second
bullet point makes no sense.
Author to rewrite it.
Tech-Set: there is no
information for the 3rd bullet
point in the query log!
Getting started
Key words
With your partner, make a list of:
chemical
elastic potential
electrical
energy
fuel
gravitational
potential
joule
kinetic
light
luminous
sound
stored
thermal
transferred
1
some things that you need energy to do
2
some of the types of fuel that you know.
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3 Forces and energy
What is energy?
Energy is something that must be changed or transferred in order to
do something.
There are many different ways that energy can be stored or transferred.
For example, kinetic energy is the energy in movement.
The unit for measuring the amount of energy is called the joule (J).
You need about:
•
•
•
to walk up the stairs between two floors in a building.
for every metre you run
to bring 1 litre of cold water to boiling point.
Energy stores and transfers
There are many different ways in which energy is being stored or
transferred around you all the time.
These runners have kinetic energy as they are moving.
The table describes some of these stores and transfers.
energy
description
energy store or energy transfer
kinetic
energy stored due to movement
of an object
store
chemical
energy stored in food, batteries,
chemical fuels such as wood, oil
and coal
store
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3.5 Energy
energy
description
energy store or energy transfer
thermal
heat energy stored in hot objects
and transferred to colder objects
store or transfer
elastic potential
energy stored when things are
stretched or squeezed to change
their shape
store
gravitational
potential
energy stored when an object
is lifted away from a source
of gravity
store
electrical
the flow of current in a circuit
transfers electrical energy
transfer
sound
energy transferred from
vibrating objects
transfer
light
visible energy from luminous
objects (objects that give
out their own light) that you
can see
transfer
Look at the descriptions of energy in the picture.
chemical – the
bus carries fuel
kinetic – the bus is moving
electrical – for lights
thermal – the engine
is hot
sound – the engine
makes noise
gravitational potential –
the bus is going uphill
elastic – the tyres get squeezed
This bus has many types of energy.
•
How will you learn the different stores and transfers of energy?
•
Can you think of a way to help you remember them?
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3 Forces and energy
Storing energy
Energy can be stored more easily in some ways
than in others.
For example, you can keep uncooked rice for a
long time. That is a store of chemical energy.
Coal and crude oil are stores of chemical energy
that formed millions of years ago. This shows that
some energy stores can last for a very long time.
A battery is another example of how chemical
energy can be stored. It is quite easy to store
chemical energy.
Gravitational potential energy is also easy to
store. The picture shows a tank containing water.
A pump has been used to lift up the water. The
water stores gravitational potential energy.
The tennis ball has a store of kinetic energy while it
is moving.
Some energy stores only last for a short time.
Thermal energy (heat) is one example. Hot objects will eventually cool
down (they will lose their store of thermal energy).
Kinetic energy is another example. Kinetic energy is more difficult than
chemical or gravitational potential energy to store.
The tennis ball in the picture has a store of kinetic energy while the ball
is moving, but the ball will eventually stop moving.
Rice is a store of chemical energy.
The tank contains water that has been lifted up by a
pump. The water in the tank stores gravitational
potential energy.
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3.5 Energy
Questions
1
Look at the picture of the circuit.
Copy and complete these sentences. Choose from the
stores and transfers of energy you have learnt about.
2
3
a
energy is stored in the battery.
b
energy is transferred in the wires.
Name the energy store in each of these. There may
be more than one for each.
a
food
b
gasoline (petrol)
c
a falling rock
d
a book that has been lifted up onto a shelf
a
Name two energy stores that will last for a long time.
b
Name one energy store, apart from thermal energy, that will not
last for a long time.
4
Describe an example that shows thermal energy cannot be stored for
a long time.
5
The human population in the world is growing. Many countries are
developing rapidly.
Explain how this is affecting the amount of energy being used in the world.
Use some examples of different energy stores and transfers in your answer.
Discuss your answer with a partner.
Activity
Finding energy stores and transfers
You will need some magazines with pictures that can be cut out.
Work in pairs or small groups.
Look for pictures that show different energy stores and transfers.
Some pictures may show more than one.
Cut out the pictures.
Stick the pictures on a large sheet of paper to make a poster.
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3 Forces and energy
Continued
Your poster should show as many energy stores and transfers as possible.
Make sure the energy stores and transfers in each picture are clearly labelled.
Peer assessment
Swap posters with another group.
1
Does the poster show all the energy stores and transfers?
2
Are all the energy stores and transfers clearly labelled?
3
What did you like about the other group’s poster?
4
Suggest one way that the other group might be able to improve their poster.
Summary checklist
I can recall the ways that energy is stored and transferred.
I can describe each energy store and energy transfer.
I can give examples of each energy store or transfer.
I can understand that some energy stores last longer than others.
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3.6 Changes in energy
3.6 Changes in energy
In this topic you will:
•
learn about energy changing
•
discover that energy changes when something happens
•
learn how to give examples of changes in energy.
Getting started
Key words
1
Make a list of all the energy stores and transfers that you
can remember.
2
Give an example of each store or transfer on your list.
change
event
process
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3 Forces and energy
How does energy change?
In Section 3.5, you learned that energy is something
that must be changed or transferred in order to
do something. Before energy can be changed or
transferred, it is stored. When energy is stored, the
energy is not doing anything.
The picture shows a cooking pot being heated
on a fire.
The fuel for the fire is wood. Wood is a store of
chemical energy.
Burning the wood changes the chemical energy
to thermal energy (heat).
The thermal energy is then transferred
to the pot and the food inside.
The people in the picture are walking up stairs.
They are changing chemical energy from their
food into kinetic energy for movement.
The movement is taking the people higher, so
kinetic energy is being changed to gravitational
potential energy.
Energy changes can be useful.
This picture shows a power station.
This power station is changing energy.
Walking up stairs needs energy to be changed.
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How does energy change?
This power station is using the chemical energy stored
in natural gas.
The gas is burned, which changes chemical energy to
thermal energy.
The thermal energy is then changed to kinetic energy
in large generators that spin around.
The kinetic energy is then changed to electrical energy.
The electrical energy is then transferred through wires
into homes and buildings.
Energy changes are not always helpful. Typhoons,
hurricanes, earthquakes and tsunamis are some
examples of how energy changes can be very dangerous.
In all these examples, there is a process or event that
changes or transfers the energy. For example, burning
is a process.
Strong wind can transfer energy in a damaging way.
Burning changes chemical energy stored in a fuel to thermal energy.
You can represent the processes as arrows and draw diagrams to show
changes in energy.
Here are some other examples.
A fire that burns wood changes chemical energy to thermal energy.
chemical
thermal
A television converts electrical energy to sound and light.
sound
electrical
light
When a book falls from a shelf, that is an event. When the book is on
the shelf, the book has stored gravitational potential energy. This energy
is changed to kinetic energy as the book falls.
You can also represent events such as this in a diagram.
gravitational potential
kinetic
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3 Forces and energy
The energy changes shown in these diagrams are useful energy changes.
That means the energy is changed in a way that we want.
Some energy changes are not useful. You will learn more about energy
that is not useful in Section 3.7.
Questions
1
Copy and complete the sentence.
When something happens, energy is
2
or
.
The useful energy change in a candle can be written as
chemical to light
Write down the useful energy change in each of these.
3
a
an electric lamp
b
a bus
c
a radio.
Draw diagrams to show the energy changes in:
a
a motorcycle that uses gasoline (petrol) for movement
b
a wood-burning fire used for cooking
c
a bird using movement to fly higher
d
a ball rolling down a hill.
Activity
Freezing water
Work in groups.
When you put water in the freezer, it turns into ice.
Discuss and then answer these questions about this process in your group.
1
What happens to the temperature of the water in the freezer?
2
How can you tell the temperature has changed in this way, without using a
thermometer or touching the water?
3
How is energy being transferred when the water freezes?
4
Where does this energy come from?
5
Where does it go?
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How does energy change?
Continued
Once you have agreed on your answers, ask your teacher to check them.
Make a display to show the energy change when water freezes.
Your display could be a leaflet, a poster or a presentation.
Your display should give other people the correct information as clearly as possible.
Think like a scientist
Candle energy
You will now do an experiment to investigate a change in energy. Work in pairs or
small groups.
You will need:
candle, safety glasses, glass beaker or a metal can, tripod and gauze, thermometer,
timer, heat-proof mat, stirring rod, cooking oil, matches
Set up the equipment as shown in
the diagram.
1
Measure the temperature of the
cooking oil and write this down.
2
Light the candle and place it under
the beaker. Start the stopwatch or
record the time.
3
Stir the cooking oil at regular
intervals. Use the stirring rod. Do
not stir with the thermometer!
4
Measure the temperature of the
cooking oil every minute. Record
both the time and the temperature.
5
Stop heating when the temperature
of the cooking oil has gone up by
10°C.
6
Carefully blow out the candle.
This has been amended to
include a lab coat, supplied in
July.
Tech-Set: new illustration has
not been supplied
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3 Forces and energy
Continued
7
Draw a table for your results.
8
Draw a line graph of your results. Put the temperature of the cooking oil on the
vertical axis.
Questions
1
Explain why you should not use a thermometer for stirring.
2
Explain where the energy came from to heat the cooking oil.
3
Describe what happened to the candle during the experiment.
4
In this experiment, not all of the thermal energy is transferred to the cooking oil.
List two other things that get heated in this experiment.
5
Suggest changes to this experiment to transfer more of the thermal energy into
the cooking oil.
6
Explain why a line graph is a better way to display the results from this experiment
than a bar chart.
Self-assessment
Discuss each of these statements with your partner or small group.
•
We worked safely at all times.
•
We recorded all the results at the right times.
•
We took readings from the thermometer as accurately as possible.
•
We put the correct column headings with units in the table.
•
We drew the graph correctly and it shows the trend in the results.
Summary checklist
I can understand that energy can be changed.
I can give examples of some changes in energy.
I can draw diagrams to show energy changes.
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3.7 Where does energy go?
3.7 Where does energy go?
In this topic you will:
•
discover that when energy is changed, some of it may
be wasted
•
learn that some of this energy can never be recovered.
Getting started
Key words
Work with a partner. Discuss the energy that is changed or
transferred in each of these processes.
dissipated
recovered
useful
wasted energy
•
Burning wood for cooking.
•
Walking up stairs.
•
Cycling on a level road.
In each case, state where the energy comes from and the useful
energy that is changed.
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3 Forces and energy
Useful and wasted energy
Every time you use energy to make something happen,
energy is transferred or changed. Some of the energy
transferred or changed is useful, but some of it is wasted.
Look at the picture of fuel being added to a motorcycle.
The motorcycle engine uses the chemical energy stored in
the fuel.
This chemical energy is changed to useful kinetic energy to
move the motorcycle and rider.
But chemical energy from the fuel is also changed into
thermal energy and sound energy.
In fact, only about 14 or 25% of the chemical energy in the
fuel is used for movement.
The other 34 or 75% of the energy is wasted energy. This
wasted energy is dissipated and cannot be recovered.
Dissipated energy is energy that spreads out where there is
no use for it.
You cannot gather thermal energy or sound and bring them
back into one place to be stored, changed or transferred.
Look at the two types of lamp in the picture.
A
Petrol (gasoline) is a store of chemical energy.
The motorcycle engine changes only some of
this into kinetic energy. The rest of the energy
is wasted.
B
These two lamps emit the same brightness of light but they waste very different
quantities of energy.
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3.7 Where does energy go?
Both lamps A and B in the picture change electrical energy to light
energy.
Lamp A only changes about 15% of the electrical energy into light. 85%
of the electrical energy is wasted as thermal energy from this lamp. This
is dissipated as thermal energy.
Lamp B changes about 50% of the electrical energy into light. 50% of
the electrical energy is dissipated as thermal energy from this lamp.
Every time energy is changed or transferred, there is some thermal
energy is wasted. This wasted thermal energy is dissipated.
Even when you want to produce thermal energy, some of it is wasted.
Look at the water being heated in
this picture.
In the picture, chemical energy from wood
is being changed to thermal energy by the
process of burning.
Thermal energy is being used to heat
the water.
Thermal energy is also being used to heat
the rocks, the metal container and the air
around it.
Some of the thermal energy is escaping in
the steam.
The fire is also changing energy into light.
All these represent wasted energy that is
dissipated and cannot be recovered.
Thermal energy from the fire is being used to heat water. Not all
of the thermal energy can be made to go into the water – some
of it dissipates.
For everything that uses energy change or transfer,
some of that energy will always be dissipated.
Questions
1
Which of these terms describes energy that is dissipated?
energy that spreads out and
becomes less useful
energy that becomes more
useful
energy that can be
used later
energy that is not useful but
can be stored
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3 Forces and energy
2
Which of these can be dissipated?
Choose all that are correct.
chemical
3
thermal
light
sound
elastic
List all the energy changes in these
processes.
List the energy as either useful or
wasted.
4
a
Using electricity in a lamp.
11
22
b
Using petrol (gasoline) in a
car engine.
Temperature
Temperature
Temperature
Temperature
c
Using electricity in a motor.
As you move away from a hot
object, you feel less heat from it. The
temperature will go down as you move
further away.
Which of these graphs shows how the
temperature changes with increasing
distance from a hot object?
Distance
Distance
Distance
Distance
33
44
Temperature
Temperature
Temperature
Temperature
Distance
Distance
•
How do you work out what the shape of a graph will look like?
•
Can you explain why you chose the answer that you did? You
can do this by describing what will happen to the temperature
in each case.
Activity
Ripple tanks
Work in groups.
You will need:
waterproof rectangular tray (about 40 cm × 20 cm × 5 cm), water, a ruler
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Distance
Distance
3.7 Where does energy go?
Continued
1
Put water into the tray so the water is about 1 cm deep.
2
Lift the short edge of the tray a little above the desk. Then drop the tray. You should
see a wave move across the water. The wave should start at the end that was dropped
and move towards the opposite end.
This has been amended to
change character to Zara.
Supplied in July. When located,
please ensure that ‘box’ is
changed to ‘tray’.
Tech-Set: new illustration has
not been supplied
drop this end of the tray
3
Count how many times the wave moves backwards and forwards across the tray
until you can no longer see it.
4
Change the depth of the water. Can you make the wave travel across the tray
any more times by changing the depth of water?
5
Now try making the wave go across the tray by lifting and then dropping the long
edge. Does the wave travel across the tray any more times in this direction?
Questions
1
State one variable that must remain the same when you change the direction of the
wave.
2
Which way (along or across the tray) does the wave travel the longest total distance?
3
Name the energy that is stored by the wave as it moves.
4
Use words from the list to copy and complete the sentence.
stays the same dissipates increases goes slower
As the wave travels, the energy in the wave ………………… .
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3 Forces and energy
Think like a scientist
Energy dissipation
In this task you will investigate the dissipation of energy.
You will need:
very hot tea in a cup, thermometer, plastic spoon,
timer or clock with a second hand
Safety
Take care not to scald yourself with the hot tea.
Work as a whole class.
Taking turns, measure the temperature of the hot tea every minute. Stir the tea before
measuring the temperature. Use the spoon, not the thermometer, to stir the tea.
Record the time and the temperature in a place where the whole class can see the results.
Questions
Work on your own to answer the questions.
1
Plot a line graph with time on the horizontal axis and temperature on the vertical axis.
Make sure your line is as smooth as possible. It should go through all of the points if
the temperatures have been measured correctly.
2
Describe the pattern shown in your graph. Use the words ‘temperature’ and ‘time’ in
your description.
3
Explain why you should stir the tea before measuring the temperature.
4
The higher the temperature of the tea in the cup, the more thermal energy there is in
the tea.
What do the results show about what happens to the thermal energy with time?
5
List some places where the thermal energy could have gone.
6
Suggest how you could:
7
a
make the tea cool more quickly, without adding anything into the tea.
b
make the tea cool more slowly, without heating it again and without adding more
hot tea.
Explain whether the tea in the cup will keep cooling, or whether it will stop cooling.
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3.7 Where does energy go?
Did you have any idea what shape the graph might be:
•
before you did the experiment?
•
when you looked at the temperatures that were recorded?
Summary checklist
I can recall that when energy is changed or transferred, some of
the energy is useful and some is wasted.
I can understand the meaning of the word ‘dissipate’.
I can understand that energy can be dissipated more easily in
some ways than in others.
I can understand that energy which has dissipated cannot
be recovered.
Project: Discoveries about energy
Background
string
James Prescott Joule was born
in the year 1818.
Joule was interested in how
things worked and where the
energy came from to make
things happen.
Joule made the machine shown
in the picture.
He used the machine in the
picture to show how energy could
be changed.
pulley
thermometer
water
paddle
mass
ruler
James Prescott Joule made this machine in the year 1845.
When the mass was allowed to
fall, it pulled on the string.
The string passed over a pulley and was wrapped around a piece of wood.
The piece of wood then rotated.
This made a paddle rotate.
The paddle rotated in water.
Joule discovered that when he did this, the temperature of the water increased.
Joule’s ideas and his results from experiments challenged the accepted ideas about
energy. His ideas were not accepted at first.
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3 Forces and energy
Continued
Your task
Make a presentation to tell others about how Joule’s machine works.
Your presentation should include this information:
•
The energy changes and transfers that happen in Joule’s machine.
You should include the terms:
•
•
gravitational potential
•
kinetic
•
thermal.
What did Joule’s result show?
You should use all these words correctly:
•
•
mass
•
weight
•
gravity
•
height.
You could finish your presentation by answering these questions.
Do you think all of the energy was changed in the way that Joule had wanted?
If not, where did any wasted energy go?
Why were the old ideas about energy eventually rejected and Joule’s
ideas accepted?
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3 Forces and energy
Check your Progress
3.1 Write the word used to describe each of these.
a
The force of gravity on an object.
[1]
b
The quantity of matter in an object.
[1]
Explain why the Sun has more gravity than any of the planets.
[1]
3.2 a
b
The strength of gravity on Earth is .
Calculate the weight of each of these.
Show your working and give the unit in your answer.
c
i
a book of mass [2]
ii
a calculator of mass [3]
In the year 1959 a spacecraft called Luna 2 was launched from Earth.
Luna 2 landed on the Moon.
i
ii
3.3 a
b
Describe how the weight of Luna 2 would compare between when it
was on Earth and when it was on the Moon.
[1]
Describe how the mass of Luna 2 would compare between when it
was on Earth and when it was on the Moon.
[1]
Explain what keeps the Earth in its orbit.
[2]
Explain why the planet Mercury travels faster in its orbit than Earth does.
[1]
3.4 The diagram shows the Earth and Moon. The diagram is not to scale.
a
b
c
Write the letter or letters where
there will be high tide on Earth
in this diagram.
[1]
A
D
There is also low tide at a place in
the diagram.
B
C
Earth
Moon
State the number of hours until the
next low tide in the same place.
[1]
Draw a diagram to show the positions of the Earth, Moon and Sun
that would produce the highest tides on Earth.
[1]
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3 Forces and energy
d
Use a word from the list to copy and complete the sentence.
[1]
gravity force mass energy
The Moon causes a tidal ……………….. on the Earth.
3.5 Which two measurements have the same units? Write the letter.
A
weight and mass
B
mass and energy
C
energy and force
D
weight and force
3.6 a
Which of these words means to spread out and become less useful?
[1]
[1]
thermal decrease dissipate loss
b
An electric motor works on electrical energy.
[2]
The motor changes electrical energy in three ways.
Write the energy in the correct columns.
useful
wasted
3.7 Which row in the table shows the forces on a planet in orbit around the Sun?
Put a tick (✓) in the box beside the correct row.
air resistance
gravity
no
no
no
yes
yes
no
yes
yes
[1]
3.8 A container of water is placed over a fire that burns wood.
a
Name the energy that is transferred from the fire to the water.
b
Not all of this energy is transferred to the water.
List two other places where this energy could go.accurate
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[1]
[2]
4
Grouping and
identifying organisms
4.1 Characteristics of
living organisms
In this topic you will:
•
think about what makes living organisms different from
non-living things
•
learn about the seven characteristics of living organisms.
Getting started
Key words
In your classroom, find one living thing and one thing that has
never been alive.
excretion
growth
movement
nutrition
organism
reproduction
respiration
sensitivity
With your partner, make a list of things that the living thing can
do, but the non-living thing cannot do.
Be ready to share your ideas with the rest of the class.
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4 Grouping and identifying organisms
Living and non-living
How do you know when something is alive? If it is a person, you can
check to see if they are breathing, or if they have a heartbeat.
Plants don’t breathe or have hearts, yet they are alive.
Living things are called organisms. Living organisms have a set of seven
characteristics that make them different from non-living things.
Nutrition: Plants feed by
photosynthesis. Bears eat meat.
Growth: All living
organisms grow.
Sensitivity: Living organisms
are sensitive to changes going
on around them.
Excretion: Living
organisms get rid of waste
materials, such as carbon
dioxide.
Movement: Living
organisms can move.
Reproduction:
Living organisms
can produce young.
Questions
These questions are about the picture of the polar bears. Copy and
complete the sentences.
Use these words. You can use each word once, more than once or not
at all.
carbon dioxide chewing
feeding growth movement
oxygen sight smell reproduce respiration
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Respiration: Food is
broken down inside
cells to provide energy.
4.1 Characteristics of living organisms
1
Another word for taking in nutrition is
2
Polar bears can sense things in their environment. For example, with
of meat.
their nose they can sense the
3
All living organisms excrete waste substances. Animals excrete
when they breathe out.
4
Living organisms
kind of organism.
5
Young plants and animals get bigger. This is called
…………………….. .
6
All living organisms break down some of the food they eat, to provide
them with energy. This happens in a process called ……………………… .
7
Most living organisms can change the shape and position of their
bodies. This is called ……………… .
.
to make more of the same
Activity 4.1.1
Is a car alive?
The picture shows a car.
Here are some facts about cars.
•
Cars use fuel and oxygen.
•
Inside the engine of the car, the
fuel and oxygen provide energy
to make the car move.
•
The engine produces waste gases,
including carbon dioxide.
These are given off in the exhaust of
the car.
•
Some cars have sensors. For example, they can sense when it is dark and turn the
lights on automatically.
Questions
1
In your group, make a list of similarities between a car and living organisms.
2
Make a list of differences between a car and living organisms.
Summary checklist
I can list the seven characteristics of living organisms.
I can describe the meaning of each of these characteristics.
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4 Grouping and identifying organisms
4.2 Viruses
In this topic you will:
•
learn about the structure of a virus
•
discuss whether viruses are non-living or living.
Getting started
Key words
Work with a partner to answer these questions.
electron
microscope
influenza
protein
replicate
RNA
virus
Respiration is one of the characteristics of living things.
List the other six characteristics.
Now explain the meaning of each of the words in your list.
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4.2 Viruses
What is a virus?
Viruses are very, very small. A virus is
much smaller than one of your cells.
You cannot see a virus with the kind of
microscope that you use in school.
To see a virus, you need to use a special
kind of microscope called an electron
microscope.
Viruses are not made of cells. They do not
have a cell membrane or cytoplasm. The
blue-green outer layer in the photograph
is a coat made of protein. There are little
pegs on the outside of this coat.
The orange part inside contains a
substance called RNA. The RNA is
made of little threads that contain a
set of coded instructions for making
more viruses.
This scientist is working in Jakarta, Indonesia. She is using an electron
microscope. The microscope is the grey object on the right-hand
side of the photograph. It produces a picture on the screen in front
of the scientist.
This photograph of viruses was taken by using an electron microscope. The viruses in the photograph look 100 000 times
bigger than they really are. It is almost impossible to imagine just how small a virus is.
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4 Grouping and identifying organisms
Think like a scientist
Making a model of a virus
You will need:
modelling clay, paper that you can tear into little pieces,
push pins
Use the materials to make:
•
an outer coat of protein
•
some little threads of RNA, inside the protein coat
•
some pegs on the outer coat.
You could take a photograph of your model, then stick the photograph into your
notebook.
How viruses replicate
Viruses cannot do anything at all on their own. They do not respire,
feed, excrete or grow. They are not sensitive and cannot move.
Viruses have to get inside a living cell before they
can make copies of themselves.
The brown viruses in the photograph are H3N2
influenza viruses. This kind of virus can
invade (get inside) cells of birds, humans
and other mammals. The viruses get
into your body by going up your nose
when you breathe in. The little pegs
on the virus’s coat help it to stick
onto one of your cells and then
get inside the cell.
When the viruses are inside the cell, each
virus bursts open. The virus forces the
cell to copy the instructions on its RNA,
and make many new viruses. This is called
replication. This kills the cell. Then the new
viruses burst out of the dying
cell, ready to infect more cells.
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4.2 Viruses
This makes the animal whose cells are infected feel ill. H3N2 viruses
cause a very unpleasant and dangerous kind of influenza (flu).
In 1968–1969, these viruses killed approximately one million people.
These flu viruses are just one of thousands of
different kinds of viruses we know about. Each kind
of virus has a particular kind of cell that it infects.
Some viruses infect plant cells.
In 2019, a new virus appeared. We do not know
exactly where it came from, but scientists think
it developed in a wild animal and then spread to
humans. The new virus is similar to the viruses that
cause flu and colds. Its official name is SARS-CoV-2.
The illness it causes is called Covid-19. This stands for
coronavirus disease 2019. The virus quickly spread all
over the world.
Many people get the virus without being ill at all,
or just have mild symptoms. But in some people,
it causes dangerous illness and even death.
Scientists will work hard for many years to find the
best ways of preventing this, including vaccination,
and drugs to treat Covid-19.
This is a drawing of a SARS-CoV-2 virus. The red bits
on the outside are called spike proteins. They help the
virus attach to cells and get inside.
Activity 4.2.1
Are viruses alive?
Some scientists consider that viruses are living organisms. Others
think that they are not.
In a group of three, discuss the question: Are viruses living
organisms?
Make a list of reasons for your decision. Be ready to share your
ideas with others.
Summary checklist
I can describe what a virus is and how it replicates.
I can give reasons for classifying viruses as living or non-living.
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4 Grouping and identifying organisms
4.3 What is a species?
In this topic you will:
•
look carefully for similarities and differences between
organisms
•
compare two different species of organism
•
find out how scientists decide if two organisms belong to the
same or different species.
Getting started
Key words
All living things belong to groups called species.
fertile
identical
infertile
offspring
species
specimen
variation
Imagine you are looking at two birds in your garden.
They look quite similar, but are not exactly the same.
Discuss this question with your partner: How would you
decide if the two birds belong to the same species or two
different species?
Be ready to share your ideas.
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4.3 What is a species?
Species
Scientists group living organisms into different kinds. Each kind of
organism is called a species.
Activity 4.3.1
Comparing two species of elephant
With a partner, look at the two pictures of elephants. These elephants belong to two
different species.
Make a list of the similarities that you can see between the two species of elephant.
Then make a list of differences that you can see between them.
Indian elephant
African elephant
Species and reproduction
All the organisms in a species share the same characteristics but they
are not all identical to each other. For example, some Indian elephants
have straighter tusks than others. They have pink markings on their
skin in different places. There is variation between the individual Indian
elephants.
Variation between individuals can sometimes make it difficult to decide
whether two organisms belong to the same species. To be sure, scientists
try to find out if they can reproduce with one another.
Indian elephants reproduce only with other Indian elephants. They do
not reproduce with African elephants. Each species reproduces only with
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4 Grouping and identifying organisms
other members of its own species. When they have offspring (children),
the offspring belong to the same species as their parents.
The offspring are fertile. This means they can also produce offspring.
Organisms that belong to different species cannot usually reproduce
with one another.
Very rarely, two organisms from different species do reproduce together.
This sometimes happens in a zoo. It can happen if two animals from
different species are put into the same enclosure.
For example, a male lion and female tiger in a zoo sometimes reproduce
together. They will only do this if they do not have a member of their
own species to reproduce with.
The young animals that are produced are called ligers. Ligers are healthy
animals. But ligers cannot reproduce. They cannot have offspring. They
are infertile.
So, we can describe a species as a group of organisms that can reproduce
together to produce fertile offspring.
A male lion (left) can breed with a female tiger (centre) to produce a liger (right).
Questions
1
Copy and complete these sentences.
Choose from these words.
bigger
different
identical
similar
Organisms that belong to the same species usually look
to one another.
They look
from organisms belonging to other species.
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4.3 What is a species?
2
Explain why biologists say that lions and tigers belong to different
species, even though they can sometimes reproduce together.
Think like a scientist
Comparing organisms belonging to different species
This task will give you practice in looking very carefully at specimens (samples) of
organisms. You will also practise describing similarities and differences.
You will need:
• specimens of two similar species of organism
Safety
If you handle live organisms, wash your hands carefully afterwards.
Look carefully at the specimens. The organisms belong to two different species.
Questions
1
Write down five similarities between the two species.
2
Now write down some differences between them. Try to find at least two differences.
3
Suggest what a scientist would do to be sure that these organisms really do belong to
two different species.
Summary checklist
I can compare organisms belonging to different species.
I can describe what is meant by the word ‘species’.
I can explain how scientists decide whether organisms belong to
the same species.
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4 Grouping and identifying organisms
4.4 Using keys
In this topic you will:
•
learn how to use a key to identify an organism, or to classify it
into a group
•
change a key from one style to a different style.
Getting started
Key words
Discuss this question with a partner.
dichotomous
key
Imagine you have found an insect that you have never seen
before. You want to know what its name is.
How would you try to find out? Try to think of at least three
ways in which you could do this. Which way do you think would
be the best?
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4.4 Using keys
Identifying organisms
Biologists often want to identify an organism that they have found.
A good way to start is to look at pictures in a reference book, or on the
internet. The biologist may be able to find a picture of the organism,
with its name. But this does not always work.
Biologists also use keys
to help them to identify
organisms. A key is a set of
questions about the organism
you want to identify. The
answer to each question
takes you to another question.
You work through all of the
questions until you arrive at the
name of the organism.
Here is a simple key to help
someone to identify an organism.
It is a dichotomous key.
Dichotomous means ‘branching
into two’.
You will have to imagine that you
have the whole animal to look at,
not just these pictures.
To use the key:
•
Choose one organism
you want to identify.
•
Starting at the top of
the key, answer the first
question – yes or no?
•
Follow the line to the
next question. Keep
going until you arrive
at the name of the
organism.
Does it have legs?
Yes
No
Does it have more than six legs?
Is its body made up of rings?
Yes
No
Yes
No
crab
Does it have four wings?
earthworm
slug
Yes
No
dragonfly
housefly
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4 Grouping and identifying organisms
Keys are sometimes arranged differently. Here is the same key set out
in a different way.
Instead of a question, the key starts with a pair of statements to
choose from.
Instead of arrows pointing to where you go next, there is a number
telling you which pair of statements to go to next.
1
2
3
4
a
It has legs.
go to 2
b
It does not have legs.
go to 3
a
It has exactly six legs.
go to 4
b
It has more than six legs.
crab
a
Its body is made up of rings.
earthworm
b
Its body is not made up of rings.
slug
a
It has four wings.
dragonfly
b
It has two wings.
housefly
Try working through the key to identify the dragonfly.
You will work through steps 1a, 2a, 4a.
Questions
1
Using the key above, which steps would you go through to identify
the earthworm?
2
Explain why the key is called a dichotomous key.
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4.4 Using keys
Think like a scientist
Using a key to identify species of fish
The pictures show four species of fish.
A
B
C
D
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4 Grouping and identifying organisms
Continued
Questions
1
Use this key to identify the four species of fish.
Remember:
•
Take one fish at a time. Start with fish A.
•
Start at the top of the key and work your way through the questions and answers
until you arrive at the name of the fish.
•
Then do the same for fish B, and so on.
Does it have stripes?
2
Yes
No
Are the stripes vertical?
horn shark
Yes
No
Do the fins have spines?
zebra fish
Yes
No
dragon fish
clown fish
Here is the beginning of the same key, written out in the style that uses pairs of
statements for you to choose between.
1
a The fish has stripes. …………………….. go to 2
b
The fish does not have stripes. …….…… horn shark
Write out the whole of the key in this style.
Which style of key do you find easier to use? Why do you think
it is easier?
Summary checklist
I can use a dichotomous key to identify an organism.
I can write a key in a different style.
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4.5 Constructing keys
4.5 Constructing keys
In this topic you will:
•
learn how to create your own key
•
learn how to change your key following feedback.
Getting started
Here are four questions that could be part of a dichotomous
key to identify some different plants.
•
Is the plant tall?
•
Do the flowers on the plant have five or more petals?
•
Does the plant have dark green leaves?
•
Are the leaves darker on the upper surface than on the
lower surface?
With a partner, think about these four questions.
Which two questions would not be good to use in a key?
Explain your answer.
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4 Grouping and identifying organisms
Constructing a key
Look at the photographs of four learners.
Imagine you are going to construct a key to help someone to identify
these learners.
Step 1
Think of a way you can split the learners into two groups. For
example, you could split them into male and female learners.
So, your first question could be: Is the learner female?
Step 2
Deidre
Now look at just one of these groups – the female learners, for
example. Think of a way to split these into two. For example, you
could use the colour of their hair.
Step 3
Repeat Step 2 until you have thought of ways to identify each
learner in turn.
Now use your ideas to complete the ‘Think like a scientist’ activity.
Ben
Elsa
Ari
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4.5 Constructing keys
Think like a scientist
Making keys to identify four learners
1
Copy this key and complete it, to help someone to identify each of the four learners in
the photographs.
Is the learner male?
Yes
2
No
Yes
No
Yes
No
Ben
Ari
Deirdre
Elsa
Now try writing your key in the other style, using pairs of statements, 1a and b, 2a and
b and so on.
You could use the same pairs of features as for your first key, or you could challenge
yourself to use different pairs.
Peer assessment
Exchange your key with a partner.
For each of the four statements below, give your partner:
2 marks if they did it really well
1 mark if they have done it quite well
0 marks if they have done it very badly, or not at all
•
They have written a key that is made up of pairs of statements to choose from.
•
It is easy to choose between the statements each time.
•
There are no more than three pairs of statements to choose from.
•
The key works – someone can use it to identify the four learners.
With your partner, look at the marks you have given each other.
What could each of you do better next time?
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4 Grouping and identifying organisms
Think like a scientist
Writing a key to identify species of cat
The photos show four different species of cat.
Pallas’s cat
Leopard
Lynx
Tiger
1
Write a key that someone can use to identify these four cat species.
You can use either style of key.
2
Exchange your key with a partner and ask them to try it out. Does it work?
Ask them for suggestions for improving it. Use their ideas to make
some changes to your key so that it works better.
What problems did you have writing your key? How did you
solve them?
Summary checklist
I can write my own key.
I can use feedback from a user to improve my key.
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4.5 Constructing keys
Project: Consequences of classifying organisms
In this project, you will work in a group to think about how different decisions about
classifying organisms can affect their chances of survival. You will produce a short play to
show some of the viewpoints of people who may be affected by these decisions.
Biologists often disagree about whether two kinds of organism should be classified as the
same species or as different species. This can cause arguments about whether to try to
save a particular kind of organism, or to protect a habitat.
Imagine there is a small area of rainforest where farmers want to plant coffee trees.
Coffee traders want to build a factory to process and pack coffee beans, to sell.
Some biologists say that there are 200 different species of birds that live in this forest.
If the forest is cut down, some of these species may become extinct. But other biologists
disagree. They say that 100 of these ‘species’ are not different species at all.
In your group, plan and act a short scene involving these people:
I am sure there
are at least 200 different
species of bird here.
It was noted at an earlier proof
stage that these artworks are very
Primary level. They need to be
redrawn.
If we build a coffee
packing factory here, we
can employ a lot of
people.
Tech-Set:
I think a lot of your
species are not different species
at all; but certainly there are at
least 100 different species of
bird in the forest.
If I can plant coffee
trees here, I can make a
lot of money.
If you wish, you could include other people, such as children who like to play
in the forest, or someone from an international conservation organisation.
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4 Grouping and identifying organisms
Check your Progress
4.1 The list describes some of the features of a horse.
•
It can move.
•
It has a heart.
•
It has hair.
•
It feeds.
•
It respires.
•
It can sense changes in its environment.
•
It has a brain.
a
Write down each feature in the list that is a characteristic of all living things.
[4]
b
Write down two more characteristics of living things that are not included in
part a.
[2]
4.2 The pictures show some animals that belong to different groups.
A
B
C
D
E
Use the key to classify each animal into the correct class.
1
2
3
a
has three pairs of legs……………………………………… class insects
b
has more than three pairs of legs……………………… go to 2
a
ody has many segments (rings) with a pair
b
of legs on each segment………………………………… class myriapods
b
does not have a pair of legs on each segment………… go to 3
a
has eight legs……………………………………………… class arachnids
b
has more than eight legs………………………………… class crustacea
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[5]
4 Grouping and identifying organisms
4.3 A scientist studies birds in New Zealand. The photographs show two kinds of parakeet
that live there.
The scientist wants to find out if these two kinds of parakeet belong to different species.
Yellow-crowned parakeet
Red-crowned parakeet
She searches in suitable habitats for pairs of parakeets that are making nests.
She never finds a yellow-crowned parakeet that has paired up with a red-crowned
parakeet.
a
The scientist concludes that the yellow-crowned parakeet and red-crowned
parakeet belong to two different species.
What evidence does she have for making this conclusion?
b
[2]
Suggest what the scientist should do to be even more certain that her
conclusion is correct. Choose from:
•
looking at stuffed specimens of parakeets in a museum
•
checking more pairs of parakeets in the wild
•
looking at other species of parakeets.
[2]
Explain your answer.
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4 Grouping and identifying organisms
4.4 The photograph shows six flowers, A to F.
A
is Limnanthes
D is Lunaria
B
is Viola
E
is Erodium
C
is Potentilla
F
is Silene
B
A
D
C
E
F
Here is part of a key that someone could use to identify each of the flowers.
[4]
Copy and complete the key.
1
a
The flower has exactly four petals. …………………… Lunaria
b
The flower has more than four petals. ……………….. go to 2
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5.1 Metals and non-metals
5
Properties of
materials
5.1 Metals and non-metals
In this topic you will:
•
list the properties of metals and non-metals
•
learn about the uses of metals and non-metals.
Getting started
Key words
Look around the room you are in. Can you identify at least five
different metals?
brittle
conduct
ductile
insulators
magnetic
malleable
materials
shatter
shiny
sonorous
How do you know that they are metals?
Compare your ideas with a partner.
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5 Properties of materials
Metals
Metals are very useful materials. Materials are the
substances from which objects are made.
There are many different metals. Metals are used to do
different jobs.
Metals are strong and tough. They do not shatter when
dropped and they do not crack easily. They can hold large
weights without breaking.
Iron is used for bridges because it
is strong.
Metals are shiny when they are freshly cut or polished.
Author needs to provide an
additional reason why gold is
used to make jewellery. 'Because
it's shiny…' is a bit lame.
Tech-Set: no comment within
query log. Please advise
Gold is used for jewellery because it
is shiny.
Metals can be bent to shape them. Metals are malleable,
which means they can be hammered into shape.
Iron is malleable.
Metals are ductile, which means that they can be drawn out
into wires.
Copper is ductile.
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5.1 Metals and non-metals
Metals make a ringing sound like a bell when they are hit;
the word for this is sonorous.
Cymbals make a ringing sound when hit.
Most metals do not melt easily. They have high melting
points and high boiling points. Mercury is the only metal
that is liquid at room temperature.
A lot of heat is needed to melt metal.
Metals are good conductors of heat. When you touch
them they conduct heat energy away from the hand so they
feel cold.
Steel conducts heat well, which is useful
for cooking pans.
Some metals are magnetic. Iron, steel, nickel and cobalt
are magnetic.
Some metals are magnetic.
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5 Properties of materials
Metals are good conductors of electricity.
This means that an electric current can
flow through them.
You need to remember that:
•
the surface of most metals will become
dull after a while
•
big lumps of metal are hard to test
for flexibility
•
bottles and cups also make a ‘ringing’
sound when they are hit, but they
are not made of metal.
Copper is used for electrical wiring because it conducts electricity
well and is flexible.
Questions
1
List ten metals.
2
Why are gold and silver used for jewellery?
3
Why is copper so useful?
4
What do ‘malleable’ and ‘ductile’ mean?
5
What are Olympic medals made from?
6
Where are metals found in the Periodic Table?
Think like a scientist
Properties of materials
In this task you will investigate metal items such as electrical wire, scissors and a hammer.
1
Describe each item.
2
If you know what it is made from, name the metal. If you don’t know, try to find out.
3
Suggest which property of the metal is important in the function of this item.
4
Make a table of your results like this:
Item
Metal
Useful property
Electrical wire
Copper
It conducts electricity. It is ductile.
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5.1 Metals and non-metals
Non-metals
Non-metals are often very useful because of the chemical
reactions they have with other substances. There is a lot of
variation between non-metals.
Properties shared by almost
all non-metals
Non-metals look dull. They do not reflect light very well and
the surface is not as smooth as metals.
Sulfur is added to rubber to make
it hard.
Non-metals that are solids are brittle. If you drop them they
may shatter.
Most non-metals do not conduct heat energy well. This is very
useful because some of them can be used to make handles for
cooking pans, for example.
Most non-metals do not conduct electricity. This is very useful
because some can be used to make coverings for electric plugs
and cables, for example. They are known as insulators; this
means they do not conduct heat or electricity.
Pure oxygen is used in hospitals for
people with breathing difficulties.
Properties shared by many non-metals
Non-metals are not as hardwearing as metals.
Many non-metals are gases.
The non-metals that are not gases have low melting points
and low boiling points.
These balloons are filled with helium.
Chlorine is used to kill bacteria. For
example, it can be dissolved in water
and then added to swimming pools.
Carbon is used to purify water and to
treat indigestion.
Silicon is used to make computer chips.
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5 Properties of materials
Questions
7
Name five non-metals, other than sulfur and helium.
8
What is sulfur used for?
9
What property of helium makes it useful in balloons?
10 Where would you find the non-metals in the Periodic Table?
Summary checklist
I can recognise the properties of metals and non-metals.
I can identify the useful properties of metals and non-metals for a
particular function.
I can name ten metals and five non-metals.
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5.2 Comparing metals and non-metals
5.2 Comparing metals
and non-metals
In this topic you will:
•
compare the properties of metals and non-metals
•
investigate materials and decide if they are metals or
non-metals.
Getting started
Key words
What do the terms ‘ductile’, ‘sonorous’, ‘malleable’ and
‘brittle’ mean?
contact
distinguish
examine
Draw cartoon diagrams to help you explain their meanings.
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5 Properties of materials
Comparing metals and non-metals
Metals and non-metals have different properties.
Metals
Non-metals
• Most are solid at room temperature.
• Many are gases at room temperature.
• They are shiny.
• They are dull.
• They do not shatter.
• They are brittle.
• They conduct heat energy well.
• They do not conduct heat energy well.
• They conduct electricity.
• Most do not conduct electricity.
• They are malleable.
• They are ductile.
• They are sonorous.
Look carefully at this photograph of a market scene. What do you see?
Questions
1
List five objects in the photograph of a market that are made of
metal and five that are made of non-metals.
2
A material is dull, brittle and does not conduct electricity. Is it a
metal or non-metal?
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5.2 Comparing metals and non-metals
3
Mercury is a metal. What unusual property does it have?
4
Write down two things that a metal can do better than a non-metal.
Think like a scientist
Investigating materials
In this task, you will be given a number of different materials to investigate. You will
examine each material closely and test it so that you can distinguish (identify) which are
metals and which are non-metals.
You will need:
a selection of materials to test, electrical wires,
a lamp, a cell (battery), crocodile clips
1
2
Ask a number of questions for each of the materials you investigate.
•
What does the material look like? Is it shiny or dull?
•
Does it make a ringing sound when you hit it?
•
Is it brittle?
•
Can you bend it?
•
Does it feel hot or cold?
•
Does it conduct electricity?
cell
To test if the material conducts electricity, you
can set up a circuit as shown in the diagram.
Before you start, check that the lamp is
working by connecting the crocodile clips
together with no test materials. When
you carry out the test make sure you have
good contact between the crocodile clips
and your test material.
lamp
clips
Testing a material to see if it conducts electricity.
Question
1
Draw a table for your results. Decide if each material is a metal or and non-metal.
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5 Properties of materials
1
Were any of the materials difficult to place in the
metals or non-metals group? Explain your answer.
2
Which do you think was the most useful test to
distinguish between metals and non-metals?
Activity 5.2.1
Researching metals and non-metals
Choose one metal and one non-metal. Use reference books
and the internet to find out about each of them.
Here are some useful questions you could research.
•
What is the metal or non-metal used for?
•
What are its properties?
•
How are these properties useful?
•
Where is it found?
•
Does the metal or non-metal need to be processed before
it can be used? If so, how is this done?
•
Are there any other interesting facts about it?
Present your research as reports or posters.
Write a paragraph comparing your metal and non-metal.
Useful words and phrases might include ‘whereas’, ‘lighter than’,
‘higher melting point than’, ‘compared with’. Make sure you
actually compare the two and do not just list the two sets of
properties. For example: Metals have shiny surfaces whereas
non-metals have dull surfaces.
Summary checklist
I can distinguish between metals and non-metals.
I can carry out investigations to distinguish between metals and
non-metals.
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5.3 Metal mixtures
5.3 Metal mixtures
In this topic you will:
•
learn about metal mixtures (alloys)
•
use particle theory to explain the differences in the properties
of metals and their alloys.
Getting started
Key words
Look at the diagrams below. Are they elements, compounds or
mixtures? Give reasons for your answers.
alloy
bronze
disrupt
steel
A
B
C
D
SEE QUERY LOG
This is a repeat of question 2.7 in
Check your progress on page 66.
One of them should be replaced.
The item here is a repeat of 2.7 in
Check your progress on page 66,
one of which should be replaced.
Tech-Set: no comment within
query log. Please advise
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5 Properties of materials
Alloys
Metal mixtures are called alloys. Alloys are made by mixing different
metals together and melting them. The atoms of the different metals mix
but do not bond together. The properties of the alloys are different from
the metals they contain.
Bronze is an alloy made by mixing copper and tin. Bronze is harder than
either copper or tin.
People learnt to melt copper and tin together to make bronze a very long time ago. This
bronze head (left) was made in what is now Iraq, more than 4000 years ago. The statue on
the right was made in Greece, about 2500 years ago
Steel is an alloy, but an unusual one because one of the elements in the
mixture is not a metal. Steel is a mixture of iron and carbon. Pure iron
is not hard enough to be very useful but when it is mixed with other
elements to form steel it is much harder.
Sometimes, chromium and nickel are also added to steel. This type of
steel does not rust and is used for cutlery.
The reasons why the alloys have different properties from the pure metal
is to do with the arrangement of the particles of the elements. In a pure
metal, the atoms are all the same size and arranged in regular rows. The
layers can slide over one another easily. This is what happens when the
metal is hit with a hammer. What do we call this property? This also
happens when the metal is stretched out. What do we call this property?
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5.3 Metal mixtures
force
When a force is applied, layers slide over one another easily in a pure metal.
force
a different sized atom
disrupts the regular pattern
the atoms cannot slip past one
another easily now.
An alloy. The layers of atoms can’t slide over each other as easily now. They get stuck in place.
This makes the alloy a lot harder and stronger than the original metal.
Think like a scientist
Modelling a metal and an alloy
You will need:
The apparatus as shown in diagram.
1
2
syringe
diluted washing
up liquid
Make rows of small bubbles in the dish, as
shown in the diagram. Push the syringe plunger
in slowly and steadily to make sure the bubbles
are all the same size. The bubbles represent
the atoms in a metal.
Fill the dish with bubbles to model the close
packed arrangement of atoms.
Petri dish
a bubble raft
A Petri dish containing diluted washing
up liquid.
Questions
1
Do the bubbles line up in rows?
2
What happens when a bubble bursts?
3
Can you see how easily the rows of bubbles slide past each other?
Describe what you see.
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5 Properties of materials
Continued
Inject a larger bubble into the middle of the dish. You do this by pushing harder and for
longer. You may have to have several goes to achieve it – it takes a bit of practice.
This is like adding an atom of a different metal. You now have a model of an alloy.
4
Can you see how this disrupts the regular pattern of bubbles? Describe what you see.
How good a model of the particle arrangement in an alloy was
this? How well did it help you to understand the idea?
Alloys in everyday life
Coins
The coins in your pockets are made from alloys. Pure metals
are too soft to withstand all the wear they get. The coins that
look silver are not made of silver – it is too soft and far too
expensive. The silver coins are made of alloys containing
copper and nickel. The copper coins contain copper, zinc
and tin. Coins must be hardwearing but also malleable enough
to be stamped with complex patterns.
Jewellery
Most gold jewellery is not pure gold; it is an alloy of gold and
copper. Pure gold is soft. If you used pure gold for something
like a wedding ring (that gets a lot of wear and tear) it would
wear away. A wedding ring should be made from something
stronger. Pure gold is 24 carat: that means that 24 parts out of
24 are gold. 18 carat gold has 18 parts out of 24 of pure gold,
and six parts of other metals such as copper, silver or zinc.
Aeroplanes
The metal used to build planes needs to be light but very
strong. Planes are mainly made of aluminium, but pure
aluminium would not be strong enough and the plane’s wings
would fall off because of the great stress put on them during
flight. By adding magnesium and copper, an alloy called
duralumin is formed. Duralumin is about five times stronger
than pure aluminium.
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5.3 Metal mixtures
Artificial joints
The joints in our bodies take a lot of wear and tear. Sometimes, the
joints are attacked by arthritis. This is a very painful and crippling
disease. Now people can be fitted with replacement joints. These are
made of plastic and alloys, often alloys of titanium.
X-ray of the pelvis showing a hip replacement.
Titanium hip joint
Modern alloys
Modern alloys have been developed that have
some very useful properties. Some glasses f
rames are made of shape memory alloy. This
alloy is called Nitinol. Nitinol is made of
nickel and titanium.
SEE QUERY LOG
No information is given about properties
(returning to its original shape when heated), but
knowledge is needed to answer Q9 on page 159.
No information is given about the properties of
shape memory alloys in the LB text, but question
9 on p159 expects some knowledge of these.
Tech-Set: no comment within query log. Please
advise
Questions
1
What is an alloy?
2
Which properties of aluminium make it
useful for building planes?
3
Why is an alloy of aluminium used for
making planes instead of pure aluminium?
4
Pure gold is 24 carat gold. What does this mean?
5
Explain the difference between the purity of 18 carat gold and 24 carat gold.
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5 Properties of materials
6
Why do we not use pure silver for our coins?
7
Why do we use pure copper for our coins?
8
What properties must an alloy used inside the body have?
9
Why are some glasses frames made from shape memory alloy?
Brass and bronze
Brass is an alloy of copper and zinc. There are different types of brass,
made by using different amounts of copper and zinc. Sometimes, other
elements such as lead, aluminium, manganese or silicon are added.
Look at the table of information about copper, zinc and brass.
Name
Copper
Zinc
Brass
Element or
mixture?
element
element
mixture
Appearance
reddish brown soft
metal
silvery grey soft metal
golden yellow, reddish
gold or silver soft alloy
Melting point
1085 °C
419.5 °C
900−1000 °C
Properties
very ductile and
malleable
less ductile and
malleable than copper
less ductile than
copper; more
malleable than zinc and
copper
conducts heat and
electricity well
conducts heat and
electricity less well than
copper
conducts heat and
electricity less well than
zinc
resistant to corrosion
Example uses electrical wiring; central to cover iron in a thin
heating pipes
layer to prevent it from
rusting
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musical instruments,
plumbing
5.3 Metal mixtures
Look at the melting points: copper and zinc have just one temperature
listed. However, brass has a range of temperatures. There are
many different types of brass, which are made by using different
amounts of copper and zinc. So, there is no specific melting point for
brass; it depends on the proportions of copper and zinc that have been
used.
Another alloy of copper is bronze. Bronze is an alloy that is made by
mixing copper with tin. Sometimes, other elements such as manganese,
phosphorous, aluminium or silicon are added. Mixing different amounts
of copper and tin makes the different forms of bronze. Each different
mixture has its own different melting point.
Name
Copper
Tin
Bronze
Element or
mixture?
element
element
mixture
Appearance
reddish brown soft
metal
white metal
reddish brown not as
bright as brass
Melting point
1085 °C
232 °C
860 −1150 °C
Properties
very ductile and
malleable
soft, ductile and
malleable
less ductile than
copper; hard; brittle
conducts heat and
electricity well
conducts electricity
less well than copper
good conductor of
electricity
does not corrode
readily
corrosion resistant
coating the inside of
food cans and in many
different alloys
bronze sculptures;
bells and cymbals; ship
fittings (especially parts
which are submerged
under water); electrical
connectors
Example uses
electrical wiring;
central heating pipes
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5 Properties of materials
Questions
10 Why is a range of temperatures given for the melting point
of bronze?
11 Give one property that brass and bronze share.
12 Give one property that copper and zinc share.
13 Give one difference in properties between copper and tin.
Summary checklist
I can describe some alloys and their uses.
I can explain that alloys have different properties from the metals
they are made from.
I can explain the differences in the hardness of metals
and their alloys using particle theory.
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5.4 Using the properties of materials to separate mixtures
5.4 Using the properties
of materials to separate
mixtures
In this topic you will:
•
use what you know about mixtures to separate them
•
choose apparatus to carry out a practical task
•
carry out practical work in a safe way.
Getting started
Key words
1
What is the difference between a mixture and a compound?
Discuss it with a partner.
2
How could you separate a mixture of dry rice and peas?
Discuss your ideas with a partner and be prepared to share
them with the class.
condenser
conical flask
filter funnel
filter paper
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5 Properties of materials
Making mixtures
Mixtures contain different substances that are not combined together
chemically. You made a mixture with iron filings and sulfur in topic 2.7.
You separated the iron and sulfur in your mixture by using a magnet.
You used the difference in the properties of iron and sulfur to separate
them. Iron is magnetic; sulfur is not magnetic.
Separating mixtures
Copper sulfate and water
The evaporating dish contains a mixture of water and copper sulfate.
If it is left in a warm room, the water evaporates and leaves the copper
sulfate behind in the dish.
Food dye and water
A mixture of food dye and water can be separated by using a piece
of apparatus called a condenser. It is used to separate mixtures of
two liquids.
The water and food dye mixture is heated and boils. The liquid water
reaches the temperature where it changes state and becomes a gas.
Water that is in the gas state is called steam when it has been formed by
boiling the water. The gas travels along the tube into the condenser. The
cold water that is circulating around the outside of the condenser cools the
gas down. This makes the gas condense back into liquid water. The liquid
water collects in the beaker. The food dye remains in the heated container.
The water evaporates and
leaves the copper sulfate in
the evaporating dish.
The food dye and water have different properties that allow you to
separate them – they have different boiling points.
water out
the steam cools and
condenses as water
100 °C
the water in the red solution
evaporates as steam
condenser
mixture of water
and red food dye
cold water in
heat
pure water
Separating water from a mixture of food dye and water.
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5.4 Using the properties of materials to separate mixtures
Questions
1
Explain how the water in the flask changes to a gas.
2
Explain how the steam changes back into a liquid in the condenser.
3
Which different properties of the water and the food dye are used
to separate them?
Think like a scientist
Separating sandy, salty water
Your task is to separate a mixture of sandy and salty water.
You will need:
The apparatus shown in the diagrams.
clear
liquid
beaker
filter funnel
sandy,
salty water
safety
glasses
filter paper
tongs
evaporating
dish
clay pipe
triangle
conical flask
tripod
clear liquid
bunsen
burner
1
Prepare a filter paper and place it in a filter funnel. Place the funnel in the conical flask.
2
Pour the mixture into the funnel. Take care to add it slowly so that the mixture does not go
down the outside of the filter paper. Do not disturb the wet filter paper because it tears easily.
3
When you have filtered all the mixture, leave the filter paper in a warm place to dry.
4
Place the clear liquid from the conical flask in an evaporating basin. Wear safety
glasses. Heat this gently. When the liquid starts to spit, remove it from the heat.
5
Leave the liquid in a warm place to evaporate.
Questions
1
Suggest why the sand remains in the filter paper.
2
One group of students thought their mixture was taking too long to filter so they used
a pencil to stir it up while it was in the filter paper. Explain why this is not a good idea.
3
What safety precautions should you take when heating the salty water?
4
How could you obtain the water from your mixture?
5
The salt left in the evaporating basin is a little dirty. Suggest what you could do to get
cleaner salt.
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5 Properties of materials
How carefully did you carry out this practical task? How well did
you consider safety? How could you improve the way you carry out
a practical next time you do one?
Think like a scientist
Separating two solids
If you mix powdered black carbon and table
salt together you have a mixture of two solids.
How can you separate the carbon from the salt?
What do you know about the properties of
carbon powder and table salt that might be
useful here?
Make a plan of how you could do this.
Remember to think about safety.
Make a list of the equipment you would need.
black carbon
beaker
salt
Making a mixture of powdered carbon and table salt.
Discuss it in your group.
Share your ideas with the class.
Did you change any of your ideas when you discussed them with the class?
Carry out your plan, once it has been checked for safety.
Questions
1
Which properties of the two solids did you decide to use to help separate them?
2
Write down your final list of the equipment you will need.
3
Write an outline of your final plan. Explain how the steps will enable you to separate
the two solids. Draw diagrams if that helps to make your plan more clear.
4
What safety precautions should you take?
Self-assessment
How successful were you in separating the two solids? How could you improve your results?
Summary checklist
I can identify properties of different substances in a mixture and use
those to separate them.
I can choose appropriate equipment for a practical task.
I can carry out a practical task safely.
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5.5 Acids and alkalis
5.5 Acids and alkalis
In this topic you will:
•
learn about the properties of acids and alkalis
•
learn how to work safely with acids and alkalis
•
find out about hazard symbols.
Getting started
Key words
What do you think of when you hear the word ‘acid’? Write
down five words that describe what you think an acid is. Share
these with a partner. Did you both come up with same or similar
words? Be prepared to share them with the class.
acid
alkalis
corrosive
flammable
harmful
irritate
oxidising
toxic
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5 Properties of materials
Acids are everywhere
Many things contain acid. Some foods contain acid. These foods have a
sour, sharp tangy taste. Lemons and limes taste sour. They contain citric
acid. This is a weak acid.
Common acids in the laboratory are hydrochloric acid, sulfuric acid and
nitric acid.
Foods containing fruits often contain acids.
Some acids are dangerous
Some acids are strong. They are corrosive. The bottles have
a hazard warning label. If strong acid gets onto your skin,
it will dissolve the skin. You will get a chemical burn.
Always use eye protection when using acids.
Acids can be diluted with water. This makes them
less dangerous.
Dilute acids are still harmful, they can irritate your skin and
eyes. The bottles have hazard warning labels.
If you spill acid, wash the area with lots of water. The water
dilutes the acid.
Questions
1
Name a food that contains acid.
2
Describe the taste of lemons and limes.
3
What does corrosive mean?
4
What should you do if you spill acid?
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dilute
Sulfuric Acid
hydrochloric
Acid
dilute
Nitric Acid
5.5 Acids and alkalis
Alkalis are everywhere
Many cleaning products contain alkalis such as sodium hydroxide, which
is a compound of sodium, hydrogen and oxygen. Sodium hydroxide is a
strong alkali. Strong alkalis are dangerous. They are corrosive.
If strong alkali gets on your skin, it dissolves your skin. Your skin feels
soapy. You get a chemical burn. Alkalis are harmful if you get them in
your eyes. Always wear eye protection when using alkalis.
Alkalis can be diluted with water. This makes them less dangerous.
Common alkalis found in the laboratory are sodium hydroxide,
potassium hydroxide and calcium hydroxide.
Acids and alkalis are chemical opposites. They cancel each other out
when they are mixed together. The acidity or alkalinity of a substance is
a chemical property of that substance.
sodium
hydroxide
All these products contain alkalis.
Strong sodium hydroxide is corrosive.
Working safely with acids and alkalis
When you handle chemicals you should:
•
stand up to work, so that if you spill something it does not spill on
to you
•
wear safety glasses, so nothing gets into your eyes
•
take the top of the bottle and place it upside down on the work surface,
so that it does not get acid onto the surface or dirt into the acid
•
replace the bottle top as soon as you have finished using the bottle.
This prevents spills and reduces the risk of replacing the wrong top
on the wrong bottle.
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5 Properties of materials
Hazard warning labels
Many chemicals are hazardous. Their bottles are clearly labelled with
hazard warning symbols so that you know you must handle them
carefully. Here is a list of the most common hazard symbols and what
they mean.
Explosive
A substance that
can explode if it
comes into contact
with a flame or
heat.
Flammable
A substance that
can catch fire
easily.
Oxidising
A substance
that gives off a
large amount
of heat when in
contact with other
substances.
Corrosive
A substance that
can destroy living
tissue. It can cause
burns.
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5.5 Acids and alkalis
Toxic
A substance that
can poison you.
Hazardous to the
environment
A substance that
can kill or damage
living things in the
environment.
Health hazard
A substance that
can cause harm
such as irritating
your skin and eyes.
Serious health
hazard
A substance that
can cause a serious
problem to your
health.
When you use chemicals in the laboratory, make sure you look at the
hazard symbols and listen to advice on how to use them safely.
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5 Properties of materials
Activity 5.5.1
Learning the hazard warning symbols.
You will need:
•
card
•
scissors
Make three sets of cards:
•
one set with the hazard warning symbols on them
•
one set with the names of the hazards on them
•
one set with the details on them.
You must make up a game with these cards to help you
learn the symbols and their meanings.
Play your game with a partner, and then play their game.
Peer-assessment
Was your partner’s game useful to help you learn the symbols? How could they improve
their game? How did your game compare?
Which methods of learning information like this are the most
helpful to you?
Summary checklist
I can identify the properties of acids and alkalis.
I can explain how to work safely with acids and alkalis.
I can identify and understand the hazard warning symbols.
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5.6 Indicators and the pH scale
5.6 Indicators and the
pH scale
In this topic you will:
•
learn how to tell an acid from an alkali
•
learn how to make and use indicators
•
use the pH scale to find out more about acids and alkalis.
Getting started
Key words
Draw one of the hazard warning symbols. Show it to your partner.
Can they identify it? Test each other on as many as you can
remember. Check up and see how many you got correct and how
many you forgot.
indicator
litmus
neutral
pH scale
universal
indicator
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5 Properties of materials
Which is which?
These three containers all look the same. One contains water, one
contains acid and one contains alkali.
You can tell them apart when you add a few drops of an indicator. An
indicator turns one colour in an acid and a different colour in an alkali.
Red cabbage juice can be used as an indicator.
red cabbage
juice
Red cabbage indicator turns acids red in acids, blue in water and yellow
in alkalis.. So, you now know what was in each beaker.
hydrochloric acid
water
sodium hydroxide
Indicators can be made from the brightly coloured berries, flowers and
other parts of plants. These include:
•
red cabbage
•
blackcurrant
•
beetroot.
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5.6 Indicators and the pH scale
Questions
1
How does an indicator show whether a substance is an acid or
an alkali?
2
What is the colour change when red cabbage juice is added to
lemon juice?
Litmus
Litmus is a very common indicator. It is a dye. You usually use litmus
paper, which is made by soaking absorbent paper in litmus solution.
Litmus turns red in acids. Litmus turns blue in alkalis. Litmus turns
purple when it is in a neutral substance. A neutral substance is one that
is neither acid nor alkali.
Litmus turns purple in water. Water is neutral. This means water is
neither an acid nor an alkali.
This table shows the colours litmus goes in some substances and what
those colours mean.
Substance
Litmus colour
Type of substance
hydrochloric acid
red
acid
sodium hydroxide
blue
alkali
water
purple
neutral
lemon juice
red
acid
calcium hydroxide
blue
alkali
Questions
3
What does litmus do when it is added to sodium hydroxide?
4
What colour does litmus change to in an acid?
5
Is water an acid, an alkali or neutral? Give the reason for your
answer.
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5 Properties of materials
Think like a scientist
Making and using your own indicator solution
In this task you will make your own indicator solution and use it to test various chemicals
in the laboratory.
You will need:
some plant material, such as red cabbage or beetroot,
a knife and cutting board, a pestle and mortar, two dropper
pipettes, test tubes and a test-tube rack, safety glasses,
a range of laboratory chemicals, ethanol
Safety
Make sure you are careful and read all
the hazard warning labels. Ethanol is
flammable.
1
Cut up the plant material.
2
Place some of the material into a pestle
and mortar and crush it.
3
Use a pipette to add a little ethanol.
4
Crush the plant material again.
5
Use a different pipette to transfer some
of the liquid from the mortar to a test
tube.
6
Use the liquid you collect to test
some everyday liquids and laboratory
chemicals.
7
Make a table to record the chemicals
you test and the colours you see.
plant pieces
pestle
pipette
ethanol
motar
Crush the plant pieces.
Add a little ethanol.
pipette
Keep crushing until
the colour comes out.
Use a pipette to put the
liquid into a test tube.
Self-assessment
Compare your indicator with litmus. Does your indicator turn the same colour as litmus?
Does it clearly show which is an acid and which is an alkali?
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5.6 Indicators and the pH scale
Other indicators
Litmus and other simple indicators just show if a substance is an acid or
an alkali. Universal indicator shows how acidic or alkaline a substance is.
The acidity or alkalinity of a substance is one of its chemical properties.
Universal indicator can change to many different colours. Universal
indicator is made up of a mixture of different indicators.
Type of
substance
Colour of
universal
indicator
strongly acid
red
weakly acid
yellow
neutral
green
weakly alkaline
blue
strongly
alkaline
purple
These strips of paper were soaked in
universal indicator solution and then
dried. The papers were then dipped
into different liquids.
The strength of acids and alkalis is measured on the pH scale.
Universal indicator changes colour and shows the pH of a substance.
The pH of a substance is one of the chemical properties of that substance.
strongly acidic
pH = 1
0
1
weakly acidic
pH = 4
2
3
4
more acidic
neutral
pH = 7
5
6
7
neutral
weakly alkaline
pH = 10
8
9
10
11
strongly alkaline
pH = 13
12
13
14
more alkaline
A colour chart for universal indicator showing the pH scale.
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5 Properties of materials
Questions
6
What does the pH scale measure?
7
What is the pH of a neutral solution?
8
A liquid has a pH of 1. What type of liquid is it?
9
What range of pH do strong alkalis have?
10 What colour does universal indicator turn in a liquid with a pH of 9?
11 Which colours does universal indicator turn in acids?
Think like a scientist
Investigating the pH of different substances
In this task you will test various laboratory chemicals with universal indicator to measure
the pH and what type of chemical it is.
You will need:
universal indicator papers, a range of liquids,
test tubes and a test tube rack, safety glasses
Safety
Read any hazard warning labels and take care not to spill substances on your skin.
Make sure you know what to do if you do spill anything.
1
Put on your safety glasses.
2
Pour a small amount of liquid from a bottle of liquid into a clean test tube.
3
Test with universal indicator.
4
Record the colour of the indicator and the pH.
5
Record the type of each liquid, such as strongly or weakly acidic, neutral, strongly or
weakly alkaline. You could use a table like this one.
Liquid
Colour of universal indicator
lemon juice
salt water
Type of liquid
4
weakly acidic
8
weakly alkaline
green
soap solution
cola drink
pH
yellow
4
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5.6 Indicators and the pH scale
Continued
Self-assessment
How well were you able to decide on the pH? Were the colours easy to match to the
numbers?
What safety considerations did you follow?
Activity 5.6.1
Make your own pH chart
Make your own colour chart to show the colours to which universal indicator changes in
liquids of different pH.
You can do this by arranging different coloured pieces of paper in the correct order,
starting with the colour that universal indicator turns in a liquid of pH 1. You could also
use plain paper and paint or colour it yourself. You could do it on a computer and print
it off in colour.
Try to make it interesting. You can cut out different coloured shapes, such as T-shirts on
a washing line or racing cars on a track. You can do this on a large sheet of paper so that
it can be displayed in your classroom.
On each item, write the pH that the colour represents and state if that pH means strong
acid, weak acid, neutral, weak alkali or strong alkali.
Try to add the names and/or pictures of substances next to various pH values.
Summary checklist
I can identify acids and alkalis by use of indicators.
I can make an indicator.
I can use the pH scale.
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5 Properties of materials
Project: Different steel for different jobs
All over the world people use iron to make many things, such as car bodies and bridges,
and to form the structures of buildings. They don’t use pure iron because it is not strong
enough. Instead, they use an alloy of iron, called steel.
Mixing other substances with iron – such as carbon, chromium and nickel – makes steel.
The amount of carbon used, and the amounts and types of other metals used, make
different types of steel. Some different types of steel are mild steel, medium steel, high
carbon steel and stainless steel.
Find information about the different types of steel.
These questions give you a starting point.
1
What substances and how much are added to iron to form the different types of steel?
2
What are the properties of these different types of steel?
3
What are these different types of steel are used for? You should try to link this with
their properties.
4
Where are these different types of steel made?
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5.6 Indicators and the pH scale
Continued
5
Where do the iron, carbon and other metals needed to make them come from?
Do they have to be extracted or treated in some way before they can be used?
6
What does this mean in terms of the cost of manufacture?
7
Where does the steel get used?
8
What does this mean in terms of transport costs?
9
Can you find out about any other specialist steels?
Present the information to your class.
You could make a poster, a slide presentation, a television interview with a
presenter and an ‘expert’, a newspaper article or you could use any other way
to present your information.
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5 Properties of materials
Check your Progress
5.1 Copy the paragraph and choose words from the list to complete it. Each word may
be used once, more than once or not at all.
5.2 a
b
5.3 a
b
brittle
conduct
cut
ductile
electricity
malleable
metal
ring
Metals are shiny when freshly
or polished. They are strong
and if you tap them they
like a bell. Metals
heat energy and
. Metals are
, which means
they can be beaten into shape. They are
, which means they
can be drawn out into wires.
[6]
Why aren’t ‘silver’ coins made of pure silver?
[2]
Explain, using particle theory, why alloys are harder than the metals they
are made from.
[4]
Which property of metals is most useful when:
i
copper is used for electrical wiring
[1]
ii
gold is used for jewellery
[1]
iii
iron is used to build bridges
[1]
iv
stainless steel is used for cooking pans?
[1]
State three differences between metals and non-metals.
5.4 Marcus has dropped a glass bottle of copper sulfate crystals on the floor and
it has broken into small pieces. He has swept the broken glass and crystals into
a container. Explain how he can separate the mixture of glass and copper
sulfate crystals. Remember to include a list of equipment he needs and
to explain how he will stay safe. You could draw diagrams to help explain.
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[3]
[6]
5 Properties of materials
5.5 Litmus is a dye made from a living organism. It is red in acid. It is blue in alkali.
It is purple in a neutral solution.
a
What is the correct scientific term for a substance that changes colour in
this way?
[1]
b
What colour is litmus in a liquid of pH4?
[1]
c
What colour is litmus in water?
[1]
5.6 This truck is loading acid at a factory.
a
The driver has placed an orange warning notice nearby.
[1]
Explain why this is important.
b
Suggest what could be done if there is an accident and some acid is spilt
on the ground. Explain your answer.
[2]
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5 Properties of materials
5.7 The table gives information about the melting points and boiling points of
some metals and non-metals.
Substance
Melting point in °C
Boiling point in °C
gold
1064
2850
lead
328
1750
copper
1082
2580
helium
−270
−269
oxygen
−219
−183
mercury
−39
357
aluminium
660
2400
nickel
1455
2150
sulfur
119
445
sodium
98
900
a
[2]
Copy and complete these tally charts.
Melting point in °C
Tally
Boiling point in °C
up to 0
up to 0
0 to 499
0 to 999
500 to 999
1000 to 1999
1000 to 1499
2000 to 2999
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Tally
5 Properties of materials
b
[6]
Plot the tallied figures on two separate frequency diagrams.
Use the grid below to help you plan your frequency diagrams.
4
3
Number of metals
and non-metals
SEE QUERY LOG
To help with BOTH diagrams, it
would be more useful here to have
'Temperature in oC' with no numbers
along the axis.
Consider using squared paper rather
than graph paper for bar charts.
Tech-Set: no comment within
the query log. Please advise
2
1
0
up to 0
0–499
500–999
Melting point in °C
1000–1499
Use the tables and your diagrams to help answer the following questions.
c
Which metals and/or non-metals are gases at room temperature of 25 °C?
[1]
d
Which metals and/or non-metals are liquid at room temperature of 25 °C?
[1]
e
Which metals and/or non-metals are solid at room temperature of 25 °C?
[2]
f
Which metal and/or non-metal has the smallest difference between its
melting point and its boiling point?
[1]
Which metal or non- metal has the largest difference between its melting
point and its boiling point?
[1]
g
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6 Earth physics
6
Earth physics
6.1 Sound waves
In this topic you will:
•
learn how sound comes from vibrations
•
discover how particles vibrate in a sound wave
•
find out why sound does not travel in a vacuum.
Getting started
Key words
Work in groups to discuss the answers to these questions.
backwards and
forwards
loudness
medium
particles
pitch
sound wave
speed of sound
1
Give two examples of things that make very loud sounds.
2
Give two examples of things that make very quiet sounds.
3
Give two examples of high-pitched sounds.
4
Give two examples of low-pitched sounds.
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6.1 Sound waves
Where does sound
come from?
Things that vibrate make sounds. To vibrate
means to move backwards and forwards
very quickly.
The men in the picture are hitting drums to
make them vibrate. When the drums vibrate,
the drums make a sound.
If you hit a drum with more force, it vibrates
more. This makes a louder sound.
If you touch the front of your neck while you
are speaking, you can feel a vibration. The
vibration comes from your vocal cords, which
make the sound when you speak.
Hitting a drum causes the drum to vibrate, which makes
the sound.
Loudspeakers produce sounds from television,
radio and music players. If you put small objects
into the paper cone of a loudspeaker, the objects
will bounce around. This shows that the paper
cone in the loudspeaker is vibrating.
Not all sounds are the same.
Sounds can vary in both loudness and pitch.
Thunder makes a sound with a low pitch.
A baby crying makes a sound with a high pitch.
Questions
1
A guitar is a musical instrument
with strings.
Which one of these is needed to make
a sound from the guitar?
Small plastic balls show the vibration of the cone in a
loudspeaker.
Write the letter.
A The guitar is made from wood.
B
The guitar strings vibrate.
C There is air inside the guitar.
D There are metal parts on the guitar.
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6 Earth physics
2
Zara is playing the guitar by plucking a string.
Which statement describes a way that Zara can make the sound louder?
Write the letter.
A Pluck the string with more force.
B
Pluck the string with less force.
C Make the string tighter.
D Make the string looser.
3
Some flying insects make a buzzing sound.
Describe what causes this sound.
Sound waves
Sound travels from a vibrating object to our ears.
This is called a sound wave.
What is a sound wave?
When an object vibrates, it moves backwards and forwards.
Every time the object vibrates forward, the air in front of
the object gets pushed forward.
The particles in the air are
made to vibrate backwards
and forwards in time with
the vibrating object.
vibrating cone
direction of sound wave
When the particles in front
of the object vibrate, those
particles make other particles
in front of them vibrate. This
makes a sound wave.
The speed of sound waves
in air is about 343 metres
per second.
The picture shows how
a vibrating cone in a
loudspeaker makes a
sound wave.
vibration of air particles
in sound wave
A sound wave travels to your ear by the vibration of air particles.
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6.1 Sound waves
The vibrations of the air particles in very loud
sounds can cause damage to the ears.
Vibrations from very quiet sounds can be too small
for the ears to detect.
Sound at a certain pitch can cause damaging
vibrations, even when the sound is not
very loud.
You saw in Topic 3.5 that sound is a way of
transferring energy. Sound waves transfer sound
energy.
The vibration of particles in the air is transferred to
other objects. When the vibration is transferred, the
other objects will start to vibrate.
The glass in the bottom right picture has broken
because of the vibrations of a high-pitch sound.
This boy has thrown some feathers in the air. When they hit the floor
there will be a sound but the vibrations will be too small for his ears
to detect.
These people are wearing ear protection while
working near an aeroplane.
Vibrations from sound can break objects.
Questions
4
Copy the sentence and use the correct word from the list to complete it.
current wind wave stream
Sound travels through air as a sound………………… .
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6 Earth physics
5
Sofia is watching television.
The sound from the television is travelling across
the room, as shown in the diagram.
direction of sound
Which of these arrows shows how the particles in
air vibrate?
Write the letter.
direction of sound
A
6
B
C
D
Thunder can make objects inside a room vibrate.
Explain what causes the objects to vibrate.
7
A fly is walking up a glass window. The fly’s feet make vibrations.
Explain why people cannot hear the sound of the fly walking.
Sound waves on the move
Sound waves travel by making particles vibrate.
Sound will travel though anything that has
particles: gas, liquid or solid.
You can demonstrate this by tapping on a table.
Ask another person to listen to the sound. Then ask
them to put their ear on the table and listen again.
The first part of this demonstration shows that
sound travels through air, which is a gas.
The second part shows that sound travels though
the table, which is a solid.
Sound also travels through liquids.
Animals such as whales and dolphins
communicate with sounds.
Sound vibrations travel easily through solids.
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6.1 Sound waves
Sound waves move the same way in gases, liquids
and solids. The sound wave makes the particles
vibrate backwards and forwards.
The substance that the sound wave moves
through is called the medium. Therefore,
solids, liquids and gases can all be a medium
for sound.
Vibrations in a vacuum
To hear a sound, there must be:
•
a vibration to make the sound
•
a medium containing particles through which
the sound wave can travel.
You saw in Topic 3.3 that a vacuum is a space
where there are no particles.
These dolphins can use sound to communicate under water.
As there are no particles in a vacuum,
there is nothing to vibrate to make a sound wave.
Therefore, sound will not travel in a vacuum.
Space is a vacuum. If sound waves could travel through space, we
would be able to hear the Sun!
Scientists think that the Sun
would make a high-pitched
humming sound, with louder,
low-pitched sounds from time
to time.
bell jar
You can demonstrate that
sound does not travel in a
vacuum. If you put an electric
bell in a glass jar, you can
see it vibrate as it makes
the sound.
If the air is pumped out of
the jar to make a vacuum, you
can see the bell vibrating but
you cannot hear the sound
of the bell.
electric bell
vacuum
to vacuum pump
Sound waves cannot travel in a vacuum as there are no particles to vibrate.
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Questions
8 Which of these can sound travel through?
Tech-Set: in unit 5 page 178.
DYoung commented the following "
left align numbering".
Should this not be a global?
Select all the correct answers. Write the letters.
A solid
B
liquid
C gas
D vacuum
9 The Moon has no atmosphere. People who went to the Moon wore
suits that contained air.
The people who went to the Moon worked close together.
They did work such as hammering and digging.
Explain why the people doing this work could not hear it happening.
10 Science fiction films are made in studios on Earth.
These films often show explosions in space.
There is usually a loud bang when the explosion happens.
Explain whether you would really hear an explosion in space.
Activity
Modelling sound waves
Work in groups or as a whole class.
You will need:
•
a slinky spring for each group (slinky springs made from metal work better than
plastic ones)
•
chalk or small pieces of paper
1
Stretch the spring across a smooth, flat surface such as a long bench or the floor.
2
Use chalk or small pieces of paper to mark positions on the spring. These represent
particles.
3
One person holds one end of the spring and keeps it still.
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6.1 Sound waves
Continued
4
Another person holds the opposite end and moves the end of the spring backwards
and forwards, as shown in the diagram. This will make a wave in the spring.
direction of hand movement
Movement of a slinky spring to show movement in a
sound wave. The black arrows show possible positions of
the chalk marks on the spring.
Questions
In your groups, discuss the answers to these questions.
1
In which direction does the wave in the spring move?
2
Does the whole spring move in that direction?
3
In which direction do the marks that represent particles move?
4
What did the person holding the fixed end of the spring feel from the spring?
•
Did you see the representation of movement of particles in the wave?
•
Did this help you understand how particles in air move in a sound wave?
Think like a scientist
Sound and vibration
You are going to investigate whether sound requires vibrations to travel.
Work in groups of three.
You will need:
2 disposable cups, a sharp object to make a small hole in the bottom of each cup,
a string long enough to go across the classroom, scissors to cut the string
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6 Earth physics
Continued
Safety
Take care when using the sharp object to make a hole in the cups.
1
Pass the string through the holes in the cups so that the open ends of the cups
face away from each other. Make the string as long as possible.
2
Secure the string inside each cup by tying a knot.
3
Set up the equipment as shown in the diagram. This is sometimes called a
string telephone.
4
Pull the string tight between the cups.
5
The person speaking puts the cup over their mouth.
6
The person listening puts the cup over their ear.
7
Speak as quietly as possible, so that the person hears the sound of your voice through
the string.
8
Let the string go slack. Say the same thing, with the same loudness, when the string is slack.
9
Pull the string tight again. The third member of the group should grip the string in
their hand. Do this around the middle of the string and then in different places.
10 Say the same thing, with the same loudness, when the string is being gripped.
Questions
1
State what the sound wave passes through to travel between the cups.
2
Describe the difference in what you heard when the string was tight and when the
string was slack.
3
Describe what happened when the string was gripped in the middle.
4
State whether the position that the string was gripped made any difference to the
sound that you heard.
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6.1 Sound waves
Continued
5
Explain what you can conclude from these observations.
6
It is very difficult to speak with the same loudness each time. Suggest an improvement
for this so that the investigation is a fair test.
Peer-assessment
Swap your answers with a partner.
•
Do your partner’s answers agree with your observations in the investigation?
•
Do you agree with your partner’s conclusion?
•
Do you agree with your partner’s suggestion for making this a fair test?
Summary checklist
I can understand that vibration makes sound.
I can understand that sound travels as a wave.
I can recall how the particles move in a sound wave.
I can recall that sound can travel in solids, liquids and gases.
I can understand why sound does not travel in a vacuum.
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6 Earth physics
6.2 Reflections of sound
In this topic you will:
•
learn that sound waves can be reflected
•
discover what can happen when sound is reflected.
Getting started
Key words
Work in groups.
echo
effect on the
sound
property
reflected
unwanted
Discuss how you would describe the movement of particles in a
sound wave.
For a challenge, try to do this without a diagram and without
moving your hands.
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6.2 Reflections of sound
Reflections
One property of all waves is that they can be reflected
from surfaces. Therefore, sound waves can be reflected.
Reflection is like bouncing a ball off a wall. When a
wave is reflected, the wave behaves like the ball. The
only difference is that a wave is not affected by gravity.
A sound wave travelling towards a wall will hit the
wall and come back.
Sound waves reflect best from large, smooth, flat
surfaces. Surfaces such as glass, tiles, flat metal and
smooth concrete give good reflections of sound.
If you stand between two flat walls you can hear the
reflection from sound. You can do this in an empty
room.
When you clap your hands, you hear a strange effect
on the sound. An effect on a sound means the sound
is changed.
The sound of the clap seems to last longer than
usual, then fade away.
Clapping your hands makes a sound wave. The sound
wave will travel away from your hands in all directions.
When the sound wave hits a wall, it is reflected back.
The reflection of a sound wave is called an echo.
Stand between two flat walls and clap your hands once.
What do you hear?
Reflection of a sound wave is like bouncing a ball –
the wave comes back off the wall.
This room would give good reflections of sound.
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6 Earth physics
sound waves from bat
Useful echoes
reflected sound waves
Echoes can be useful.
Bats use echoes to find insects for food. The bat
makes a sound. The sound wave reflects off the
insect – there is an echo. The bat can work out
where the insect is from the time taken for the
echo to reach the bat, and the direction the echo
comes from.
Boats can use echoes to find the depth of water
under the boat.
A sound is sent from the bottom of the boat. The
sound travels through the water and reflects off the
solid ground. The echo comes back to the boat. The
time taken for the echo to come back can be used to
work out the depth.
The sound wave from the bat (thin lines) echoes off
the insect (wider lines).
Notice that the distance travelled by the sound is
double the distance from the object making the
sound to the reflecting surface. The sound has to travel
from the object to the reflecting surface and back
again. You can see this in the picture of the bat and
insect, and in the picture of the boat.
Echoes can also be used to make images from inside
the body. Sounds sent into the mother’s body echo
back out of her body. This method is used to make
the image of the unborn baby.
Key
sound waves
w
from shi
ship
reflected
sound waves
This image of an unborn baby was made by using echoes.
This boat is using an echo to check the depth of the water.
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6.2 Reflections of sound
Unwanted echoes
Sometimes echoes are unwanted. For example, when recording music,
echoes change the sound. A musical note that is played once will repeat
with an echo. This effect will spoil the recording.
A room with large flat walls would give many echoes.
The picture on the left shows how the walls of a room are changed to
stop echoes. This room can now be used to record music without the
effect of echoes.
In a theatre, the audience needs to hear the voices of people on the stage.
If there were echoes in a theatre, the voices would not be clear. Theatres
are designed to stop echoes. Theatres usually have no large flat surfaces
that could cause echoes.
The shapes on the walls of this room are made to
stop echoes.
The design of this theatre will stop echoes.
Questions
1
Which statement describes what happens to a sound to make
an echo?
Write the letter.
A The pitch of the sound increases.
B
The pitch of the sound decreases.
C The sound gets reflected.
D The sound gets louder.
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6 Earth physics
2
Which one of these will give the best echo in a room?
All of the materials have the same area.
Write the letter.
A soft curtains
B
glass window
C thick carpet
D wool blanket
3
Arun goes to the same music concert in two different theatres, A and B.
The theatres are shown in the pictures.
A
B
Arun says the music sounded better in theatre B.
Use information in the pictures to explain why the music sounded
better in theatre B.
4
Zara has an empty room where she can practise playing her drums.
Which one of these materials could she put on the walls to stop
echoes when she plays?
Write the letter.
A flat wood sheets
B
shiny metal sheets
C soft thick curtains
D large flat mirrors
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Tech-Set: Please advise as there has been no
instances of "Extension question" being used in any
of the previous books.
6.2 Reflections of sound
Extension question. You can calculate the
distance that a sound wave has travelled using
a formula in this question.
5
You do not need to learn this until you study
Cambridge Lower Secondary Science Stage 8.
A fishing boat uses an echo to find the
distance from the boat to some fish.
reflected
sound waves
sound waves
from ship
A sound is sent from the ship to the fish.
The sound reflects back to the ship.
The speed of sound in water is 1500 metres
per second.
The time taken for the sound to go from the ship and back to the
ship is 0.2 seconds.
Use this equation to calculate the distance from the boat to the fish:
distance = speed × time
Remember that the distance travelled by the sound wave in 0.2
seconds is from the ship to the fish and back again.
Activity
Modelling echo location
Some animals, such as bats and dolphins, use echo location to find food. In this activity,
you will use light and a mirror to model echo location.
You will need:
a small plane mirror that can be propped up vertically, a flashlight or ray box,
a piece of card or wood that will cover the mirror when placed horizontally,
four items to support the piece of card over the mirror
You need to work in pairs, as learner A and learner B. Then swap roles.
Learner A
1
Place the mirror vertically on a desk without letting your partner see.
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6 Earth physics
Continued
2
Place the card over the mirror. Support it so that the mirror cannot be seen,
as shown in the diagram.
light from flashlight or ray box
sheet of card
light source
moved to
locate mirror
position of mirror
under card
Learner B
1
Look at the apparatus from above, so that you cannot see where the mirror is.
2
Use the flashlight or ray box to locate the mirror.
3
Attempt to find:
•
where the mirror is, as accurately as possible
•
what direction the mirror is facing.
Questions
1
In this model, the light represents the sound made by the dolphin or bat.
State what the mirror represents.
2
Make a list of:
a
strengths of this model in representing echo location
b
limitations of this model in representing echo location.
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6.2 Reflections of sound
Think like a scientist
How is sound reflected?
You are going to investigate how sound is reflected.
Work in groups of two or three.
You will need:
2 plastic or cardboard tubes and a mobile phone, a large sheet of paper, or 2 A4
sheets taped together, a block or piece of hard plastic, metal or a tile for a reflecting
surface, piece of wood for a barrier, a piece of soft material, such as foam or
polystyrene as another reflecting surface
1
Set up the apparatus as shown in the diagram.
reflecting surface
barrier
paper
mobile phone
cardboard tubes
2
Set the mobile phone to make a quiet sound that you can hear. Place the mobile
phone as close as possible to, or inside, one of the tubes. Put the other end of this
tube close to the reflecting surface.
3
Mark the position of this tube on the paper.
4
Set the other tube so one open end is close to the reflecting surface and also close to
the other tube.
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6 Earth physics
Continued
5
Put your ear to the end of this tube. Turn this tube until the sound from the mobile
phone sounds loudest.
6
Mark the position of this tube on the paper.
7
Repeat the investigation with the first tube (containing the mobile phone) in a
different position.
8
If you have time, change the reflecting surface.
Questions
1
Describe any trend or pattern you noticed in the positions of the tubes.
2
Describe the observations you made if you changed the reflecting surface.
3
If you did not have time to change the reflecting surface, suggest:
•
one surface that would be good for reflecting sound
•
one surface that would be bad for reflecting sound.
This investigation can be difficult to do.
Make a list of things you found difficult in this investigation.
Try to suggest improvements that could:
•
make the investigation easier
•
give better results.
Summary checklist
I can understand that sound can be reflected.
I can recall what happens when sound is reflected.
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6.3 Structure of the Earth
6.3 Structure of the Earth
In this topic you will:
•
describe a model of the structure of the Earth
•
understand how the continents on Earth have changed.
Getting started
Key words
Draw and label a diagram to show what the Earth would look like
if it were cut through.
continental
core
crust
drift
magma
mantle
molten
tectonic plates
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6 Earth physics
What do we know about the Earth?
Scientists have worked out that the Earth is about 4500 million years
old. They have also worked out what is inside the Earth.
The Earth has a crust of solid rock.
Under the crust is the mantle, which is molten (hot liquid) rock that
can flow.
In the centre of the Earth is the core. It is made of the metals nickel
and iron. The outer part of the core is molten. The inner part of the
core is solid.
The rocks found in the crust contain metals and non-metals. The pie
chart below on the right shows the approximate proportions of the
most common elements in the Earth’s crust.
aluminium, Al
crust (solid rock)
mantle (molten rock)
iron, Fe
silicon, Si
calcium, Ca
outer core (molten metals,
mostly iron and nickel)
others
inner core (solid metals,
mostly iron and nickel)
oxygen, O
Questions
1
State the name of the part of the Earth that forms the centre.
2
Name the metals found in this part.
3
Name the most common non-metal in the Earth’s crust.
4
Name the most common metal in the Earth’s crust.
People used to think that the Earth was only a few thousand years old.
They thought the Earth had never changed.
In 1912, a German scientist called Alfred Wegener suggested that,
millions of years ago, all the land was one large continent. Over
millions of years the land broke up and drifted apart. This idea is called
continental drift.
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6.3 Structure of the Earth
His evidence for this idea was that:
•
the shapes of the continents fit together
•
the types of rock on the different continents match up where
they fit together
•
the fossils on the different continents match up where they
fit together.
Wegener could not explain how continental drift happened,
so not everyone believed his ideas.
Laurasia
Pangea
Gondwana
150 million years ago
225 million years ago
North
America
South
America
Europe
Asia
North
America
Africa
Europe
Asia
Africa
India
South
America
India
Australia
Antarctica
Australia
Antarctica
100 million years ago
Earth today
These drawings show how the continents have drifted apart over a very long time.
We now know that the Earth’s crust is made up of large tectonic plates.
Some of the plates are under the oceans: they are called oceanic plates.
Some of the plates form the continents: they are called continental plates.
These tectonic plates move slowly on the liquid rock called magma
beneath them. This is how continental drift occurs.
The plates only move about 4 cm each year, which is about same speed
as your fingernails grow.
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6 Earth physics
Key
plate boundary
Juan de
Fuca plate
Eurasian plate
North American
plate
Arabian
plate
Caribbean
plate
Cocos plate
Pacific
plate
Pacific
plate
Philippine
Sea plate
Indian
plate
African plate
Nazca
plate
South
American
plate
Indo-Australian plate
Antarctic plate
Scotia plate
The red lines show the edges of the tectonic plates.
Questions
5
What evidence did Wegener have for his idea of continental drift?
6
Why did some people reject his idea?
7
Which tectonic plate do you live on?
8
What causes the tectonic plates to move?
Activity 6.3.1
Drifting plates
You are going to model continental drift.
You will need:
some pieces of polystyrene, water, a large heat-proof dish,
something to heat the water, such as a Bunsen burner
Safety
Take care when heating the water, as the dish may get very hot.
1
Pour some water into the heat-proof dish.
2
Place the pieces of polystyrene on the water. Wait for them to stop moving.
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6.3 Structure of the Earth
Continued
3
Heat the water gently.
4
Observe what happens.
polystyrene pieces
heat-proof dish
water
electric hot plate
Questions
1
2
In your model for continental drift, state what is represented by:
a
the polystyrene
b
the heat source
c
the water.
Explain the strengths and weaknesses of this model of continental drift.
Summary checklist
I can describe the structure of the Earth.
I can state the evidence for continental drift.
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6 Earth physics
6.4 Changes in the Earth
In this topic you will:
•
explain how fold mountains and volcanoes are formed
•
explain how earthquakes happen.
Getting started
Key words
Work with a partner.
active
dormant
earthquake
extinct
fold mountains
geological
change
inactive
lava
magnitude
plat boundary
subduction
volcano
Make a list of ways that mountains and volcanoes are:
1
the same
2
different.
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6.4 Changes in the Earth
Geological change
The places where tectonic plates meet are called plate boundaries.
Geological change happens at plate boundaries. This is because the
tectonic plates are always moving. Some of the geological change is very
slow – it happens over millions of years. But some of the geological
change is very sudden and violent.
This illustration shows the plate boundaries around the edge of the
Pacific Ocean. There are many geological changes and events, such as
volcanic eruptions and earthquakes, here. This area is often called the
Pacific Ring of Fire.
Key
plate boundary
ring of fire
Eurasian plate
North American plate
volcano
Caribbean
plate
Philippine
Sea plate
Cocos
plate
Pacific plate
Nazca
plate
Indo-Australian plate
South
American
plate
Pacific Ring of Fire
Movement of plates
The movement of tectonic plates creates three types of plate boundaries.
Plates moving together
One plate may slide underneath
the other one. This is called
subduction. The rocks in the
Earth’s crust melt as they move
into the mantle. They become
part of the mantle.
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6 Earth physics
Plates moving apart
As tectonic plates drift away
from each other, they break and
crack when they become too
thin. Lava (liquid rock) erupts
from the mantle and hardens to
form new crust with new rocks.
This causes a volcano.
Plates sliding past
Because the plates are
very large and heavy, there
is a lot of friction between
the plates. Over the years,
this makes the plates stick
together. There is always
force on the tectonic plates,
so the pressure builds up and
eventually the pressure causes
violent movement. This is an
earthquake.
Fold mountains
Sometimes, when tectonic plates move
together, the rocks crumple and fold
upwards. The mountains that this produces
are called fold mountains.
rock layers pushed
into folds
This can happen under the ocean or
on land.
The newest fold mountains are between
10 and 25 million years old. These include
the Himalayas in Asia and the Rocky
Mountains in North America. The
oldest fold mountains are more than 200
million years old. These include the Ural
Mountains in Russia.
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compression from
tectonic plate movement
6.4 Changes in the Earth
The Himalayas, Rocky Mountains and Ural Mountains were all formed when tectonic plates pushed against each other.
Volcanoes
ash cloud
Volcanoes are usually formed at the plate
boundaries when magma from the mantle
rises up through cracks in the Earth’s crust.
At the Earth’s surface, magma erupts to
form lava flows and ash deposits. Magma
is the name for liquid rock when it is
underground. Lava is the name for liquid
rock when it is on the surface. The lava
and ash harden as they cool to form new
rocks. So each time the volcano erupts, it
gets bigger.
Sometimes, if the magma is really thick,
and contains dissolved gas, pressure builds
up and the eruption is violent. Gases and
rock shoot up through the opening. Violent
eruptions can even cause avalanches and
earthquakes – and tsunamis if the volcano
is close to the sea.
crater
secondary vent
lava flow
layers of ash and lava
main vent
magma
The parts of a volcano.
Some volcanoes are active and may erupt
at any time. Some volcanoes are inactive or
dormant, which means they have not erupted
for a very long time. Other volcanoes are
extinct, which means they will not
erupt again.
A powerful eruption at Anak Krakatau volcano, Indonesia. Part of
the volcano was blown off into the sea, causing a tsunami.
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6 Earth physics
Earthquakes
Some earthquakes are extremely violent and
cause a lot of damage. Some are so slight that
they only register on scientific instruments.
The size or magnitude of the earthquake
depends on the size of the faults at the plate
boundaries, and how far the rocks move
when the earthquake happens. In the largest
earthquakes, the rocks can move tens of
metres in seconds.
Questions
1
Earthquakes can cause damage to roads and buildings.
Which statement is true about tectonic plates?
Write the letter.
A They never move.
B
They move in different ways.
C They always move towards each other.
D They always move away from each other.
2
Explain how tectonic plates can cause fold mountains to form.
3
Which word is used to describe the strength of an earthquake?
Write the letter.
A force
B
energy
C magnitude
D destruction
4
Explain what causes an earthquake.
Activity
Model for moving tectonic plates
Try out these models to show what happens where tectonic plates meet.
You will need:
a large piece of cloth, 2 pieces of paper, modelling clay ,2 chocolate bars with
soft centres (not solid chocolate)
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6.4 Changes in the Earth
Continued
Model A
Place a large piece of cloth on the table.
Place your hands flat on the cloth, about 30 cm apart. Push your hands together.
Model B
Place two pieces of paper flat on the table so that they are touching. Push them together.
Can you make them slide so that one piece goes over the other one? This is similar to
what happens when one tectonic plate slides over another. Can you make the pieces of
paper form mountains?
Model C
Use modelling clay and make two flat pieces. Place them on the table and then push
them together. What happens?
Model D
Push the two chocolate-covered bars together. What happens?
Questions
For each of the models you used:
1
Describe what happened.
2
Explain what it was modelling.
3
Discuss the strengths and limitations of the model.
4
Could you improve that particular model in any way?
5
Which do you think was the best model? Why?
Summary checklist
I can describe how fold mountains are formed.
I can explain how earthquakes occur.
I can describe how volcanoes are formed.
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6 Earth physics
6.5 Solar and lunar eclipses
In this topic you will:
•
find out how solar eclipses happen
•
find out how lunar eclipses happen.
Getting started
Key words
Discuss the answers to these questions. Work in groups of three
or four.
lunar eclipse
opaque
partial
ray
shadow
solar eclipse
total
1
Which of these describes how light travels?
in curved paths in straight lines in circles randomly in straight and curved paths
2
Explain how a shadow is formed.
3
Decide whether each of these statements is true or false.
The Moon gives out its own light.
The Sun gives out its own light.
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6.5 Solar and lunar eclipses
Shadows
An opaque object is an object that
will not allow light to pass through.
When an opaque object passes in
front of a source of light, a shadow
will form.
Look at the shadow of the aeroplane
in the picture. The shadow looks
dark because the light from the Sun
has been blocked from reaching the
ground. The aeroplane is made from
metal which is opaque.
The grass around the shadow looks
brighter because light from the Sun is
reaching those areas.
The aeroplane is opaque so it makes a shadow on the ground.
The next picture shows how the shadow is formed.
aeroplane in the air
rays of light from the Sun
shadow on the ground
Light travels in straight lines called rays. Light rays from the Sun cannot
pass through the aeroplane, so light rays that reach the aeroplane cannot
reach the ground.
Imagine you were standing on the grass. When the shadow of the
aeroplane passes you, it will seem to go dark. When the shadow has
gone, it will get brighter again.
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6 Earth physics
Solar eclipse
A solar eclipse happens when the Moon
comes between the Sun and the Earth.
The Moon is made from rock, so is an
opaque object. The Moon blocks the
rays of light coming from the Sun.
total solar eclipse
is seen here
Sun
rays of light
from the Sun
partial solar eclipse
is seen here
Moon
Earth
The shadow of the Moon forms on the
Earth.
The diagram shows how the shadow of
the Moon is formed on the Earth. In the
middle of the shadow, all the light rays
from the Sun are blocked. People in the
middle of the shadow observe a total
solar eclipse.
A solar eclipse happens when the Moon comes between the Sun and
the Earth.
The left picture shows what a total solar
eclipse looks like.
Away from the middle of the shadow of
the Moon, some of the light rays from
the Sun can reach the Earth. Away from
the middle of the shadow there is a
partial solar eclipse.
A total solar eclipse is seen from
the middle of the
Moon’s shadow.
The right picture shows what a partial
solar eclipse looks like.
The picture below shows a series of photographs taken as the Moon
passes between the Earth and the Sun.
The picture on the next page shows what a solar eclipse looks like from
space. The dark part of the Earth is in the shadow of the Moon. At the
centre of the shadow, there is a total solar eclipse. Away from the centre,
there is a partial solar eclipse.
The Moon is passing between the Sun and the Earth in these photographs.
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A partial solar eclipse is seen
away from the middle of the
shadow of the Moon.
6.5 Solar and lunar eclipses
You must never look directly at the Sun, even when there is an
eclipse. The light from the Sun is very bright and can cause
permanent damage to your eyes.
Lunar eclipse
A lunar eclipse happens when the Earth comes between the
Sun and the Moon.
The Earth is also an opaque object, so the Earth blocks the
light from the Sun. The shadow of the Earth is formed on
the Moon.
The diagram shows how the shadow of the Earth forms on
the Moon.
The dark part of the Earth is in the shadow of
the Moon. People here see a solar eclipse.
The picture shows a series of three photographs of the
shadow of the Earth passing across the Moon.
You might think that solar and lunar eclipses should happen every
month. The Moon takes 28 days to orbit the Earth, but the orbit of the
Moon is tilted slightly. The orbit of the Moon is not exactly in the same
plane as the orbit of the Earth around the Sun.
It is only when the Sun, Earth and Moon are in the same straight line
that eclipses can happen.
partial lunar
eclipse when
Moon is here
Sun
rays of light from the Sun
Moon
Earth
orbit of Moon
total lunar
eclipse when
Moon is here
partial lunar
eclipse when
Moon is here
A lunar eclipse happens when the Earth comes between the Sun and the Moon.
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6 Earth physics
The Earth is passing between the Sun and the Moon in these photographs.
Questions
1
Which of these describes how a solar eclipse happens?
Write the letter.
A The Sun comes between the Moon and the Earth.
B
The Earth comes between the Moon and the Sun.
C The Moon comes between the Earth and the Sun.
2
Which of these describes how a lunar eclipse happens?
Write the letter.
A The Sun comes between the Moon and the Earth.
B
The Earth comes between the Moon and the Sun.
C The Moon comes between the Earth and the Sun.
3
Explain why a solar eclipse can only ever be seen in the daytime.
4
Write true or false for this statement.
A total lunar eclipse can only ever be seen in the daytime.
Explain your answer.
Activity 6.5.1
Classroom eclipses
In this activity, you will make models to show how eclipses happen.
Work in groups of four or five.
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6.5 Solar and lunar eclipses
Continued
You will need (per group):
an electric lamp and power supply – 12 V lamps work well, a white soccer ball,
a tennis ball, a paper cup, a light string or thread, adhesive tape
Safety
Take care not to touch the lamp because it will be hot.
You need to work in a shaded position in the room. You should turn the classroom lights
off. If your classroom has blinds or curtains, these should be closed.
In your model:
•
the electric lamp will be the Sun
•
the white soccer ball will be the Earth
•
the tennis ball will be the Moon.
1
Attach the string to the tennis ball with the adhesive tape.
2
Place the soccer ball on the plastic cup. This will lift the ball off the desk and also stop
the ball from rolling.
3
Place the lamp about 50 cm from the soccer ball. Switch on the lamp.
4
One side of the soccer ball should be lit from the lamp. The other side of the soccer
ball should be in the shade.
Questions
1
In your model, which side of the Earth is in the day and which side is in the night?
Hold the string so the tennis ball hangs down.
Move the tennis ball between the lamp and the soccer ball. The shadow of the tennis ball
should be seen on the soccer ball.
2
What type of eclipse is the model showing?
3
Point out where there is a total eclipse and where there is a partial eclipse.
Now move the tennis ball to the other side of the soccer ball. Make sure the tennis
ball is in the shade of the soccer ball.
4
What type of eclipse is the model showing now?
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6 Earth physics
Continued
Self-assessment
Give each of these statements a number from 1 to 5.
1 means ‘strongly disagree’ and 5 means ‘strongly agree’.
•
I understood why a lamp was used to model the Sun.
•
I understood why the model of the Earth was bigger than the model for the Moon.
•
I understood how the model showed a solar eclipse.
•
I understood how the model showed a lunar eclipse.
•
How did you decide which type of eclipse happened in
your model?
•
How well do you think the model showed eclipses?
Think like a scientist
Making predictions about eclipses
In this task, you will think about making observations and using them to make predictions.
Astronomers in the Middle East made the earliest known predictions of when eclipses
would happen. The astronomers were working about 3000 years ago.
1
List the facts that need to be given when making a prediction about an eclipse.
2
These astronomers 3000 years ago knew that the pattern of solar eclipses
repeats after every 223 lunar months.
One lunar month is 29.5 days.
Calculate the number of days in 223 lunar months.
3
Suggest what must happen to the Sun, the Moon and the Earth every
223 lunar months.
4
Explain how a pattern of observations can be used to make future predictions.
5
Scientists working in the present day have predicted eclipses into the future.
Scientists think these predictions are accurate until 17 April 3009.
Describe how the accuracy of an eclipse prediction can be tested.
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6.5 Solar and lunar eclipses
Continued
6
Suggest why the accuracy of
eclipse predictions decreases
as the time into the future of
the prediction increases.
7
Scientists working in the present
day have also calculated when
eclipses happened in the past.
There was a battle in Greece in
the year 585 BCE. People at that
time recorded that there was an
eclipse during the battle.
Scientists in modern times have
worked out that the battle
happened on 28 May 585 BCE.
Explain how scientists can use
information about the eclipse
to work out the exact date of
the battle.
8
A solar eclipse occurred during a battle in Greece in 585 BCE.
What type of eclipse is shown in
the photograph?
Explain your answer.
Summary checklist
I can understand how a solar eclipse happens.
I can understand how a lunar eclipse happens.
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6 Earth physics
Project
Volcanoes and earthquakes
The actions of volcanoes and earthquakes change the rocks and the shape of the
land on Earth.
You have four tasks to complete in your group.
1
Make a model to show how a volcano erupts or an earthquake takes place.
You may use any materials you choose but you need to label the parts.
2
Explain how the volcano erupts or an earthquake takes place. You can do this by
making a poster or writing a statement as if you are an expert who needs to explain,
to a journalist, why a recent volcanic eruption or earthquake has happened.
3
Research a recent volcanic eruption or earthquake. Write a report about:
•
the immediate damage it has caused, and how this affects people
•
the long-term effects to the lives of people, plants and wildlife in the area.
You will present your model and explanations to the whole class.
4
Research how scientists detect movements in the Earth’s crust. Include how
this technology:
•
has developed over the last 2000 years
•
can be used to make predictions about earthquakes and volcanic eruptions.
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6 Earth physics
Check your Progress
6.1 Which of these is needed for a sound to be made?
[1]
heat light liquid vibration
6.2 Arun drops his pen on the floor. Sofia hears the pen hit the floor.
Copy the sentences and use words from the list to complete them.
[2]
You can use the words once, more than once or not at all.
the pen sound wave Sofia’s ears air particles
A ………………… travels from ………………… to ………………… .
The ………………… travels through the ………………… .
6.3 Draw an arrow to show the direction of a sound wave. Your arrow can be in any direction.
Now show the direction of movement of the particles in your sound wave.
[3]
6.4 A slinky spring can be used to show how particles move in a sound wave.
Which of these describes this use of a slinky spring?
[1]
modelling predicting concluding observing
6.5 a
Match the parts of the of the Earth’s structure, A–D, with the descriptions, W–Z.
[2]
Parts of the Earth’s structure
A Inner core
B Outer core
C Mantle
D Crust
Descriptions
W molten iron and nickel at the centre
X solid outer layer of the Earth
Y molten rock below the crust
Z solid iron and nickel at the centre of the Earth
b
[2]
What are tectonic plates?
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6 Earth physics
6.6 State what can happen when tectonic plates rub against each other in opposite
directions.
[1]
6.7 Describe how new fold mountains form.
[2]
6.8 Copy the sentence and use words from the list to complete it.
Each word can be used once, more than once or not at all.
[2]
light the Sun the Moon shadow
A solar eclipse happens when the ………………… of ………………… forms on
the Earth.
6.9 Make two copies of this diagram. Your copies do not have to be accurate.
Earth
Sun
a
Add the Moon to your first diagram to show how a lunar eclipse happens.
[1]
b
Add the Moon to your second diagram to show how a solar eclipse happens.
[1]
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7
Microorganisms
in the environment
7.1 Microorganisms
In this topic you will:
•
learn about the different kinds of microorganism
•
grow some microorganisms on agar jelly.
Getting started
Key words
Work individually to answer these questions.
agar jelly
algae
bacteria
colony
fungi
microorganism
mushroom
Petri dish
protozoa
single-celled
sterile
toadstool
yeast
1
Some bacteria can cause diseases in humans.
Can you name two diseases caused by bacteria?
2
What other kinds of organisms can cause disease?
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7 Microorganisms in the environment
What is a microorganism?
A microorganism is a living organism that is so small that you can only
see it clearly by using a microscope.
Like all living organisms, microorganisms are made of cells. Many
microorganisms are made of only one cell: they are single-celled.
There are several different kinds of microorganism. They include
bacteria, microscopic fungi, protozoa and algae. Each of these
microorganisms is described later in this topic.
Bacteria
Bacteria are everywhere. (Bacteria is a plural
word. The singular word, for just one of them,
is bacterium.)
Each bacterium is made of a single cell. Cells
of bacteria are much smaller than animal cells
or plant cells. You could fit 1000 of the bacteria
in the photograph, lined up end to end, between
two of the millimetre marks on your ruler.
Most bacteria are harmless but there are a few
kinds that can make you ill.
These bacteria live in our digestive systems. They are
completely harmless.
Fungi
Fungi (singular: fungus) are not always
microorganisms. Many fungi, including
mushrooms and toadstools, are large and
easy to see.
Mushrooms and toadstools are only part
of the fungus’s body, though, and they only
grow at certain times of year. Most of the
time, the fungus is just a tangle of very thin
threads. The threads often grow under the
ground, or inside a dead log. The threads are
so thin that they are difficult to see without
a microscope.
There are also some kinds of fungi that do not
produce mushrooms or toadstools. They are
made of single cells, not threads, so they are
The white ‘powder’ on these grapes is yeast. The yeast cells
feed on sugar in the grapes.
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7.1 Microorganisms
definitely microorganisms. The powdery substance
that you sometimes see on the surface of grapes
is made up of millions of cells of yeast, which is a
microscopic fungus.
Questions
1
Viruses are even smaller than bacteria.
Suggest why they are not usually said to
be microorganisms.
2
We can see yeast on the surface of
fruit. Why is yeast classed as a microorganism?
Growing microorganisms
A single microorganism is too small to see without
a microscope, but when left to grow, a single cell of
a bacterium or fungus divides repeatedly to make a
collection of many cells. This collection of cells is
called a colony. The colonies are big enough for you
to see without a microscope.
This is a group of yeast cells seen through a
microscope. If you look closely, you can see little buds
growing out of some of the cells. This is how yeast
reproduces. Yeast is a microscopic fungus.
This can be done safely in the laboratory. Scientists let
microorganisms grow in a Petri dish containing a
special kind of jelly, called agar jelly.
The dish and the jelly have to be sterile. This means
that any living organisms on them have been killed.
Petri dish
agar jelly
Think like a scientist
Growing microorganisms from the air
Microorganisms are so small that they can float around in the air. You cannot see them,
but they are there. In this experiment, you will use agar jelly to grow some bacteria and
fungi from the air.
You will need:
a sterile Petri dish containing sterile agar jelly,
some sticky tape, a pen that can write on plastic
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7 Microorganisms in the environment
SEE QUERY LOG
Sorry, but I have no idea what this sentence means. Please rewrite to
make some sense.
Continued
Tech-Set: Please advise as no comments in the query log!
Safety
Do not breathe or talk over the top of the jelly. You do not want to grow bacteria from
your breath.
It is very unlikely that any of the bacteria or fungi that you grow are harmful. But – just in
case – keep the lid on the Petri dish after step 2. That way, you cannot accidentally touch
them or breathe them in.
Read the safety notes before you start.
1
Take the lid off the dish. Leave the dish open for about
5–10 minutes. This allows microorganisms in the air to
get onto the jelly.
2
Put the lid back on the dish. Use sticky tape to fasten the
lid onto the dish.
3
Turn the dish upside down. This is so that any
droplets of water that form inside the dish do not make puddles on the jelly.
The puddles might drown the microorganisms.
4
Label the bottom of the dish with your name and the date.
5
Leave the dish in a safe place for a few days. Do not take the lid off the dish.
6
After a few days, look at the surface of the jelly
in the dish. You will see colonies of bacteria and
fungi growing on the jelly. Each colony began as
a single microorganism.
taping the lid onto the dish
Questions
1
The jelly contains nutrients for the
microorganisms. Can you suggest what the word
‘nutrients’ means? (You will find out more about
nutrients in Topic 7.4.)
2
Suggest why the Petri dish and agar jelly must
be sterile.
3
Make a drawing of the colonies of
microorganisms on the surface of the jelly. You
may have some colonies of bacteria, and some
colonies of fungi. Label them.
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Colonies of bacteria usually have smooth
edges. Colonies of fungi are usually furry, or
have rough edges.
7.1 Microorganisms
Microscopic algae and protozoa
If you look at some pond water through a microscope, you will see many
tiny living organisms in the water. Some of them are tiny plant-like
organisms, called algae. Some of them are animal-like organisms, called
protozoa. (The singular forms of these two words are alga and protozoan.)
These microorganisms are in a drop of pond water.
Questions
3
Some of the microorganisms in the photograph are not single-celled.
How are their cells arranged?
4
Some of these microorganisms have cells like animal cells, and some
have cells like plant cells.
a
Make a simple drawing of one of the microorganisms that has
cells like animal cells.
b
Make another simple drawing of one of the microorganisms
that has cells like plant cells.
c
Label your drawings to explain the differences between them.
Summary checklist
I can explain what a microorganism is.
I can name some different kinds of microorganism.
I can describe how to grow microorganisms on agar jelly.
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7 Microorganisms in the environment
7.2 Food chains and webs
In this topic you will:
•
practise constructing food chains and food webs, using
arrows to indicate energy transfer
•
practise using the correct terms to describe the organisms in
a food chain or food web
•
think about how well food chains and food webs describe
feeding relationships.
Getting started
Key words
Try to answer these questions on your own.
carnivore
consumer
ecology
food chain
food web
herbivore
predator
prey
producer
1
Tigers eat deer. Deer eat grass. Write this as a food chain.
2
Tigers also eat langur monkeys. Deer are also eaten by
leopards. Add those animals to your food chain to make a
food web.
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7.2 Food chains and webs
Microorganisms in the environment
The study of organisms in their environment is called ecology. All the
different organisms that live together affect one another in some way.
For example, one species of animal may eat another animal. A plant
may provide shelter for an animal.
Microorganisms have important roles to play in the environment. In
the rest of this Unit, we will look at how microorganisms affect other
organisms in their environment, including their importance in food
chains and food webs.
In this topic, you will look at how food chains and food webs describe
how energy, in the form of food, is transferred between animals and
plants. In the next topic, you will look at how microorganisms fit into
food chains and food webs.
Food chains
Arun has chicken and rice for lunch. It gives him a lot of energy.
The food you eat gives you energy.
How did the energy get into the food?
The energy in food begins in the Sun. Energy from the Sun reaches the
Earth in sunlight.
Plants use energy from sunlight to make their own food. Some of the
energy from the sunlight goes into the food that the plant stores in its
roots, stems, fruits and leaves.
When an animal – such as Arun – eats part of the plant, it eats the food
the plant made. This is how the animal gets energy. This is called energy
transfer.
You can show how the energy passes from the Sun into the rice, and
then into Arun’s body, by drawing a food chain.
The arrows in the food chain show how energy is passed from the Sun to
the plant, and then is transferred to the rice, and then to Arun.
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7 Microorganisms in the environment
The first organism in a food chain is a producer. Plants use energy from
the Sun to produce food.
All the other organisms in a food chain are consumers. Animals are
always consumers. They have to eat ready-made food to get their energy.
They consume (eat) plants or other animals.
Consumers that consume only plants are herbivores.
Consumers that consume other animals are carnivores.
Animals that catch, kill and eat other animals are predators. The animals
they eat are their prey.
Questions
1
The chicken that Arun ate for lunch ate wheat. Wheat is a plant.
Draw a food chain showing how the energy passed from the Sun to
Arun when he ate the chicken.
2
Draw a food chain showing how energy from the Sun passed into you
when you ate one of the things that you had for breakfast or lunch.
Food webs
Here are two more food chains. These food chains describe part of
the feeding network of plants and animals on the African plains.
acacia tree
grass
springbok
termite
cheetah
aardvark
leopard
The diagram on the next page shows how the organisms in these two
food chains, and some other organisms, are connected by their feeding
habits. This diagram is a food web.
Put your finger on the acacia tree in the food web. Then move it to the
springbok, then to the cheetah. You are tracing the path of the energy as it
transfers along a food chain.
Now do the same for another food chain – the one that begins with grass
and ends with a leopard.
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7.2 Food chains and webs
leopard
cheetah
hyena
aardvark
springbok
zebra
acacia
termite
grass
A food web on the African plains.
Questions
3
Write down two more food chains that you can find in the food
web diagram.
4
Write the names of the two producers in the food web.
5
How many consumers are there in the food web?
6
How many herbivores are there in the food web?
7
Write the names of two carnivores from the food web.
8
Write the names of two predators and their prey, from the food web.
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7 Microorganisms in the environment
Activity
Describing a food web
Work in a group of four or five. Your task is to write a series of descriptions that someone
else can use to build a food web using the cards and arrows.
You will need:
•
a diagram of a food web (each group needs a
different food web to work with)
•
some cards that you can write on
•
some lined paper
•
some arrows cut out of card or paper
1
Write the names of the organisms in the food web on the cards, one name on each
card.
2
Write the descriptions on lined paper. For example, for the African food web, some of
your descriptions could be:
Springbok eat acacia trees.
Termites are eaten by aardvarks.
Cheetahs and leopards eat zebras.
3
When your group has finished writing the descriptions, take your cards and arrows to
another group. Ask this group to use your descriptions to build the food web.
Self-assessment
Could the other group use your descriptions to build the food web?
Did they make the arrows point the correct way?
How do you think you could make your descriptions easier to follow?
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7.2 Food chains and webs
Think like a scientist
Using a food web as a model
A food chain or a food web is a model. It tries to show how plants and animals that live in
the same place depend on each other for food.
In your group of two or three, discuss how well you think the African food web shows what
really happens on the African plains. Here are some ideas you could discuss.
•
How complete do you think the food web is?
•
Is it possible to draw a totally complete food web?
Question
1
When you have finished your discussion, copy and complete these sentences.
I think the food web is a useful model because ……………… .
I think the food web is not a perfect model because ……………… .
Summary checklist
I can use descriptions to construct a food chain or a food web.
I can use arrows to show how energy transfers from one organism
to another.
I can classify the organisms in a food web as producers, consumers,
herbivores, carnivores, predators or prey.
I can describe some strengths and limitations of food chains and
food webs as models.
Tech-Set: Please note that
200134392-001 is the above image
AND it has been used as section
7.2 opener image. Please advise.
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7 Microorganisms in the environment
7.3 Microorganisms and decay
In this topic you will:
•
learn about microorganisms and decay
•
investigate how temperature affects the rate of decay
•
plan an experiment to test an hypothesis about decay.
Getting started
Key words
In a group of three, think of three different ways to complete
this sentence:
decay
decomposer
mould
organic matter
rot
A microorganism is ………………… .
Be ready to share your ideas with the rest of the class.
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7.3 Microorganisms and decay
Decomposers and decay
The food chains and food webs that you looked at in
the previous topic did not include microorganisms. But
microorganisms are everywhere. They live in the air, in the
soil, in water, on our skin and inside our bodies.
The apple in the picture has microorganisms growing on its
surface. Each spot on the apple is made up of millions of cells
of microscopic fungi. This kind of fungus is sometimes called
mould. The apple is mouldy.
The microorganisms have changed the apple. They
have made it decay. Organisms that make things
decay are called decomposers. Many different kinds of
microorganisms – including some kinds of bacteria and
microscopic fungi – are decomposers.
The spots on the apple are colonies of fungi.
Apples come from plants, which are living organisms.
Any substance that has been made by a living organism (by a plant or
animal) is called organic matter. So, apples are organic matter.
Some microorganisms can break down organic matter when they feed
on it. This is what has caused the apple to decay. The microscopic fungi
have broken down the crisp, fresh apple and made it become brown and
soft. They have made the apple rot.
Activity 7.3.1
What can microorganisms decay?
Here are three questions.
First, think quietly about the answers to the questions on your own.
When your teacher tells you to, turn to your partner and discuss your ideas.
Be ready to share your answers with the rest of the class.
Questions
1
Which of these things are made of organic matter?
bread water leather rock wood fruit
2
Think of two more things that are made of organic matter, and two more things that
are not made of organic matter.
3
Which of the things in your answers to Questions 1 and 2 can be broken down by
microorganisms?
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7 Microorganisms in the environment
Questions
1
Some microorganisms are decomposers. Explain what this means.
2
Describe one way in which decay by microorganisms is not useful.
3
Suggest one way in which decay by microorganisms is useful.
Think like a scientist
Investigating how temperature affects decay by microorganisms
Doing this investigation will give you practice in carefully collecting results and using
them to make a conclusion.
You will need:
• 2 similar pieces of bread
• 2 paper plates
• 2 plastic bags or some transparent food wrap
• a dropper pipette
1
Put two similar pieces of bread onto two
paper plates.
2
Add a little water to both pieces of bread.
Take care not to get them too wet.
3
Leave the bread open to the air for about
30 minutes. Then cover each plate with a
plastic bag or food wrap.
4
Put one plate in a warm place. Put the
other plate in a refrigerator.
5
Record the appearance of each piece of
bread each day, for several days.
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7.3 Microorganisms and decay
6
Continued
This bread has several patches of blue mould
growing on it.
This is what bread mould looks like through a microscope.
You can see the tiny threads that it is made of.
Questions
1
Compare the results for the bread in the warm place and the bread in the cold place.
2
Did other people in your class get similar results? If they were not the same, suggest
possible reasons for the differences.
3
Make a conclusion from the results of your investigation.
Self-assessment
1
For each of these statements about your experiment, decide whether you did it
very well, fairly well or not at all:
•
I was careful to add the same amount of water to each piece of bread.
•
I made a careful record of the appearance of each piece of bread
each day.
•
I wrote down or drew my results clearly, so that someone else could
understand them.
•
I made my conclusion from my actual results, not from what I thought
should happen.
2
Write down one thing that you did really well.
3
Choose one thing that you think you could do better next time, and explain how
you will try to improve it.
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7 Microorganisms in the environment
Think like a scientist
Investigating how moisture (water) affects decay
You are going to plan your own experiment. You can use ideas from the investigation
about how temperature affects decay by microorganisms.
Plan an experiment that you could do to test this hypothesis:
Moist bread decays more quickly than dry bread
Think about:
•
the variable you will change, and how you will do this
•
the variable you will observe or measure, and how you will do this
•
the variables you will keep the same
•
the results you predict you will obtain if the hypothesis is correct.
You may be able to do your experiment. If you can, collect results and use them to
make a conclusion.
Summary checklist
I can explain how microorganisms make things decay.
I can explain what a decomposer is.
I can use the results of my experiment to make a conclusion.
I can decide which variables to change, measure and keep the
same in an experiment.
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7.4 Microorganisms in food webs
7.4 Microorganisms in
food webs
In this topic you will:
•
draw and interpret food webs that include microorganisms
as decomposers
•
think about how microorganisms contribute to food webs.
Getting started
Key words
With a partner, discuss whether each of these statements
is correct.
dung
nutrients
1
The arrows in a food chain show the direction in which
energy flows from one organism to another.
2
All animals are consumers, and all plants are producers.
3
Some consumers are herbivores and some are carnivores.
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7 Microorganisms in the environment
Roles of decomposers
No-one would want to eat a rotten apple. The microorganisms that
make an apple decay have spoiled the food.
But most of the time, decay by microorganisms is useful.
Microorganisms break down dead bodies and animal waste. They
decompose this material. Almost all decomposers are microorganisms.
Fungi and bacteria are the most important decomposers.
If the dead bodies and waste are not broken down by decomposers, they
would just build up. There would be heaps of dead plants, dead animals
and animal dung everywhere.
But there is an even more important reason why decomposers are useful.
The dead bodies and waste contain substances that living organisms
can use to supply them with energy, or to help them to grow. These
substances are called nutrients.
When microorganisms decay organic matter, they return the nutrients to
the soil. Plants can then use the nutrients to help them to grow. This is
really helpful for the plants.
This also helps animals, because there are more plants to eat.
This fungus is a decomposer. It is breaking down the elephant dung.
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7.4 Microorganisms in food webs
Activity 7.4.1
Decomposing fruit
You will need:
•
a piece of fruit, such as a lemon or strawberry
•
a plate or dish to put the fruit onto
•
a pen to write on the plate or dish
Query log: Can we write on a plate
with a pen? Suggest they use pen,
paper and sellotape, or a pen and
sticky note.
Tech-Set: Please advise as query
log has no comments in
1
Write your name on a dish. Put the fruit onto the dish. Do not cover the fruit.
2
Leave the fruit in the laboratory, or another warm place.
3
Look at the fruit every two or three days. Take digital photographs of the fruit, or make
drawings of it.
Questions
1
What changes can you see in the fruit?
2
Explain what happens to the fruit.
What sort of decomposers are growing on these oranges?
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7 Microorganisms in the environment
Decomposers in food webs
Decomposers feed on almost every organism after it dies. They also
feed on waste from animals. This is how decay microorganisms get their
energy. Energy from the dead organisms and their waste is transferred to
the decomposers.
You can show this by adding decomposers to food chains or food webs.
You do not usually do this because you have to draw an arrow from
every organism in the food chain or food web to the decomposers. This
makes it look very complicated. The diagram shows a simple food web
with decomposers added to it.
python
fruit bat
parrot
microorganisms
banana
Questions
1
Write a food chain of your own. Add decomposers to your food
chain.
2
Look at the food web above. Are decomposers producers or
consumers? Explain your answer.
Activity 7.4.2
Are all decomposers microorganisms?
In this activity, you will think about how fungi fit into
food chains.
Look at the photograph.
The toadstools in the photograph are not
microorganisms. You can see them easily, without a
microscope.
In the photograph, the part of the fungus that you
cannot see is inside the log, breaking it down.
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7.4 Microorganisms in food webs
Activity 7.4.3
Questions
In a group of three, discuss these questions about the photograph. Be ready to share your
ideas with the rest of the class.
1
Is this fungus a decomposer? Explain your answer.
2
Is this fungus a microorganism? Explain your answer.
3
A slug eats the fungus. Explain where the energy obtained by the slug originally
came from.
4
Draw a food chain that describes your answer to question 3.
5
Apart from fungi, what other kinds of microorganisms act as decomposers?
Activity 7.4.4
Making a mind map
On a large sheet of paper, construct a mind map to link ideas about food webs,
microorganisms and decay.
Compare your mind map with a partner’s mind map. Ask your partner to explain their
mind map to you. Then explain your mind map to them.
Are there any similarities between the mind maps? What are the differences? Do you think
one is better than the other? If so, why do you think that?
Which is better for helping you to understand what you have
learned in this unit – making your own mind map, or looking at
someone else’s? Why do you think that?
Summary checklist
I can draw a food chain or food web including decomposers.
I can explain why microorganisms are important in food chains and
food webs.
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7 Microorganisms in the environment
Project: DDT and malaria
Most microorganisms are not harmful. But some microorganisms cause disease.
Malaria is a serious disease that is caused by a microscopic protozoan.
The microorganism that causes malaria is spread by mosquitoes. In some countries,
a chemical called DDT is used to kill mosquitoes. This reduces the number of cases
of malaria.
Unfortunately, DDT harms other animals as well as mosquitoes.
•
The World Health Organization, WHO, thinks we need to carry on using DDT until
better alternatives are found, to save thousands of human lives.
•
The Worldwide Fund for Nature, WWF, thinks we need to stop using DDT as soon
as possible, to protect the environment.
Work in a group of three or four. You are going to pretend that you represent the WHO
or the WWF. Your task is to put together a case to support your point of view. You will
then use your ideas in a debate about the different points of view.
You can use the information on these pages. You may also want to look for other
information on the internet. When you do this:
•
think carefully about who has produced the web pages you are looking at, and
decide whether you can trust the information to be unbiased
•
decide how relevant the information is to this task and use only the most
relevant information.
DDT and food chains
DDT does not break down completely in
an animal’s body. When an animal eats
another animal that has DDT in its body,
it also eats the DDT. If an animal moves
from one place to another, it takes the
DDT with it.
DDT effects on animals
DDT is very poisonous to fish, and quite
poisonous for frogs and other amphibians.
We are not sure yet how poisonous DDT
is to humans.
Midway Atoll, where this black-footed albatross lives, is
thousands of miles from any land where DDT is used. But
DDT has been found in the albatrosses there.
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7.4 Microorganisms in food webs
DDT and birds of prey
DDT in birds of prey makes the shells
of their eggs very thin. The eggs break
before the young birds hatch. In the
USA, numbers of bald eagles fell
when DDT was used. DDT was
banned in 1972.
Average number of young per breeding area
Continued
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1966 1968 1970 1972 1974 1976 1978 1980 1982
Year
DDT ban
Indoor residual spraying
In many countries where malaria is
present, DDT is sprayed inside
houses. The DDT sticks to the walls and
kills mosquitoes. The DDT continues to
work for up to 6 months. This method
needs much less DDT to control
mosquitoes than spraying it outside.
Deaths from malaria
In 2015, 212 million people had malaria. 429 000 people died from it. In 2016, there were
216 million cases and 445 000 deaths.
More than two-thirds of people dying from malaria are children under the age of 5.
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7 Microorganisms in the environment
Continued
Where is malaria present?
Malaria occurs where the mosquitoes that transmit it live. These mosquitoes only live in
tropical or subtropical countries.
Key
Area with
no malaria
Area with
malaria
Malaria and global warming
The Earth's mean temperature is increasing. This may mean that the mosquitoes that
transmit malaria may be able to move into new areas.
Other methods of controlling malaria
Other chemicals can be used to kill mosquitoes. However, most of these are much more
expensive than DDT.
Sleeping under a bed net can help to reduce the risk of being bitten by a mosquito.
A malaria vaccine?
Scientists are trying to make a vaccine for malaria. The best one they have found so far
needs four injections. It only halves the risk of getting malaria.
DDT persistence
DDT is a persistent chemical. This means that it lasts for a long time. If DDT gets into a
lake or river, over half of the DDT will still be there 150 years later.
Where is DDT used?
DDT has been completely banned in 34 countries. Many countries, including India and
many African countries, still use DDT.
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Woukd be good if we can use this
image across both pages in the
spread.
Tech-Set: Please advise
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7 Microorganisms in the environment
Check your Progress
7.1 Yeast is a single-celled organism that grows on fruit, such as grapes. Yeast feeds on
sugar in the grapes. It breaks down the grapes and makes them rot.
[2]
Which sentences about yeast are correct?
A
Yeast is a producer.
B
Yeast is a decomposer.
C
Yeast is a microorganism.
D
Yeast is a virus.
7.2 Draw a food chain that includes
microorganisms as decomposers.
You do not need to draw pictures
– just write the names.
[2]
7.3 A farmer keeps cattle in a field of grass.
The cattle leave dung in the field. Fungi grow
on the dung. The farmer notices that the grass
looks greener, and grows taller, when it grows
next to cow dung.
The farmer measures the length of five grass
leaves close to some cow dung, and another
five grass leaves where there is no cow dung.
Here are her results.
Next to cow dung: 11 cm, 13 cm, 9 cm, 12 cm, 8 cm
No cow dung: 9 cm, 10 cm, 6 cm, 7 cm, 9 cm
a
Record the farmer's results in a suitable results table.
[4]
b
Calculate the mean length of the grass leaves next to cow dung.
Then calculate the mean length where there is no cow dung. Write the
mean lengths in your results table.
[2]
The farmer concludes that grass grows longer next to cow dung. Do you
think she has enough evidence to make this conclusion? Explain your answer.
[3]
Explain how the fungi and cow dung might help the grass to grow better.
[2]
c
d
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7 Microorganisms in the environment
7.4 Some bacteria are decomposers. They break down food and change it. Usually this
makes the food unpleasant, but sometimes it changes it to something that is good to eat.
One kind of bacterium changes milk to yoghurt. When the bacteria do this, they
change sugar in the milk to acid. Many people like the sharp taste that the acid
provides.
Sofia makes some yoghurt.
•
She washes out a plastic container with boiling water.
•
She lets the pot cool down, then puts some fresh milk into the container.
•
She adds a small spoonful of yoghurt she bought.
•
She covers the container with cling film.
•
She puts the container in the refrigerator.
S of ia’s
’
Yoghur t
live
YOGHURT
S of ia’s
Yoghur t
a
Explain why it is a good idea to wash the container with boiling water.
[1]
b
Suggest what is in the yoghurt that Sofia bought, that helps to turn her
fresh milk into yoghurt.
[1]
c
It takes a long time for Sofia’s milk to turn into yoghurt.
Suggest what she can do to make it happen faster.
[2]
Explain your answer.
d
Sofia measures the pH of the milk before she puts it into the pot.
She measures it again after it had been in the pot for four days.
Suggest how the pH changes. Choose from:
becomes higher becomes lower stays the same
[2]
Explain your answer.
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8
Changes to
materials
8.1 Simple chemical reactions
In this topic you will:
•
learn about the chemical properties of some metals
•
learn to recognise that a chemical reaction has taken place.
Getting started
Key words
Draw each of these hazard symbols and write down the scientific
word for:
chemical reaction
combine
productreact
reactant
•
a substance that can poison you
•
a substance that catches fire easily
•
a substance that can dissolve your skin.
Check your answers with a partner. Be prepared to share them
with the class.
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8 Changes to materials
Chemical and physical properties
The physical properties of a substance are features such as:
•
what colour it is
•
if it is a solid, liquid or a gas
•
what its boiling or melting temperature is
•
if it is heavy or light.
For example, some of the physical properties of iron are that it is a
grey, heavy solid with a melting point of 1538 °C. One of the physical
properties of hydrochloric acid is that it is a colourless liquid.
The chemical properties of a substance are features such as:
•
how acidic or alkaline it is
•
how it reacts with water, acids or metals
•
how readily it reacts.
Some of the chemical properties of iron are that it combines with sulfur
when heated to form iron sulfide, and it combines with oxygen to form
iron oxide or rust. One of the chemical properties of hydrochloric acid is
that it is has a pH of 2.
Chemical changes
Chemical changes are different from physical changes.
In a physical change, no new substances are formed. For example, when
liquid water freezes, the water has changed state but it is still the same
substance after the change.
In a chemical change, new substances are formed. For example,
when iron and sulfur are heated together, they form a new substance
(a compound called iron sulfide).
iron
+
sulfur
iron sulfide
The iron and the sulfur have reacted together to form a new substance.
A chemical reaction has taken place. The iron atoms have combined and
bonded with the sulfur atoms.
The reactants (the substances that react together) are the iron and the
sulfur. The products are the new substances made in the reaction. In this
reaction, there is only one product – iron sulfide.
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8.1 Simple chemical reactions
In some chemical reactions, a substance breaks apart to make new
substances. For example, water can be split apart to form oxygen and
hydrogen.
water
oxygen
+
hydrogen
Chemical reactions happen everywhere. They happen inside plants when
they grow and when they decay. Chemical reactions happen inside your
body to keep you alive, for example, when you digest food.
Burning
Burning is a chemical reaction. When a substance burns, the
substance reacts with the oxygen in the air. Sometimes ashes
are formed. The ashes contain new substances. The new
substances in the ashes are oxides.
Charcoal is made up of the element carbon. When carbon
burns it combines with oxygen in the air to make the gas
carbon dioxide.
carbon
oxygen
+
carbon dioxide
When charcoal burns, ash is left behind.
When magnesium metal is burnt, a white powder is formed. This powder
is magnesium oxide. A new substance has been formed from magnesium
and oxygen.
Magnesium and oxygen are the reactants. Magnesium oxide is the
product. A chemical property of magnesium is that it burns in air to
form magnesium oxide by combining with oxygen.
magnesium
oxygen
+
magnesium oxide
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8 Changes to materials
Think like a scientist
Burning magnesium
In this task you will burn some magnesium and produce a new product.
You will need:
• safety glasses
• a Bunsen burner
• a heat-proof mat
• tongs
• a piece of magnesium ribbon
Safety
Wear safety glasses. While the magnesium ribbon is burning, do not look directly
at the flame. Magnesium burns very brightly and the bright light could harm
your eyes.
1
Set up the Bunsen burner on the heat-proof mat.
2
Take a small piece of magnesium ribbon and place it in the tongs.
3
Hold the tongs at arm‘s length and place the magnesium ribbon in the Bunsen flame.
4
Once the magnesium ribbon has caught fire, remove it from the flame.
Magnesium ribbon
Burning magnesium ribbon
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Magnesium oxide
8.1 Simple chemical reactions
Continued
Questions
1
Describe what happens to the magnesium ribbon.
2
Describe what has been formed.
3
Name the reactants in this chemical reaction.
4
List all the safety precautions you need to take while carrying out this experiment.
Not all metals have the same chemical properties as magnesium. They may not burn in
the same way. You could try holding pieces of other metals, such as copper, zinc or iron, in
the Bunsen flame and record what happens.
Properties of reactants and products
This table compares the properties of the reactants and products when
you burn magnesium. You can see that the properties of the product are
different from those of the reactants.
Reactants
Product
magnesium
oxygen
magnesium
oxide
Element or
compound?
element
element
compound
State at room
temperature
solid
gas
solid
Appearance
soft, shiny,
malleable
colourless, has
no smell
white,
powdery
Conducts
electricity?
yes
no
no
Melting
point in °C
651
– 214
2800
Questions
1
Compare the melting points of magnesium, oxygen and
magnesium oxide.
2
Find one similarity between magnesium oxide and one of
the reactants.
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8 Changes to materials
3
For each of these photographs, say if it is a physical change or a
chemical reaction, and explain why you think so.
a Making toast
b Melting chocolate c Fireworks going off
d Ice melting
e Coal burning
f Copper roof
turning green
Reactions with water
Some substances react very violently with water. Some
substances do not react with water at all.
Potassium (a metal) is very soft and can be cut with a knife.
This is a physical property. Potassium is so reactive that it
has to be stored under oil to prevent it reacting with the
water vapour in the air. This is a chemical property.
When a very small piece of potassium is placed in a large
trough of water, hydrogen gas is given off. The reaction
produces so much heat that the gas burns.
Potassium reacting with water in a large
glass trough
Safety
You cannot carry out the potassium and water reaction yourself.
If your teacher shows it to you as a demonstration, you must wear
safety glasses and there must be a safety screen in front of the
beaker to protect you.
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8.1 Simple chemical reactions
Reactions with acid
When magnesium is placed in hydrochloric acid, bubbles of gas
are given off. The magnesium has reacted with the hydrochloric
acid and formed new substances. The gas is hydrogen, and
magnesium chloride has been formed. This is a chemical
property of magnesium.
magnesium + hydrochloric acid
magnesium chloride + hydrogen
When you see bubbles forming in a reaction, you know that a
gas is being produced. But you cannot tell what type of gas it is.
The diagrams show you how to test a gas to find out if it is
hydrogen. Hydrogen gas burns with a squeaky pop. To carry
out the test you light a splint and place it in the mouth of the
test tube. You need to keep your finger over the end of the test
tube until the last moment or you will have no hydrogen left to
test. This is because hydrogen gas is lighter than air.
Magnesium in acid
When the hydrogen pops, it is reacting with oxygen, in the air, to
form water.
hydrochloric acid
magnesium
pop
splint
Hydrogen can be produced on a larger scale by collecting the gas
produced in the reaction over water, as shown in this diagram.
You could try this for yourself.
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8 Changes to materials
acid
delivery tube
thistle funnel
measuring
cylinder
glass
lid
hydrogen
gas
bee-hive shelf
water
conical flask
metal
acid
Think like a scientist
Reactions with water and acid
You will need:
• safety glasses
• test tubes
• a test tube rack • water
• hydrochloric acid
• small pieces of a selection of metals such as magnesium, iron, copper, zinc
Safety
Wear safety glasses. Remember to pay attention to hazard warning labels when you
use chemicals.
Part 1: Reactions with water
1
Place a small piece of each of the metals into a different test tube.
2
Take one tube at a time and add water, so that the test tube is half full.
3
Record your observations and findings in a table.
Part 2: Reactions with acid
1
Place a small piece of each of the metals into a different test tube.
2
Take one tube at a time and add hydrochloric acid, so that the test tube is half full.
3
If you see bubbles given off, test for hydrogen gas.
4
Record your observations and findings in a table.
5
For each reaction with acid, write down the reactants and the products.
6
What safety precautions did you take?
7
Explain how you tested for hydrogen.
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8.1 Simple chemical reactions
Comment on any difficulties you had testing for hydrogen and
how you tried to overcome them. What have you found out
about the chemical properties of the metals you tested?
Questions
4
Give two of the chemical properties of magnesium.
5
Give two of the physical properties of magnesium.
6
What are the products when zinc reacts with hydrochloric acid?
Summary checklist
I can describe some of the chemical properties of some metals.
I can recognise that a chemical reaction has taken place.
I can test a gas to see if it is hydrogen.
Tech-Set: Maybe an incidental
image could be used here
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8 Changes to materials
8.2 Neutralisation
In this topic you will:
•
learn how to make a neutral solution
•
learn why neutralisation is important.
Getting started
Key words
What does the word ‘neutral’ mean? Discuss with a partner all
you know about the properties of a neutral liquid. How can you
tell if the liquid you have is neutral?
burette
decay
digest
filtrate
indigestion
neutralisation
neutralised
Be prepared to share your ideas with the class.
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8.2 Neutralisation
Mixing acids and alkalis
Acids and alkalis can cancel each other out. When you mix them
together they react and make a neutral solution. This is called
neutralisation. This is another chemical change. Neutrality is also a
chemical property of a substance.
If you add too much acid to an alkali, it makes an acidic liquid.
If you add too little acid to an alkali, it stays as an alkaline liquid.
You can add the acid very slowly, adding a few drops at a time.
This makes it easier to judge exactly when it becomes neutral.
acid
alkali
neutral
Mixing acid and alkali to make a neutral solution.
Questions
1
What colour is universal indicator when the solution is neutral?
2
What sort of reaction happens when an acid and an alkali are
mixed?
Making a neutral solution
You can use a special piece of equipment called a burette to neutralise
an alkali very accurately. You add universal indicator to the alkali in
the flask.
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8 Changes to materials
0 cm3
burette
25 cm3
28 cm3
acid
50 cm3
50 cm3
50 cm3
conical flask
alkali and universal indicator
Using a burette to add acid to a flask of alkali.
Look at the three diagrams of a burette.
In the first diagram, the pH in the flask is about 13. As the acid is added,
the pH becomes lower. The acid is added slowly. The flask is shaken
each time some acid is added.
In the second diagram, 25 cm3 of acid has been added to the flask.
The pH in the flask is now 7. The liquid is now neutral.
The acid has reacted with the alkali and neutralised it.
In the third diagram, a little more acid has been added to the flask.
The pH in the flask is now about 6. The liquid is weakly acidic.
When this happens there is a chemical reaction and new substances are
formed. If you use hydrochloric acid and sodium hydroxide (an alkali),
these are the reactants. When they react together, the products that form
are sodium chloride and water.
hydrochloric acid
+
sodium hydroxide
sodium chloride
+
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water
8.2 Neutralisation
Activity 8.2.1
Rainbow neutralisation
In this activity you will demonstrate the different colours shown by universal indicator
solution.
You will need
The apparatus shown in the diagram.
Safety
Wear safety glasses.
1
Fix a test tube into a clamp stand and place it somewhere it will not get moved.
2
Place a crystal of washing soda in the bottom of a test tube.
3
Carefully add some water until the tube is about two-thirds full.
4
Add a few drops of universal indicator.
5
Carefully pour some acid on the top. Do not shake the tube.
6
Leave the tube to stand for a few days.
SEE QUERY LOG Zara should be
wearing a lab coat.
CUP to supply updated image,
please do not deliver revised proofs
until you've received it
universal indicator solution
Tech-Set: Please advise
hydrochloric acid
clamp stand
water
crystal of washing soda
Questions
1
What is the pH at the top part of the test tube?
2
What is the pH at the bottom of the test tube?
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8 Changes to materials
Continued
3
Which is the most alkaline part of the tube?
4
Why did you have to keep the tube still when you left it for a few days?
5
Which hazard symbols are displayed on the equipment you used? What do these
mean?
How does the rainbow appear?
At the top of the test tube
The acid has turned the universal indicator red at the top of
the tube. This shows it is strongly acidic. The acid particles
gradually move down the tube. They mix with more water
and the universal indicator turns yellow. This is more weakly
acidic.
In the middle of the test tube
The acid and the washing soda solution mix. They react
together. The universal indicator is yellow. The washing soda
solution and acid have neutralised each other.
At the bottom of the test tube
The washing soda has dissolved in the water around it. The
universal indicator is purple or dark blue around the washing
soda. The washing soda is a strong alkali. The particles of
the washing soda gradually move up the test tube. They mix
with more water and the universal indicator turns a lighter
blue. This shows it is more weakly alkaline.
The rainbow neutralisation
experiment after a few days.
Self-assessment
How successful was your rainbow? Was there anything you could have done to improve
the outcome?
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8.2 Neutralisation
Neutralisation in everyday life
Indigestion
Your stomach produces hydrochloric acid. This acid gives the stomach
the right conditions to digest your food. When your stomach produces
too much acid, you have indigestion. It can be very uncomfortable.
There are many medicines that can help. They are all alkalis and they
neutralise the acid. Sometimes these medicines are called antacids.
Antacid medicines for indigestion
Toothpaste
There are millions of bacteria in your mouth. These bacteria
feed on the pieces of food left on your teeth. The bacteria
produce acid when they feed. This acid damages your teeth
and makes them decay. Toothpaste contains alkali and this
helps to neutralise the acid.
Toothpaste helps to neutralise the
acid in your mouth.
Neutralising lakes
In some parts of the world there are harmful chemicals in the air
that make the rain acidic. This acid rain damages trees and changes
the pH of the lakes, rivers and ponds. The plants and animals that
live in the lakes cannot live in acid conditions. Some countries drop
alkalis into the lakes to neutralise the acid.
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8 Changes to materials
Growing crops
In some areas, the soil is very acidic and plants do not
grow well. Farmers spread lime on the soil to neutralise
the acid so that the plants can grow better.
Questions
3
Why is toothpaste alkaline?
4
Where does the acid in your mouth come from?
5
Why is an alkaline substance dropped into lakes in
some countries?
6
What do farmers spread onto acidic soil?
Explain why they do this.
Lime is added to acidic soils, to neutralise the acid.
Think like a scientist
Testing the pH of the soil
In this task you will test a soil sample to find the pH.
You will need:
• 2 test tubes
• a beaker of water • a filter funnel
• filter paper
• universal indicator
• a sample of soil
1
Take a sample of soil in a test tube and add some water.
2
Shake the tube.
3
Filter the mixture in the tube.
4
Add a few drops of universal indicator to the filtrate. (The filtrate is the liquid that
comes through the filter paper.)
5
Record your results.
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8.2 Neutralisation
Continued
filter funnel
filter paper
universal
indicator
water
filtrate
1 Add water.
2 Shake.
3 Filter.
4 Test.
Question
Use books or the internet to find out what sort of plants will grow well in this type of soil.
Summary checklist
I can describe neutralisation as a change to a pH of 7.
I can explain how to make a neutral solution.
I can explain why neutralisation is important.
filler image needed Getty
129374971
Tech-Set: Please advise is this is
the correct image
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8 Changes to materials
8.3 Investigating acids and alkalis
In this topic you will:
•
discuss questions that you can test
•
plan an investigation
•
think about what the results of an investigation tell you.
SEE QUERY LOG
Author to rewrite this. We do not
test questions. We devise and carry
out tests to look for answers to
questions.
Tech-Set: Please advise as no
comments in the query log
Getting started
Key words
With a partner, write down the different colours of universal
indicator when it is added to solutions with different pH.
How good were you at remembering the colours and what
they mean?
remedy
variable
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8.3 Investigating acids and alkalis
Asking questions
Scientists ask questions. These are some questions about neutralisation
that scientists might try to answer.
•
How much lime should be added to an acid lake to neutralise it?
•
Which is the best indigestion remedy (treatment for an illness
or injury)?
•
How much toothpaste is needed to neutralise the acid in your mouth?
Let’s look at the second question: ‘Which is the best indigestion remedy?’
It is not a very precise question. What does ‘best’ mean? Does ‘best’
mean the most pleasant tasting, the cheapest, the most effective or the
most cost-effective?
Scientists need to write their question in a way that they can test. So,
instead of asking: ‘Which is the best indigestion remedy?’, a scientist
might ask:
•
‘Which indigestion powder neutralises the acid, using the least
amount of powder?’
Think like a scientist
Asking questions
In a group of three or four, discuss and write down four questions about acids and alkalis
that you could investigate.
Share your ideas with the rest of the class.
Could each of your questions be investigated?
Planning an investigation
When you plan to do an investigation, you have to design an experiment.
If you are investigating the effect of indigestion powders on stomach
acid, you cannot use your own stomach acid. You have to use a model
instead, such as a beaker of acid.
There is a lot to think about.
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8 Changes to materials
How will I make
my test fair?
What will
I measure?
What will I do
to stay safe?
What equipment
do I need?
What will I change
in the investigation
and what will I keep
the same?
The things that change are called variables.
•
How will you know when the powder has neutralised the acid?
•
What will you see happen?
•
How will you carry out the investigation?
•
How will you record the results?
Think like a scientist
Planning an investigation
Working in the same group as before, choose one of the questions from Think like a
scientist: Asking questions.
In your group, plan how you could carry out the investigation.
When you have discussed it in your group, divide up the tasks. These might include
‘equipment list’, ‘method’, ‘safety’, ‘results table’ and so on.
Each group member should produce something to put onto a large piece of paper and
share with the class.
You may be able to carry out your investigation, once it has been checked for safety.
Self-assessment
How well did your group do? Was your plan safe? Would your plan work? Was the test fair?
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8.3 Investigating acids and alkalis
Which powder is best at
neutralising acid?
Marcus and Arun put 20 cm3 of hydrochloric acid into each of three
beakers. The acid has a pH of 1. This is like the strong acid in your
stomach. They also put a few drops of universal indicator in each beaker.
They add the indigestion powder, spatula by spatula, until the acid is
neutralised and the universal indicator is green. They do this with each
of the three powders A, B and C. They record the number of spatulas
they used.
spatula
indigestion
powder
hydrochloric acid and
universal indicator
Here are Marcus and Arun’s results.
Powder
Number of spatulas used to neutralise the acid
A
10
B
6
C
24
Questions
1
Marcus and Arun are using acid that is pH 1. What should they do
to stay safe?
2
Which variables are they keeping the same in this investigation?
3
Which variable is being changed?
4
What is being measured?
5
Which is the most effective powder?
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8 Changes to materials
6
Which is the least effective powder?
7
Do you think there is enough evidence to be certain of your answers
to questions 5 and 6?
Marcus and Arun repeat their investigation twice more. The table shows
all their results.
Powder
Number of spatulas used to neutralise the acid
First try
Second try
Third try
Mean
A
10
9
11
10
B
6
17
16
13
C
24
23
25
24
8
Now which powder do you think is the most effective?
9
Which result looks ‘wrong’?
10 Suggest why Marcus and Arun might have got this ‘wrong’ result.
11 What should they have done about it?
12 Should they have included the ‘wrong’ result when working out
the mean?
What do the three sets of results tell you about carrying out
an investigation? When you see evidence from someone else’s
investigation, what do you need to ask?
Summary checklist
I can word a question so that it can be tested.
I can plan an investigation.
I can look critically at what the results of an investigation tell me.
SEE QUERY LOG
Again, we do not test
questions. We devise
and carry out tests to
look for answers to
questions. Author to
rephrase this.
Tech-Set: Please advise
as no comments in the
query log
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8.4 Detecting chemical reactions
8.4 Detecting chemical reactions
In this topic you will:
•
learn about different ways of telling if a chemical reaction
has happened
•
test gases given off in reactions so that you can identify them
•
carry out practical tasks safely.
Getting started
Key words
What is the difference between:
cloudy
glowing
precipitate
•
reactants and products
•
chemical and physical changes
•
acids and alkalis?
Think about these three questions for a minute, then spend
one minute writing your answers. Compare your answers with a
partner. Take two minutes to improve your answers. Be prepared
to share your answers with the class.
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8 Changes to materials
What happens in a chemical reaction
In a chemical reaction, new products are formed from the reactants.
How can you tell this has happened? There are some clues you can look
out for that might mean a reaction has taken place.
A gas is given off
One of the most useful clues to help decide if a chemical reaction has
taken place is whether a gas is given off. Consider these three reactions.
Reaction 1
You have seen the reaction of magnesium with acid and seen bubbles
of the gas hydrogen given off in Topic 8.1. You learnt how to test
for hydrogen.
Magnesium reacting with hydrochloric acid
magnesium + hydrochloric acid
magnesium chloride + hydrogen
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8.4 Detecting chemical reactions
Reaction 2
When baking powder and vinegar react, a gas is also given off. This gas
is carbon dioxide. You can test for carbon dioxide by using limewater.
When limewater mixes with the carbon dioxide, the limewater turns
cloudy.
Limewater turns cloudy when carbon dioxide is bubbled through it.
Reaction 3
When a piece of apple is placed in hydrogen peroxide it bubbles. A gas is
given off. This gas is oxygen. To test for oxygen you use a glowing splint.
When the glowing splint is placed in the mouth of the test tube, it will
relight if the gas is oxygen.
hydrogen peroxide
piece of apple
When hydrogen peroxide and the chemicals in the apple react, oxygen is given off.
Oxygen will relight a glowing splint.
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8 Changes to materials
Activity 8.4.1
Testing gases
Try these reactions and test the gas that is given off.
You will need:
The apparatus shown in the diagrams
Safety
Wear safety glasses.
Testing for carbon dioxide
1
Pour limewater into a test tube until it is about half full.
2
Place a small amount of calcium carbonate into another test tube.
3
Add some hydrochloric acid to the calcium carbonate in the test tube.
4
Quickly fit the rubber bung and delivery tube.
5
Ensure the delivery tube reaches into the limewater.
delivery tube
SEE QUERY LOG
He should he be
wearing a lab coat.
CUP to supply updated
image, please do not
deliver revised proofs
until you've received it
rubber bung
calcium carbonate
and
hydrochloric acid
Tech-Set: Awaiting new
artwork
limewater
test tube
Testing for oxygen
1
Pour hydrogen peroxide into a test tube until it is about
half full.
2
Add a spatula of manganese dioxide.
3
Place a glowing splint into the neck of the test tube.
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8.4 Detecting chemical reactions
Continued
manganese dioxide
xid
de
hydrogen peroxide
Questions
1
Describe the changes to the limewater when you tested for carbon dioxide.
2
Describe what happened to the glowing splint when you tested for oxygen.
How easy was it to carry out the tests for gases? What difficulties
did you have? How did you attempt to overcome them?
Other chemical reaction clues
Reactant ‘disappears’
When magnesium ribbon reacts with acid, hydrogen is produced and
the magnesium ribbon ‘disappears’. The magnesium is used up in the
reaction; it combines with the chlorine from the hydrochloric acid to
form magnesium chloride.
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8 Changes to materials
Colour change
Gently heating black copper oxide with sulfuric
acid produces a blue solution of copper sulfate.
copper oxide (black) + sulfuric acid → copper sulfare + water
Safety
If you try this in the laboratory, make sure
you do not boil the blue liquid, as harmful
fumes will be given off.
Heat is produced
copper oxide + sulfuric acid
(black)
copper sulfate + water
(blue)
When potassium is placed in water, hydrogen
gas is given off. The reaction produces so much
heat the hydrogen burns.
Safety
This reaction should only be done by a teacher.
When you added zinc to hydrochloric acid,
hydrogen gas was given off and the test tube
felt hot.
hydrochloric acid
Change in pH
When you neutralise an alkali, there is a change
in pH. It is called a neutralisation reaction.
sodium hydroxide + hydrochloric acid → sodium chloride + water
sodium hydroxide
In this reaction, sodium chloride
and water are produced.
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8.4 Detecting chemical reactions
A precipitate is formed
If you mix solutions of silver nitrate and calcium chloride, a chemical
reaction takes place. When the two solutions (liquids) are mixed, a solid
is formed. This solid is called a precipitate. In this example, the solid is
silver chloride.
silver nitrate + calcium chloride → silver chloride + calcium nitrate
When silver nitrate and calcium chloride
react, a precipitate is formed.
As carbon dioxide is bubbled into limewater, a precipitate is formed.
When you tested for carbon dioxide gas, you used limewater.
Limewater is a solution of calcium hydroxide. You saw that the
limewater turned cloudy when carbon dioxide was bubbled into it. This
is because a precipitate of calcium carbonate formed. You added a gas
to a liquid, and a solid was formed.
calcium hydroxide + carbon dioxide → calcium carbonate + water
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8 Changes to materials
Think like a scientist
Chemical reactions or not?
A series of experiments will be set up in the laboratory. You will be told which ones to carry out.
Safety
Before trying any of these reactions, you must carry out a risk assessment. Think about
how you will stay safe.
Try some or all of these activities and decide if a chemical reaction has taken place. Share
them with the class.
You do not need to carry out these investigations in any particular order.
For each investigation, state what you did and mention any safety considerations. What
clues help you to decide?
Experiment A
Experiment B
You will need:
You will need:
• safety glasses • black copper oxide
powder • dilute sulfuric acid
• a beaker and a stirring rod
• safety glasses • a test tube
• a test tube rack • a small piece
of zinc • dilute hydrochloric acid
• a beaker and a stirring rod
Add some black copper oxide powder
to about 150 cm3 dilute sulfuric acid in a
beaker. Stir gently.
Half-fill a test tube with dilute hydrochloric
acid. Add a small piece of zinc.
What do you observe? Has a chemical
reaction taken place? What evidence do
you have?
What do you observe? Has a chemical reaction
taken place? What evidence do you have?
Experiment C
Experiment D
When you hold the test tube in your hands,
do you notice anything?
You will need:
You will need:
• safety glasses • limewater • a test
tube • test tube rack • a straw
• safety glasses • a piece of chocolate
• test tube • test tube rack
• a beaker • access to hot water
Half-fill a test tube with limewater. Use the
straw and blow gently into it.
Fill a beaker with hot water. Place a small
piece of chocolate in a test tube. Stand the
What do you observe? Has a chemical
test tube in the beaker of hot water.
reaction taken place? What evidence do
you have?
What do you observe? Has a chemical reaction
taken place? What evidence do you have?
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8.4 Detecting chemical reactions
Continued
Experiment E
Experiment F
You will need:
You will need:
• safety glasses • copper sulfate
solution • evaporating dish
• pipe-clay triangle • tripod
• Bunsen burner • tongs
• safety glasses • sodium hydroxide
• conical flask • measuring cylinder
• universal indicator • hydrochloric
acid • burette
Place a solution of copper sulfate in an
evaporating dish. Heat gently until the
solution starts to spit. Turn off the heat
and leave the evaporating basin to cool.
What do you observe? Has a chemical
reaction taken place? What evidence do
you have?
Experiment G
Place of sodium hydroxide in a conical
flask and add a few drops of universal
indicator solution. Add acid slowly from
a burette until the universal indicator
changes to green.
What do you observe? Has a chemical
reaction taken place? What evidence do
you have?
Experiment H
You will need:
You will need:
• safety glasses • baking powder
• spatula • vinegar • test tube
• test tube rack
• safety glasses • test tube • test
tube rack • solution of silver nitrate
• solution of calcium chloride
Put a few spatulas of baking powder in a
test tube. Add vinegar.
Place silver nitrate in the test tube, about half
full. Add calcium chloride solution slowly.
What do you observe? Has a chemical
reaction taken place? What evidence do
you have?
What do you observe? Has a chemical
reaction taken place? What evidence do
you have?
What clues helped you to decide if a chemical reaction had taken place?
Summary checklist
I can list different ways of identifying that a chemical reaction has
taken place.
I can test gases for hydrogen, oxygen and carbon dioxide.
I can carry out practical work safely.
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8 Changes to materials
Project: Moving dangerous chemicals
Acids and alkalis need to be moved from where they are produced to where they are
used. This can be very dangerous if there are spills and accidents.
Work in a group of three. You are a team of reporters who are going to write a report
about a serious accident that has happened on a major road. The accident involved a
truck carrying concentrated acid. The emergency services attended the accident and dealt
with the spill of acid.
Here is a list of some things you could consider.
•
Why is an acid spill so dangerous?
•
What would happen if people drove their cars through the acid spill?
•
How do the emergency services know which chemical they are dealing with?
•
What must the emergency services do to the spilt acid?
•
How will they know when the task is complete?
•
What safety measures must be taken by the emergency services to deal with the spill?
•
What would be the effect of the acid reaching the soil alongside the road?
•
What regulations are in place in your area about the transport of dangerous materials?
•
What considerations are there for moving dangerous chemicals by sea or air?
Decide which of you will research each of the suggestions above. Set a time limit and then
meet to share your findings. You may need to do further research or discover other areas
you want to find out about.
Your report could be written as if it is for a newspaper or magazine. It could be in the form
of a radio or television interview or a presentation to the class. Choose a form that you
have not used in another science project.
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8 Changes to materials
Check your Progress
8.1 Draw a table to sort the following list into either physical change or chemical reaction. [5]
•
burning a piece of wood
•
melting chocolate
•
cooking an egg
•
heating glass and bending it
•
baking a cake
8.2 The diagram shows an experiment where zinc metal is added to
sulfuric acid.
a
What is the name of the gas given off in this reaction? [1]
b
How do you test for this gas?
[2]
c
What products are formed in this reaction?
[2]
d
How do you know when all the acid has reacted?
[1]
8.3 Magnesium ribbon burns in air.
sulfuric acid
zinc
a
Write the chemical symbol for magnesium.
[1]
b
Name the element in the air that reacts with magnesium when it burns.
[1]
c
Name the compound formed when this element reacts with magnesium.
[1]
d
Magnesium also reacts with chlorine. Suggest the name of the product of
this reaction.
[1]
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8 Changes to materials
8.4 Look at these reactions.
A
Carbon combines with oxygen to form carbon dioxide.
B
Sodium hydroxide reacts with hydrochloric acid to produce sodium chloride
and water.
C
Potassium and water react to form potassium hydroxide and hydrogen.
D
Copper carbonate reacts to produce copper oxide and carbon dioxide.
Write the letter of the reaction that:
a
produces a metal oxide
[1]
b
is a neutralisation reaction
[1]
c
is a burning reaction.
[1]
8.5 Zara and Sofia put 50 cm3 of alkali into a conical flask. They added a few drops of
universal indicator to the alkali. They used a burette to add acid to the alkali. Zara
added the acid 10 cm3 at a time. Sofia stirred the contents of the conical flask each time
acid was added. They recorded the pH after each addition of acid.
The table shows their results.
Volume of acid added in cm3
0
10
20
30
40
50
pH of solution
12
11
10
9
8
7
burette
acid
alkali and
universal
indicator
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8 Changes to materials
a
What colour was the alkali and universal indicator solution at the start?
[1]
b
What colour was the solution in the flask at the end?
[1]
c
Which one of the statements is correct?
[1]
•
The acid was stronger than the alkali.
•
The alkali was stronger then the acid.
•
The acid and the alkali were equal in strength.
Explain your answer.
d
Draw a line graph of Zara and Sofia’s results on graph paper.
Place the pH on the vertical axis.
[4]
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9
Electricity
9.1 Flow of electricity
In this topic you will:
•
understand how electricity flows around a circuit
•
learn about the electrons that flow to make electric current.
Getting started
Key words
Work in groups to discuss answers to these questions.
attract
battery
cell
components
current
electrons
free to move
negative charge
repel
terminals
1
Which of these must be present in a complete circuit for
current to flow?
lamp
2
cell
switch
wire
Which of these flows around a complete circuit?
voltage
wires
current
heat
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9.1 Flow of electricity
Current
Look at the circuit in the picture.
When you close the switch, the lamp lights.
A cell stores chemical energy that can be
changed to electrical energy in a circuit.
A battery contains two or more cells
joined together.
cell
The cell in the circuit has two
connections, called terminals.
All cells, batteries, power supplies
and many other components have two
terminals.
The terminals are labelled with + and
− symbols, meaning positive (+) and
negative (−).
switch
lamp
What happens to make the lamp light?
You can see these symbols in the photograph of these
three cells.
The photograph below shows one of the batteries from an
electric car. You can see that the battery is made from many cells.
When connected into a circuit, the negative terminal of a cell,
battery or power supply pushes electrons around in the wires.
All materials contain atoms. Atoms contain smaller particles.
An electron is one type of smaller particle in an atom.
The flow of electrons in the circuit is called current.
The + and – symbols on these cells show
the positive and negative terminals.
flow of
electrons
This battery pack from an electric car is made from
hundreds of separate cells connected together.
The flow of current in a circuit is the movement of electrons
around the circuit.
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9 Electricity
More about electrons
Some of the electrons in a metal are free to move. That means they can
move through the metal.
In a metal, these electrons move randomly, as shown in the diagram.
Electrons are very small and this diagram is not to scale.
When the metal is placed into a circuit, the electrons move in the
same direction.
metal
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
electrons
−
−
−
+
−
−
−
−
−
−
−
−
Electrons in a metal move randomly.
−
−
−
−
−
•
positive and positive repel
•
negative and negative repel.
Therefore, electrons will be attracted towards the positive terminal of
the power supply and be repelled from the negative terminal.
If there is a break in the circuit, all the electrons stop flowing.
Electrons can only flow in a complete circuit.
Questions
1
Name the particles that move around a circuit when current flows.
2
Copy the sentences and use words from the list to complete them.
Each word may be used once, more than once or not at all.
attracted repelled positive
−
−
−
−
−
−
−
Electrons are negatively charged so they move toward the
positive terminal in a circuit.
Opposite charges attract, and like charges repel. To attract means to pull
together and repel means to push apart. That means:
positive and negative attract
−
−
−
−
−
−
−
−
−
−
−
Electrons have a negative charge.
•
−
−
−
−
−
−
−
−
negative
electrons
atoms
Current in a circuit is the movement of ………………… .
These particles have a ………………… charge.
These particles are ………………… by the positive terminal of a
battery and ………………… by the negative terminal of a battery.
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+
9.1 Flow of electricity
Activity 9.1.1
Modelling electron flow
In this activity, you will use a model to show how current flows in a circuit.
Work in groups of four to six.
You will need:
•
a ball of string, scissors, coloured tape or coloured marker pen
1
Tie the ends of the string together to form a large loop. The loop must be long
enough to be held by all the people in the group. Attach coloured tape or make
coloured marks on the string at equally spaced intervals. The intervals should be
about 10 cm long.
2
In your group, stand in a circle facing toward the centre of the circle.
3
Each person should hold the loop of string in front of them in both hands, so the
string forms a circle. Hold the string so that it is quite tight but can move.
4
The people in the group are the components in the circuit. One person is the cell.
The person who is the cell must pull the string around through the hands of the
other group members. The other group members can be components such as
lamps or buzzers.
5
Watch how the string moves. Use the coloured marks to see the movement of
the string.
Questions
Discuss these questions in your group.
1
What part of the circuit made the string move?
2
When the string started to move, was the speed the same all the way around the
circuit or different?
3
Was it possible for the string to be moving in one part of the circuit and not moving
in another part?
4
Name the particles represented by the coloured marks.
5
In what ways does this model:
a
correctly represent what happens in a circuit
b
not correctly represent what happens in a circuit?
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9 Electricity
Think like a scientist
Making predictions about current
In this task, you will make and test predictions about the flow of current in a circuit.
Work as a whole class.
You will need:
•
a power supply or battery
•
wires longer than 2 metres, or many short wires that can be connected end to end
•
4 identical lamps that can operate in series from the power supply
1
Make a circuit with one lamp close to the negative terminal of the power supply.
2
Place the next lamp several metres away from the first lamp, and another lamp a
similar distance from this lamp.
3
Place the fourth lamp close to the positive terminal of the power supply.
Do not switch on the lamps yet.
Questions
Discuss these questions as a whole class.
1
What will happen when the power supply is switched on?
Will all the lamps come on at the same time?
If not, in what order will they light?
2
a
Is this prediction testable?
b
What name is given to a testable prediction?
Now switch on and see what happens.
3
Describe what you observed.
4
Try to explain what happened in terms of the flow of electrons.
Self-assessment
What did you learn about current in a circuit? List as many things as possible.
Is there anything you’re still unsure about current in a circuit?
Summary checklist
I can describe how electrons move in circuits.
I can understand how to work out the direction that electrons move.
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9.2 Electrical circuits
9.2 Electrical circuits
In this topic you will:
•
learn how to draw and compare circuit diagrams
•
learn the circuit symbols for cells, switches, lamps, buzzers
and ammeters.
Getting started
Key words
Work in pairs.
ammeter
circuit diagram
circuit symbols
Discuss with your partner the role of each of these components
in a circuit:
a
cell
b
switch
c
lamp
d
buzzer
e
ammeter.
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9 Electricity
Circuit diagrams
Circuits can be shown in a drawing or a circuit diagram.
Advantages of circuit
diagrams compared
with pictures
•
cell
Circuit diagrams are easier
to draw.
•
The components have
standard symbols.
•
switch
lamp
This is a drawing of a simple circuit.
Wires are drawn with straight
lines, which is easy to interpret.
Circuit symbols
Components in circuits can look very different.
The picture shows how different some lamps can look.
Standard circuit symbols are used in circuit diagrams so there
is no confusion. The same symbols are used in all countries.
The table shows the names, symbols and functions of
some components.
Name
Ammeter
Symbol
A
These are all different types of lamp but
they all have the same circuit symbol.
Function
measures current in the circuit
Cell
provides energy to make current flow
Lamp
gives out light
Switch (open)
stops the flow of current when opened
Switch (closed)
starts the flow of current when closed
Buzzer
makes a buzzing sound
Common circuit symbols
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9.2 Electrical circuits
In the circuit symbol for a cell, the positive is the longer of the two lines.
The negative is the shorter line.
−
+
Take care when drawing circuit diagrams. Make sure:
•
there are no gaps in the lines, especially at the corners and where
wires meet components
•
wires are not drawn through components.
Comparing circuit diagrams
Different circuits are used to do different jobs.
This circuit contains a cell, a switch and a buzzer. The circuit could be
used in a doorbell. If the switch is pushed outside a door, it makes the
buzzer sound and attracts attention inside.
This circuit contains a cell, a switch, a lamp and an ammeter.
The ammeter measures the electric current. This circuit could
be used to light a room and measure the current flowing
though the circuit. By measuring the current, you could tell
if the cell needs to be replaced – a smaller current means the
cell is low on stored energy. The lamp would also become less
bright, but you might not notice until too late and you find
yourself sitting in the dark!
A
Questions
1
Draw the circuit symbol for:
a
a lamp
b
a cell
c
a buzzer
d
a closed switch.
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9 Electricity
2
Arun draws a circuit diagram with a cell, a switch and a lamp.
He makes three mistakes.
Describe the three mistakes in the diagram.
3
Which of these circuits could be used to measure the current in a buzzer?
A
B
–
–
+
+
C
D
–
–
+
+
A
A
Think like a scientist
Drawing circuit diagrams
Work individually.
Draw circuit diagrams for each of these jobs.
A Two lamps that can be switched on and off together in a car.
B
A buzzer on a front door with a lamp that comes on at the same time as the buzzer.
C Three lamps that operate all the time, with a way to measure current in the lamps.
Questions
1
Now swap your circuit diagrams with someone else. Are they the same?
2
Can two circuit diagrams be different and both correct? Explain your answer.
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9.2 Electrical circuits
Continued
Self-assessment
Write a number from 1 to 5 for each of these statements.
The number represents how confident you are.
Use 1 for ‘not confident’.
Use 5 for ‘very confident’.
•
I can remember all the circuit symbols in the table.
•
I can draw circuit diagrams correctly and accurately.
•
I can tell what the circuits in different circuit diagrams could be used for.
Activity 9.2.1
Circuit uses
Work in groups of three or four.
Look at this circuit diagram.
Discuss what this circuit could be used for.
–
Make a list of all the possible uses.
+
Summary checklist
I can recognise the circuit symbols for a cell, a switch, a lamp,
a buzzer and an ammeter.
I can draw the circuit symbols for a cell, a switch, a lamp, a buzzer
and an ammeter.
I can draw a circuit diagram containing any of these components.
I can recognise and compare the jobs of different circuits from their
circuit diagrams.
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9 Electricity
9.3 Measuring the flow
of current
In this topic you will:
•
learn the unit for measuring current
•
learn how to measure current
•
learn a rule about current in series circuits.
Getting started
Key words
1
Name the particles that move in wires when current flows.
2
a
Name the component that is used in a circuit to measure
current.
amps
in series
b
Draw the circuit symbol for this component.
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9.3 Measuring the flow of current
Measuring current
In Topic 9.1 you saw that electrons move
when current flows.
When electrons move more quickly, the current
increases.
0
5
10 15
A
20
When electrons move more slowly, the current
decreases.
In Topic 9.2 you saw that you can use an
ammeter to measure current.
Current is measured in units called amps.
Amps have the symbol A.
There are different types of ammeter but they all do the
same job.
The picture shows two different ammeters.
Look carefully at the ammeters in the picture. They both have two
terminals, for wires to be attached. One terminal is red and the other
terminal is black.
In a circuit, the red terminal of the ammeter must be connected to
the positive terminal of the power supply. The red terminal may be
connected directly, or through other components, to the positive
terminal of the power supply.
Both ends of the ammeter are the same in a circuit diagram. You do
not need to show the red and black terminals on the circuit symbol
for an ammeter.
Ammeters are always
connected in series with
other components in a
circuit. If the components
are connected in series they
are all connected end-toend, one after another, and
there are no branches in
the circuit.
The drawing shows an
ammeter connected in series
with a battery, a switch and
a lamp. The circuit diagram
shows the same circuit.
this will be changed
back to version showing
Marcus in full, please
don't supply next proofs
until you have it. CUP to
supply.
cell
switch
+
Tech-Set: Awaiting new
artwork
–
1 : 27
lamp
ammeter
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9 Electricity
Questions
1
Name the unit used to measure current.
2
The diagram shows four different ammeters in four different circuits.
Write down the current shown on each ammeter. Include the unit in
your answer.
5
0
10
15
A
0
6 8
2 4
A
1500
1000
10
500
0
A
3
B
C
D
Copy the sentence and use words from the list to complete it.
Each word may be used once, more than once or not at all.
slower faster electrons atoms
The greater the current in a circuit, the ………………… the flow of
………………… .
4
Marcus has a circuit with a cell, a lamp and a buzzer.
He wants to measure the current in the circuit.
Which is the correct way to connect the ammeter in this circuit?
A
B
C
A
–
–
+
+
+
–
D
+
–
A
A
Activity 9.3.1
Drawing ammeter scales
In this activity, you will draw the scale for ammeters.
Work in pairs.
Draw an ammeter scale and mark the scale with numbers and divisions. The scale should
look like one of those in question 2.
Do not add the pointer to the scale.
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9.3 Measuring the flow of current
Continued
Write a current beside your ammeter scale. Make sure the current you write is within the
scale you have drawn.
Start with a whole number of amps, such as 4 A or 2.0 A.
Swap your drawing with your partner. Your partner will add the pointer to the drawing.
The pointer should be in the correct place to match your current.
Swap your drawings back again. Is the pointer in the correct place?
You can progress to decimal numbers, such as 1.7 A. Make sure your drawing has the
correct number of divisions between whole numbers.
Swap drawings again and check them as before.
Self-assessment
Which was more difficult:
•
drawing the scale correctly
•
putting the pointer in the correct place?
Think like a scientist
Making predictions about current
In this task, you will make and test predictions about current in a circuit.
Work in groups.
You will need (for each group):
a cell (or cells) that can operate two lamps in series, a switch, lamps,
an ammeter, wires and connectors
Part 1
1
Connect the circuit so that the lamps and the switch are in
series with the cell (or cells), as shown. Do not include the
ammeter yet.
2
Copy the circuit diagram.
3
Add arrows to your circuit diagram to show the direction
that electrons flow through the circuit.
+
–
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9 Electricity
Continued
Question
1
You are going to measure the current at different positions in the circuit. You will do
this by placing the ammeter in the positions X, Y and Z, as shown.
a
A
A
A
X
Y
Z
Predict what will happen to current going around the circuit.
Choose one statement.
A Current will stay the same all the way around the circuit.
B
Current will decrease as it goes around the circuit.
C Current will increase as it goes around the circuit.
b
Explain your prediction.
Part 2
4
Connect the ammeter into your circuit. Connect it at position X.
5
Close the switch and record the ammeter reading.
6
Do this two more times, once with the ammeter in position Y, and once with the
ammeter in position Z. Remember to open the switch before you make changes.
7
Copy the three circuit diagrams.
8
Write your ammeter readings next to each circuit diagram.
Questions
2
Describe the trend in your results.
3
Was your prediction from question 1 correct?
4
Explain your results. Use ideas about how electrons move in wires.
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9.3 Measuring the flow of current
Answer the questions that apply to you.
If your prediction was not correct:
•
Did the result surprise you?
•
How will you remember this result?
If your prediction was correct:
•
How did you work out what would happen?
•
How will you remember this result when you use other
series circuits?
Summary checklist
I can recall the unit of current and its symbol.
I can take accurate readings from an ammeter.
I can draw a circuit diagram with an ammeter connected correctly.
I can explain how to connect an ammeter in a circuit.
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9 Electricity
9.4 Conductors and insulators
In this topic you will:
•
discover the difference between electrical conductors
and insulators
•
learn about uses for conductors and insulators
•
test some materials for electrical conduction or insulation.
Getting started
Key words
Work in pairs.
allow current
to flow
conduct
electricity
conductor
inhibit
insulator
Complete the sentences. Use words from the list.
The words may be used once, more than once or not at all.
are free to move cannot move
electrons
atoms
wires
When current flows, particles called ………………… move.
In metals, these particles ………………… .
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9.4 Conductors and insulators
Conductors
Conductors are materials that
conduct electricity.
That means conductors allow current
to flow. Electric current can flow
through a conductor.
You saw in Topic 9.1 that electrons
move when current flows.
Therefore, a conductor is a material
in which electrons are free to move.
Conductors allow electrons to flow.
All metals are conductors.
Wires that carry electric current are
made from metal.
Metals conduct electricity because electrons in metals are free to move.
Most wires in houses and schools
are made from copper, with a plastic
coating.
Wires that cover long distances are usually
made from aluminium or steel. These metals are
cheaper than copper.
Copper wire
Some circuits, such as those in phones
and laptops, do not use wires. The printed
circuit board in the bottom right picture has
copper tracks instead of wires. The tracks are
green because the copper is coated with another
material.
Some wires are hundreds of km long.
Plastic coating
This printed circuit uses copper tracks instead of wires.
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9 Electricity
Insulators
Electrical insulators are materials that do not allow
current to flow through.
Most non-metals, such as plastic, wood, air and
cotton, are insulators.
In an insulator, the electrons are not free to move.
Because the electrons are not free to move, current
cannot flow. Insulators inhibit electron flow.
Insulators are used to keep people safe from
electricity.
The plug in the picture below is made from
plastic so people can touch the plug. The wire
coming from the plug is also coated in plastic
to protect people from electric shocks.
Plastic insulation on wires is also useful
because the plastic can be coloured differently
to identify each wire.
The insulators on these power lines stop the
current from flowing from the wires into the
metal pylon. If the current flowed to the pylon,
electrical energy would be dissipated into the
ground. Also, people and animals touching the
pylon would get electric shocks.
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metal pylon
insulators
conductors
9.4 Conductors and insulators
Questions
1
Copy the sentences and use words from the list to complete them.
plastic steel aluminium wood
Examples of electrical conductors include ………………… and
…………………
Examples of electrical insulators include ………………… and
…………………
2
Copper is used to make wires for home use. Copper is a good
conductor of electricity.
Silver is a better conductor of electricity than copper.
Suggest why wires for home use are not made from silver.
3
The drawing shows some types of plugs that are used in
different countries.
body
pins
Explain why:
4
a
the bodies of the plugs are made from plastic
b
the pins on the plugs are made from metal.
Explain, in terms of particles, the difference between conductors
and insulators.
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9 Electricity
Activity 9.4.1
Conduct or insulate?
Work in groups.
You will need:
• a piece of paper
• a pen • a pencil • a ruler
Use the ruler to make a large table on a sheet of paper, with these headings.
Object
Conductor or
insulator
Reason
Put the names of each of these objects into the table and complete the other columns.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Self-assessment
How many of the objects did you classify correctly as conductors or insulators?
Did you get the reasons correct?
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9.4 Conductors and insulators
Think like a scientist
Conductor or insulator?
In this task, you will test some materials to find out whether they are conductors or
insulators.
Work in pairs or groups of three.
You will need (for each group):
• a battery or cell
• a lamp
• crocodile clips
• wires
• a selection of materials to test, such as items found in the classroom
1
Set up a circuit as shown in the drawing.
Updated artwork now
showing Sofia supplied
in July.
Tech-Set: new artwork
has not been supplied
cell
lamp
clips
2
Touch the crocodile clips together and watch what happens to the lamp.
3
Test some materials by connecting the materials between the crocodile clips.
Questions
1
Explain why you touched the crocodile clips together before you started.
2
Explain how the test works.
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9 Electricity
Continued
3
Present your results in a suitable way.
4
Describe any trends or patterns in your results.
5
Some objects that are made from metal may appear to be insulators in this test.
a
Explain why.
b
Describe how you could show that these metals are actually conductors.
Summary checklist
I can describe what is meant by ‘electrical conductor’
and ‘insulator’.
I can understand how conduction and insulation work, in terms
of electrons.
I can recall some examples of conductors and insulators.
I can describe some uses of conductors and insulators.
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9.5 Adding or removing components
9.5 Adding or removing
components
In this topic you will:
•
find out what happens to current when you add more cells in
a circuit
•
find out what happens to current when you add more lamps
in a circuit.
Getting started
Key words
Work in pairs to answer these questions.
adding
components
dimmer
position
removing
components
1
2
a
Name the unit for measuring current.
a
Give the symbol for this unit.
Complete the sentences.
a
Current in a circuit is the flow of particles called
………………… .
b
As current increases, the flow of these particles gets
………………… .
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9 Electricity
Current in a series circuit
If you did Think like a scientist: Making
predictions about current in Topic 9.3, you may
remember that current is the same all the way
around a series circuit.
You can think of the electrons in a series circuit
like a train. All parts of the train move at the
same speed on the track. The back of the train
cannot go faster than the front of the train. As
soon as one part of the train moves, all of the
train will move.
–
A
+
–
A
+
The ammeter will give the same reading in both these
circuits if the components are identical.
Electrons flow at the same speed in the wires of a series circuit. When
electrons start to flow in one part of the circuit, they all start to flow.
That means you can put an ammeter at any position in a series circuit
and it will give the same result.
It also means that you can put the same components of a series circuit
in a different order and the current will be the same.
Adding components or removing components will affect the current.
The effect depends on what components are changed.
Adding or removing cells
You saw in Topic 3.5 that cells and batteries are
stores of chemical energy. In a complete circuit,
the chemical energy gets changed to electrical
energy.
That means if you add more cells to a circuit,
you have more chemical energy to change into
electrical energy in the circuit.
A
A
1.4 A
2.8 A
Look at the two circuits. Each component is identical in both circuits.
The circuit with two cells has double the electrical energy of the circuit
with one cell.
The lamp will be brighter.
The ammeter in the circuit with two cells shows that the current
is doubled.
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9.5 Adding or removing components
You need to be careful adding more cells to a circuit. The lamps can be
damaged and the wires can get hot.
Adding more cells increases the current when the other components are
kept the same.
Removing cells decreases the current when the other components are
kept the same.
Adding or removing lamps
You saw in Topic 3.5 that lamps change electrical energy to light energy
and thermal energy.
Electrons carry electrical energy around a circuit. When the electrons
pass through a lamp, the electrons transfer some of their electrical
energy to the lamp. The lamp changes the electrical energy into light
energy and thermal energy.
Remember that the current is the same at all positions in a series circuit.
Putting a lamp in a circuit will make the electrons move more slowly, but
they move more slowly the whole way around the circuit.
The circuit with two lamps transfers twice as
much energy as the circuit with one lamp. The
lamps will be dimmer. That means they do not
shine as brightly.
This makes the electrons move at half the speed,
so the reading on the ammeter is halved.
A
A
1.4 A
0.7 A
Adding more lamps decreases the current when
the other components are kept the same.
Removing lamps increases the current when the other components are
kept the same.
Questions
1
Which statement is true about current in any series circuit?
Write the letter.
A Current decreases around the circuit.
B
Current increases around the circuit.
C Current stays the same around the circuit.
D Current increases and decreases around the circuit.
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9 Electricity
2
Look at these two circuit diagrams. Each component is identical in
both circuits.
A
B
A
3
A
a
Which of these circuits has a larger current? Write the letter.
b
Explain your answer.
Look at these two circuit diagrams. Each component is identical in
both circuits.
C
D
A
4
A
a
Which of these circuits has a larger current? Write the letter.
b
Explain your answer.
Look at the circuit diagram.
A
a
Describe two ways to increase the current in this circuit.
b
Describe two ways to decrease the current in this circuit.
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9.5 Adding or removing components
Activity 9.5.1
Model circuits
In this activity, you will make models of circuits from cards.
Work in groups.
You will need:
• paper or card • scissors • a pen or pencil
Start by cutting out 10 equal-sized squares of paper or card. The squares should be about
4–5 cm wide.
Draw circuit symbols on each card with wires that go to the end of the card. The cards will
need to fit together to make circuits.
You should have:
•
three cards with a cell
•
three cards with a lamp
•
four cards with circuit corners.
The cards should look something like this.
Work on a large sheet of paper, where you can draw extra lengths of wire if needed.
Questions
1
Build a series circuit with three cells and three lamps.
2
a
Make one change that would increase the current in your circuit.
b
Discuss in your group why this change would increase the current.
Put the circuit back together with three cells and three lamps.
3
a
Make one change that would decrease the current in your circuit.
b
4
Discuss in your group why this change would decrease the current.
Make another, different series circuit.
Discuss whether the current will be different from the first circuit and why.
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9 Electricity
Continued
Peer assessment
•
Did everyone in the group agree with the changes?
•
Did everyone in the group agree with the explanations?
Think like a scientist
Measuring current
In this task, you will measure current in circuits when components are added and
removed.
Work in groups.
You will need (for each group):
• 3 cells • 3 lamps • an ammeter • wires • a switch
Safety
You must avoid damage to components where possible.
Follow these rules.
•
Do not remove all the lamps from a circuit, leaving only the cells.
•
Do not connect an ammeter directly to cells without lamps.
•
If a lamp appears too bright, switch off immediately.
Part 1
1
Build this circuit.
2
Close the switch and record the current.
3
Add another lamp.
4
Record the current with
two lamps.
5
Repeat with three lamps.
A
Questions
1
Discuss in your group the best way to display these results.
2
Display the results in the way your group decided.
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9.5 Adding or removing components
Continued
Part 2
6
Build this circuit.
7
Close the switch and record the current.
8
Repeat with two and then three cells.
9
Display your results in an appropriate way.
A
Questions
3
a
Make conclusions about your results.
b
Suggest any limitations of the conclusions.
•
How do you build a circuit from a circuit diagram?
•
Is it easy or difficult to build circuits from circuit diagrams?
Rate your answer from 1 (very easy) to 5 (very difficult).
•
If you find building a circuit from a circuit diagram difficult,
what could make it easier?
Summary checklist
I can understand that the current is the same all around a series circuit.
I can predict what will happen to current in the same series circuit when more cells are added.
I can predict what will happen to current in the same series circuit when more lamps are
added.
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9 Electricity
Project: Paying for electricity
Many homes and schools are connected to electricity supplies.
People who use the electricity pay for how much they use.
Task 1
Work individually for this task.
Find out how much current some
electrical items use. Do not include
items that work only on batteries.
For example, most phone chargers
use about 1.5 A.
When searching for this information,
you may find a number with the
unit W. This is not the current. You
can find the current by dividing this
number by the voltage. In most countries, the voltage is about 230 V. In some countries,
the voltage is 110 V or 120 V. For example, if you find something with 500 W, and your
500
voltage is 230 V, the current used is
= 2.2 A.
230
Display your results in a bar chart.
Questions
1
Which electrical item in your list uses the most current?
2
Which electrical item in your list uses the least current?
3
Explain why a bar chart is better than a line graph for showing these results.
Task 2
Work in groups for this task.
Around the year 1870, some cities had the first electricity supplies.
People in 1870 also had to pay for electricity. The amount they had to pay depended on
the number of electric lamps they had.
Someone who had four lamps would pay double what someone who had two lamps paid.
This method of payment was called the pay-per-lamp method.
In 1870, there was no technology to measure the quantity of electricity that was actually
used.
Today, the amount people pay depends on the current they use and the time the current
is flowing.
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9.5 Adding or removing components
Continued
Questions
In your groups, discuss answers to these questions.
1
Suggest reasons why the pay-per-lamp method was
fair for 1870.
2
Suggest reasons why the pay-per-lamp method was
not fair for 1870.
3
Would a pay-per-lamp method be fair today?
Explain your answer.
An electric lamp from 1870
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9 Electricity
Check your Progress
9.1 a
Name the particles that flow inside a wire when current flows.
[1]
b
State the charge on these particles.
[1]
c
Explain, with reference to the cell, what direction these particles flow in a circuit. [2]
9.2 a
b
Draw the circuit symbols for:
i
a cell
[1]
ii
an open switch
[1]
iii
a lamp
[1]
iv
an ammeter
[1]
v
a buzzer.
[1]
[3]
Draw a series circuit with a cell, a lamp and a switch.
9.3 Which of these ammeters will give a correct result for the current in the lamp?
[1]
Write the letter.
A
10 15
5
0
A
B
20
−
10 15
5
0
A
20
+
C
+
D
+
0
5
10 15
A
−
20
−
0
5
+
10 15
A
9.4 Which of these can be measured in amps?
Write all the correct letters.
A brightness of a lamp
B
−
loudness of a buzzer
C current in a circuit
D speed of electron flow
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20
[1]
9 Electricity
9.5 Arun has a circuit for testing whether an object is a conductor or an insulator.
cell
lamp
crocodile clips
a
Explain why the lamp will light if Arun connects a conductor into the circuit. [2]
b
Arun puts a different object into the circuit.
[2]
The lamp does not light.
Suggest two possible reasons for this result.
c
Copy the sentences and use the words from the list to complete them.
[1]
inhibits free to move allows not free to move
A conductor … electron flow.
In a conductor, electrons are … .
An insulator … electron flow.
In an insulator, electrons are … .
9.6 Look at the circuit diagram.
Draw another circuit that would have:
a
a larger current flowing than the one in this diagram
[2]
b
a smaller current flowing than the one in this diagram.
[2]
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Glossary and Index
1.1
cell
cell membrane
cellulose
cell wall
chlorophyll
chloroplast
cytoplasm
magnify
mitochondrion
nucleus
SEE QUERY
LOG
In the text,
this word is
used as a
verb, but here
it is defined
as a noun.
sap vacuole
1.2
stain
Tech-Set:
For stain, no
comment in
the query
log
1.3
axon
capillary
the smallest unit from which all living things are made;
cells always have a cell membrane and cytoplasm,
and usually a nucleus
a very thin layer surrounding every cell, which controls
what enters and leaves the cell; in a plant cell, the cell
membrane is pressed tightly against the cell wall and
so cannot be seen as a separate structure
the material that the cell wall is made from
the outer layer of a plant cell, made from cellulose;
it gives support to the cell, but does not control what
enters or leaves it (note that fungi and bacteria also have
cell walls, but these are not made of cellulose)
a green pigment that absorbs energy from light; this
energy drives the reactions of photosynthesis
a structure found in some plant cells which looks green
because it contains chlorophyll; chloroplasts are the site of
photosynthesis
the material that fills a cell; it is a gel made of many
substances, including proteins, dissolved in water
to make something look bigger
a structure inside the cell where energy is released from food
a structure found in most cells, surrounded by a membrane,
in which chromosomes are found; information held on the
chromosomes controls the activities of the cell
a structure that is often, but not always, present in
plant cells; it contains a liquid called cell sap
a coloured substance or dye that is used to colour cells;
often, the stain will colour different parts of the cell
different colours, making it easier to pick out these parts
when viewing the cells through a microscope
a long extension in a neurone
the smallest type of blood vessel; capillaries supply
blood to all tissues in the body
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2
2
2
2
2
2
2
2
2
2
2
7
11
11
ciliated cell
cilia
dendrite
function
haemoglobin
mucus
neurone
palisade cell
pigment
red blood cell
root hair cell
specialised
1.4
ciliated epithelium
lower epidermis
onion epidermis
organism
organ
organ system
a cell found in the lining of the trachea and oviduct;
the cilia move in unison, like oars, which causes fluid
to move along the tube
tiny, hair-like structures that extend from the surface
of some cells
a short extension in a neurone
the job that something does or the role that it has
a protein that combines reversibly with oxygen; it takes
up oxygen when this is in a high concentration, e.g. at the
lungs, and releases oxygen when this is in a low
concentration, e.g. in a respiring tissue
a sticky substance that helps to trap dust particles and
bacteria in the respiratory passages or to lubricate surfaces,
e.g. in the lining of the digestive system
sometimes known as a nerve cell; a cell that is specialised
to transmit electrical impulses (action potentials) from
one part of the body to another
a cell found just beneath the upper surface of a leaf,
specialised to carry out photosynthesis
a coloured substance, such as haemoglobin
the most common type of cell in blood; human red
blood cells are circular with a depression in each side
(biconcave); they contain no nucleus to make more
space for haemoglobin
one of hundreds of cells found on the outer surface
of roots, close to the tip, which increase the surface area
of the root and, therefore, speed up the absorption of water
and mineral ions
(of a cell) with a structure that increases its ability to
carry out its function
a tissue made of animal cells with cilia that wave in unison
the layer of cells on the lower surface of a leaf
the thin sheet of cells that covers the inner surfaces
of the layers in an onion
a complete living thing
several different tissues working together to perform
a function, e.g. the stomach
several different organs working together to perform
a function, e.g. the digestive system
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palisade layer
spongy layer
tissue
upper epidermis
2.1
compressed
decision
flow
hypothesis
matter
particle
pour
properties
states of matter
theory
vacuum
vibrate
volume
2.2
boil
boiling point
changes of state
condensation
evaporation
freezes
measuring cylinder
melting point
melts
meniscus
the layer of tall photosynthetic cells just below the
upper epidermis of a leaf
the layer of photosynthetic cells just below the palisade
layer; there are large air spaces between the cells
a group of similar cells working together to perform
a function, e.g. ciliated epithelium
the layer of cells on the top surface of a leaf
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squeezed into a smaller space
conclusion
(of a liquid or gas) to move it smoothly, to pour
a suggestion for an explanation
the term for any type of material; everything that has
mass and takes up space is matter
a very small piece of matter that everything is made up of
(of a liquid or gas) to move it smoothly, to flow
the features of a material and how it behaves
all matter is either solid, liquid or gas
an idea to explain evidence
an area where there is nothing, that is, no particles at all
to move backwards and forwards repeatedly
the amount of space taken up by a solid, liquid or gas
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heating strongly and changing a liquid to a gas
the temperature at which a liquid changes to a gas
when matter changes from one state to another
changing from a gas to a liquid, for example water
vapour changing to liquid water
changing from a liquid to a gas, at a temperature below
boiling point
changing from a liquid to a solid
a piece of glassware designed for measuring the
volume of liquids
the temperature at which a solid changes to a liquid
changing from a solid to a liquid
the slight curve at the surface of a liquid, more
clearly seen when the liquid is in a narrow container
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steam
thermometer
water vapour
2.3
attractive forces
expand
heat energy
transferred
2.4
groundwater
open water
precipitation
surface run-off
transpiration
water cycle
2.5
atoms
element
groups
metals
nanotubes
non-metals
Periodic Table
periods
symbol
2.6
bonding
compound
water vapour produced when water boils and changes
from a liquid to a gas
equipment to measure temperature
water in the form of a gas
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these hold the particles together in solids and liquids
to get larger
heat, a form of energy, can move between the particles
and the environment
moved to or from one item to another
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rain water that has soaked into the soil
an expanse of an ocean, sea or large lake which is
distant from land and has no nearby islands or other
obstructions
a fall of rain, snow or hail
rain water that runs off the surface to rivers and streams
the process by which plants lose water to the atmosphere
the processes by which water is moved around the
environment from rivers to clouds and back again
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tiny particles of matter
a substance that is made of only one type of atom
vertical columns in the Periodic Table
types of element found on the left side of the
Periodic Table
nano means very small; so, a nanotube is a very small tube
types of element found on the right side of the
Periodic Table
arrangement of elements in order of the mass of their atoms
horizontal rows in the Periodic Table
used as a shorthand way of referring to an element
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the way in which atoms join together
a substance in which atoms of two or more elements are
bonded together
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formula
sodium chloride
2.7
composition
evaporating basin
filings
mixture
natural emissions
pipe-clay triangle
pure
uses chemical symbols to show how many atoms of
different elements are present in particle of an element
or compound
a compound of sodium and chlorine
what something is made up of
a piece of laboratory apparatus used to heat and evaporate
off water
small pieces of pure iron
substances that are mixed together but not chemically bonded
gases given off during natural processes, such as respiration
or photosynthesis (the process by which green plants
make food)
a piece of laboratory apparatus used to balance an
evaporating basin on a tripod
made of only one thing
3.1
accurate
being close to a true value
acts towards the centre gravity causes a force which pulls objects towards
the centre of a planet or star
contact force
the force from a surface on an object that is equal
and opposite to the weight of the object
Earth
the planet we live on
force of gravity
a force of attraction which is an example of a non-contact force
formula triangle
a method of using an equation
gravity
found around any object with mass; causes weight
and a force of attraction on other masses
kilograms
the unit of measure for mass
mass
the quantity of matter in an object, measured in kg
newtons
the unit of measure for force and weight
quantity
the amount of something; quantity is preferred in
science to ‘amount’
weight
the force of gravity on an object, measured in newtons (N)
3.2
axis
contradict
evidence
an imaginary line through the middle of a planet,
about which the planet spins
to go against or disagree with something
facts that support or contradict an hypothesis
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formed
hypothesis
model
nebula
observe
orbit
plane
spin
support
3.3
air resistance
circular
speed
vacuum
3.4
coastal
depth
earthquake
Earth tide
force of attraction
harbour
tidal force
tidal range
tide
volcano
created
a testable prediction
a way to represent something that cannot be seen directly
a cloud of dust and gas in space
to watch something happening
the path of a planet around the Sun or a satellite
(natural or artificial) around a planet
points are on the same plane if they could be placed
on the same flat surface
the circular movement of a planet around its own
axis, such as causes day and night on Earth
to agree with something
a force that acts against motion caused by objects
having to displace the air in front of them in order to move
the same shape as the circumference of a circle (orbits
of planets are actually elliptical, but are assumed to
be circular in this context)
distance moved per unit time (the word velocity should
not be used interchangeably with speed)
a region with no particles such as the space between
planets in the Solar System
describes places on land that are beside the sea or the ocean
the distance from the bottom of the ocean to the
surface of the ocean; how deep the ocean is
sudden movement in the Earth’s crust
the rise and fall of the land surface as a result of tidal forces
any type of force that causes objects to come together
a place (natural or artificial) where boats can load
or unload with protection from large waves
the force from the gravitational pull of the Moon and
the Sun that causes tides on Earth
difference in depth of water between high and low tides
twice daily rise and fall in ocean depth caused by gravity
from the Moon and the Sun
mountain where lava and gas can escape from beneath
the Earth’s crust
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3.5
chemical
form of energy stored in food a fuels
elastic
form of energy stored when objects change shape
electrical
energy carried in a circuit or stored in charged objects
energy
quantity that must be changed in order to do something
fuel
a store of chemical energy
gravitational potential form of energy stored when objects move higher
joule
the unit of energy
kinetic
energy associated with movement
light
energy that we can see
luminous
an object that gives out light
sound
energy transferred through vibrations
stored
energy contained in one place
thermal
the scientific term for heat energy
transferred
energy is transferred when it moves from one place to another
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3.6
changes in energy
change
event
process
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dissipated
recovered
useful
wasted energy
4.1
excretion
growth
movement
nutrition
reproduction
when energy changes from one state to another
when energy is converted from one store to another
something which happens that involves a change in energy
one or more events that result in energy changes
spread out into the surroundings in a way that cannot
be recovered
collected and used again
energy is described as useful when it is changed in
the way that we want
this is energy that is changed in a way that we do not want;
usually cannot be recovered
removing toxins or materials excess to requirements
from the body
a permanent increase in size
changing the position of all, or part, of the body
feeding: taking in nutrients to provide energy and materials
for growth
making more organisms of the same species
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respiration
sensitivity
4.2
electron microscope
influenza
protein
RNA
virus
4.3
fertile
identical
infertile
offspring
species
specimen
variation
4.4
dichotomous
key
5.1
brittle
conduct
ductile
breaking down food to release energy that the organism can use 121
detecting changes in the environment
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a microscope that uses electron beams instead of light
beams; it is able to achieve much higher resolution than
a light microscope
an illness caused by a virus, often known as flu; it affects
the respiratory system and usually results in a high temperature
polymers of amino acids; they are important nutrients
for living organisms, as they are used in growth and repair
a nucleic acid found in all living cells; most cells contain
both RNA and DNA, but some viruses contain only RNA
a particle made of either RNA or DNA, surrounded
by a protein coat; viruses hijack the machinery of a host
cell to replicate
able to have offspring
exactly the same
unable to reproduce, usually because gametes cannot be formed
children
defined here as a group of organisms that can reproduce
together to produce fertile offspring
a sample, for example a piece of rock, or a single organism
of a species
differences between members of the same species
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branching into two; most keys involve a statement to
which the user answers yes or no, or pairs of contrasting
statements to choose between
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an identification tool for objects or organisms; most keys
provide sets of statements for you to choose between, where the
answer leads to you another set of statements and finally an
identification
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breaks with a snap
can transfer heat or electrical energy
can be drawn out into strands or wires
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insulators
magnetic
malleable
materials
shatter
shiny
sonorous
cannot transfer heat or electrical energy
is attracted to a magnet
can easily be hammered into shape
the substances from which objects are made
breaks into many pieces
something that reflects light
rings like a bell
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distinguish
examine
touch
apparatus used in electrical circuits to join a wire
to a material
tell the difference between
to investigate or look at in detail
5.3
alloys
bronze
disrupts
steel
mixtures of metals
an alloy of copper and tin
upsets the pattern
an alloy of iron
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apparatus used to separate mixtures of liquids
glass container shaped like a cone
a paper placed in a filter funnel and used to separate
a solid from a liquid
apparatus used for separating a solid from a liquid
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contact
crocodile clips
5.4
condenser
conical flask
filter paper
filter tunnel
5.5
acid
alkali
corrosive
flammable
harmful
irritate
a substance which contains hydrogen particles and
has a pH lower than 7; the chemical opposite of
an alkali
a substance that contains hydroxide particles; the
chemical opposite of an acid
able to dissolve or eat away other materials such as
your skin
a substance that catches fire easily
causes damage
to cause itching or sores to your body
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oxidising
toxic
5.6
indicator
litmus
neutral
pH scale
universal indicator
a substance that gives off a large amount of heat
energy when in contact with other substances
able to poison you
a substance that changes to a different colour in acid
and alkali
a type of indicator
a substance that is neither acid nor alkali, is at pH7
measures how acidic or alkaline a substance is
a mixture of indicators that gives a range of colours
in solutions of different pH
6.1
backwards and forwards repeated movement in straight lines and in opposite
directions
loudness
a measure of how easy a sound of a certain pitch is
to hear; loud sounds are easier to hear than quieter sounds
medium
the substance that a wave passes through
particles
smallest parts of a substance
pitch
the highness or lowness of the tone of a sound, for
example musical notes of high pitch are higher in
the musical scale than those of low pitch
sound wave
vibrations of particles parallel to the direction of
transfer of sound energy
speed of sound
a measure of how fast a sound wave travels, which depends
on the medium
6.2
echo
effect on the sound
property
reflected
unwanted
6.3
continental drift
core
a reflected sound wave
how the features of a sound are changed
a characteristic feature of something
a wave is reflected when the wave meets a surface
then comes back from that surface
something which is undesirable or a nuisance
the theory that the Earth’s continents have slowly
changed position
the innermost part of the Earth, divided into a liquid
outer core and a solid inner core
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crust
magma
mantle
molten
tectonic plates
6.4
active
earthquake
extinct
fold mountains
inactive
lava
magnitude
plate boundaries
subduction
volcanoes
6.5
eclipse
lunar
opaque
partial
rays
the outer layer of the Earth that is made from solid rock
hot molten or semi-solid material in and below the
Earth’s crust
the layer within the Earth between the core and the
crust that is mostly solid
the word used to describe something which has melted
pieces of the Earth’s crust and upper mantle that
are about 100 km thick
a volcano is active if it has erupted in the last few
thousand years and is likely to erupt again
sudden movement in the Earth’s crust and upper
mantle caused by the build-up of pressure between
two tectonic plates
a volcano becomes extinct when it is very unlikely
to erupt again because the volcano has no more supply
of magma
where the Earth’s crust is pushed upward because of
two tectonic plates pushing against each other
a volcano is inactive if it could possibly erupt in the future
but has not erupted for thousands of years
molten rock coming out onto the Earth’s surface
the size of something; for earthquakes this is a number
which allows comparisons to be made between the strength
of earthquakes
the place where two or more tectonic plates are side
by side
one tectonic plate moving under another tectonic plate
at a plate boundary
openings in the Earth’s crust where lava, ash and gas
can come out onto the Earth’s surface
shadow caused by the Moon or caused by the Earth
description of something to do with the Moon
description of an object that does not allow light to
pass through; the opposite of transparent
description of a solar eclipse where the Moon only partly
blocks the light from the Sun
the straight lines that show the direction of light
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shadow
solar
total
7.1
agar jelly
area where light has been blocked by an opaque object
description of something to do with the Sun
description of a solar eclipse where the Moon completely
blocks the light from the Sun
yeast
a gel made by mixing agar powder with water and
heating to dissolve; the liquid mixture can be poured into
a Petri dish and allowed to set; nutrients can be added
to encourage growth of microorganisms
organisms made of a single cell, or several similar cells,
that have a structure similar to plant cells
single-celled microorganisms whose cells are smaller
than those of plants and animals; they have cell walls
but no nucleus
in this context, a group of cells that have been produced
by the repeated division of a single cell of a bacterium
or fungus
organisms with cells that have cell walls and a nucleus,
but differ from plants in that the cell walls are not made
of cellulose, and they never contain chlorophyll and
do not photosynthesise; some fungi are microorganisms
any organism that is too small to be seen without a microscope;
many microorganisms are made of a single cell
a reproductive body produced by a fungus at certain
times of its life cycle; the word ‘mushroom’ tends to
be used when the structure is edible
a shallow, circular dish with a lid, made of clear plastic
or glass
organisms made of a single cell that has a structure
similar to animal cells
made of only one cell
complete absence of living organisms; equipment for
growing microorganisms must be sterilised before and
after use
a term that generally means the same as mushroom,
but that tends to be used when the structure is not edible
a single-celled fungus
7.2
carnivore
an animal that eats only other animals
algae
bacteria
colony
fungi
microorgansism
mushroom
Petri dish
protozoa
single-celled
sterile
toadstool
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consumer
ecology
energy transfer
food chain
food web
herbivore
predator
prey
producer
7.3
decay
decomposer
mould
organic matter
rot
7.4
dung
nutrients
an organism that obtains its energy by feeding on
other organisms
the study of organisms in their environment
the process in which energy is moved from one place
to another; in a food chain, arrows show how energy
is transferred from one organism to the next
a flow diagram showing how energy moves from one
organism to another through feeding
a flow diagram showing how different food chains interact
an organism that eats only plants
an animal that kills and eats other animals
an animal that is killed and eaten by other animals
an organism that uses inorganic substances to make
organic ones; the organic substances contain energy
that can be passed on to other organisms; in most
food webs, producers do this through photosynthesis,
in which the source of energy is sunlight
to cause something to break down and lose
its form; decay of plant and animal remains releases
nutrients from them into the environment
an organism that causes decay; the term is generally used
to refer to organisms that feed by releasing enzymes outside
their bodies and then absorbing the soluble nutrients that are
produced by the breakdown of substances in the medium
in which they are growing
any type of visible fungus, generally used to refer to
a covering of fungus on food or other organic material
such as leather or paper
substances derived from living organisms
another word for decay
animal faeces; generally used for the faeces of
larger animals
substances that are used by organisms to provide useable
energy, or materials for building new cells
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chemical reaction
a process in which one or more substances are changed to
one or more different substances. In the reaction, the atoms
of the starting substances are rearranged, forming new
substances that have different properties
join together
substance that you start with in a chemical reaction
new substance made in a chemical reaction
interact and change
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decay
digest
filtrate
indigestion
neutralisation
neutralised
piece of laboratory glassware used for adding measured
volumes of liquid
to rot; e.g. acid in the mouth can cause the teeth to decay
to break down food into small pieces that can be absorbed
the liquid that comes through a filter paper
pain or discomfort in the digestive system
changing an acid or an alkali into a solution at pH 7
an acid or alkali that has been changed into a solution at pH 7
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remedy
variable
a treatment or medicine that relieves a disease or condition
something that can change in an investigation
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combine
reactant
product
react
8.2
burette
8.4
cloudy
glowing
precipitate
9.1
attract
battery
cell
components
current
as in a solution becoming cloudy; it starts to form a
white deposit
not fully alight, as when a lighted splint is shaken so that
the flame goes out
an insoluble substance that forms from a reaction
in a solution
cause things to move closer together by a force; opposite
of repel
two or more cells connected together in series
the component drives the flow of current by changing
chemical energy to electrical energy; most cells are 1.5 V
parts of a circuit such as cells, lamps and switches; wires are
not considered to be components
the flow of electrons in a circuit
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electrons
free to move
negative charge
repel
terminals
9.2
ammeter
circuit diagram
circuit symbols
9.3
amps
in series
9.4
allow current to flow
conduct electricity
conductor
inhibit
insulator
9.5
adding components
dimmer
position
removing components
negatively charged particles which flow in wires to create current
electrons in conductors such as wires, are not fixed or
attached in one position, so can move when a cell is
connected into a complete circuit
the property of electrons which makes them attracted
to positive charges and repelled by other negative charges
cause things to move apart by a force; opposite of attract
the connectors on a component; some of these are
labelled + and –, such as on a cell, a battery or an ammeter;
others, such as on a switch or a lamp, are not labelled
a device for measuring current; ammeters can be
digital or analogue and their output shows the current
in amps (A) or milliamps (mA)
a way to represent a circuit using straight lines for wires
and international standard symbol for components
a set of international standard diagrams to represent
electrical components
the unit of current; amps is a shortened and more
commonly used form of the word amperes
components are in series with each other when connected
end-to-end so that the current has a single path to follow
through the components
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having electrons that are free to move
to allow current to flow
a material where electrons are free to move so that current
can flow
to stop something from happening
a material where the electrons are not free to move, so that
current cannot flow
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putting more cells or more lamps, and so on, into a circuit
less bright (of a lamp)
a specific point in a circuit
taking cells or lamps out of a circuit
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