CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 1.1A
Plant cell structure and function
Cell wall – a strong layer of cellulose that helps to hold the cell in shape.
Cell membrane – a thin layer around the outside of the cell that controls what goes into and out of
the cell.
Cytoplasm – a clear jelly where chemical reactions happen.
Chloroplast – where the plant makes its food.
Nucleus – controls the activities of the cell.
Mitochondrion – where energy is released from food.
Sap vacuole – a space containing a solution of sugars in water.
Worksheet 1.1B
Plant cell structure and function
Chloroplast – where the plant makes its food.
Nucleus – controls the activities of the cell.
Cytoplasm – a clear jelly where chemical reactions happen.
Sap vacuole – a space containing a solution of sugars in water.
Mitochondrion – where energy is released from food.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
1
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Cell membrane – a thin layer around the outside of the cell that controls what goes into and out
of the cell.
Cell wall – a strong layer of cellulose that helps to hold the cell in shape.
Worksheet 1.1C
Plant cell structure and function
1
There is a wide variety of possible answers that learners might give. Look for these attributes in each
answer:
• The sentence correctly describes the function of each part, as given in the Learner’s Book. Note
that some learners may have read beyond the descriptions in the Learner’s Book and provide extra
detail or further information. If so, you may need to check that they are correct.
• The sentences use the learner’s own words and are not copied from the Learner’s Book.
• The instructions have been followed carefully, so that only one sentence has been written for each
structure.
• The sentence is written in a clear manner.
Worksheet 1.2A
Comparing plant and animal cells
Animal cells
Plant cells
have a cell membrane
have a cell membrane
do not have a cell wall
have a cell wall
have a nucleus
have a nucleus
never have chloroplasts
sometimes have chloroplasts
have mitochondria
have mitochondria
have cytoplasm
have cytoplasm
do not have a sap vacuole
have a sap vacuole
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
2
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 1.2B
Comparing plant and animal cells
Structure
Is it found in plant cells?
Is it found in animal cells?
cell walls
yes
no
nucleus
yes
yes
cytoplasm
yes
yes
cell membrane
yes
yes
sap vacuole
yes
no
mitochondria
yes
yes
chloroplasts
sometimes
no
Worksheet 1.2C
Comparing plant and animal cells
1–4 There are no ‘correct’ answers for this open-ended task.
Most learners are likely to use a table or chart of some kind to display their response, but be prepared
to accept more imaginative ideas.
Look for:
• a well-designed table, with columns clearly headed and clear entries that are easy to understand
• similarities and differences both shown clearly
• all similarities and differences included – see answers for 1.2B above for reference.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
3
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 1.3
Specialised cells
Standard and help sheet
Heading: Root hair cell
Sentence: This cell absorbs water from the soil.
Heading: Red blood cell
Sentence: This cell transports oxygen.
Heading: Ciliated cell
Sentence: This cell sweeps mucus upwards.
Heading: Neurone
Sentence: This cell transmits electrical signals.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
4
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Heading: Palisade cell
Sentence: This cell makes food by photosynthesis.
Extension sheet
Learners add some of the following labels:
on the root hair cell:
• long extension to allow water to move easily from the soil into the cell
• (learners could make reference to increasing the surface area of the cell)
on the red blood cell:
• no nucleus, to make extra space for haemoglobin
• haemoglobin in cytoplasm, to carry oxygen
on the ciliated cell:
• cilia can move and sweep mucus up and away from the lungs
on the neurone:
• axon is a long strand of cytoplasm that transmits electrical signals over long distances very quickly
• dendrites collect signals from other neurones
on the palisade cell:
• many chloroplasts containing chlorophyll, to absorb energy from sunlight and use it to make food
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
5
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 1.4A
Human organs and systems
3 Outline containing the respiratory and digestive systems, coloured green and yellow, respectively.
4 Outline containing the nervous and circulatory systems, coloured blue and red respectively.
Worksheet 1.4B
Human organs and systems
1 and 2 Outline showing the stomach, brain, mouth, heart, small intestine, lungs, trachea and spinal chord,
all clearly labelled.
The circulatory, respiratory, digestive and nervous systems should also be shown, coloured in red,
green, yellow and blue, respectively.
Worksheet 1.4C
Human organs and systems
Learners can give a wide variety of answers to each of the tasks on this Worksheet. Look for the
following:
1 Learners’ own choice of two organs.
2a and 3a
The drawing should:
•
•
•
•
have a heading with the name of the organ
be simple and clear, using unbroken lines and little or no shading
have at least two labels
have ruled lines clearly linking the label to the part.
2b and 3b
The answer should give a simple description of the function of the chosen organ.
2c and 3c
The answer should mention at least two different tissues that are found in the organ and
provide a simple description of each. If a learner has chosen the stomach, they could
mention muscle tissue, connective tissue, nerve tissue and so on.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
6
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 2.2A
Finding mistakes
1
Sofia has written the temperature of the water at the start of her experiment as 0°C. She has taken it
from the same tap as everyone else, so it cannot be at 0°C.
2
Arun has not written the units for temperature in his results table and the second mistake is that the
temperature of the water at two minutes is exactly the same as the temperature at one minute.
3
Marcus’s result at two minutes is only 5°C above the temperature at one minute. All the other
temperature increases are at least 10°C per minute.
Worksheet 2.2B
Identifying anomalous results
1
Zara’s readings at three minutes and nine minutes do not seem to fit the pattern. The result at three
minutes is the same as at two minutes. This is unlikely, unless she stopped heating the water. The
temperature at nine minutes is lower than at eight minutes and is the same as at seven minutes. This is
very unlikely.
2
Zara should not use these readings in plotting the graph. She should repeat this investigation.
3
Arun has made a mistake in recording his results, because the table shows he started his investigation
at one minute instead of at 0 minutes. He has taken the temperature of the water before heating it and
recorded it in the table as if he had heated the water for one minute (or possibly he has failed to take
the temperature at the start before heating, but this is unlikely because he started with water from the
same source as Zara, at 20°C).
Worksheet 2.2C
Finding errors in graphs
1
Sofia has put the axes the wrong way round: time should be along the x-axis and temperature on the
y-axis. On the temperature scale the reading for 52°C has been left out.
2
On Marcus’s graph the points at 0 minutes, four minutes and six minutes have been plotted
incorrectly. These should be circled.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
7
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 2.3A
Linking words and meanings
When a liquid changes to a gas = evaporation
When a solid changes to a liquid = melting
When a gas changes to a liquid = condensation
When a liquid changes to a solid = freezing
Worksheet 2.3B
Making links
1
For answers to this question, accept any relevant link between the two items. For example:
a
A liquid can change state and become a gas if it is heated.
b When a solid is heated until it melts, it changes state and becomes a liquid.
c
When a liquid is heated until it evaporates, it changes state to become a gas.
d When a solid is heated the particles vibrate more and more.
2
e
The particles in a solid are arranged in fixed positions in regular rows, so they cannot
change places.
a
To change from a gas to a liquid.
b When a solid changes to a liquid or a liquid to a gas or a solid or vice versa.
c
The properties of a substance are its qualities and the ways in which it behaves.
d A vacuum is a place that contains no particles.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
8
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 2.3C
Linking ideas
Each label line should have an appropriate written statement along it such as:
• When the liquid is heated it boils.
• When the liquid boils it starts to evaporate and becomes a gas.
• When a liquid is frozen it becomes a solid.
There are many different ways of making the links.
Credit learners with each accurate line drawn and relevant statement added.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
9
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 2.4A
Particles in the water cycle
1
The particles of water in the glacier are packed tightly together. They are arranged in regular rows
with particles touching one another. They are in fixed positions and cannot change places. The
particles can vibrate. The more energy the particles have, the more they can vibrate. Credit any
suitable drawings. The particles should be shown all the same size and every one must be touching the
ones alongside.
2
When the particles of water in the icebergs have energy transferred to them, they vibrate more and
more. Eventually they have enough energy to break away from the strong forces holding them in their
fixed places. The particles slide past one another and the iceberg melts.
3
When the particles of water in the sea have more energy transferred to them, they move more rapidly
and can overcome the weak forces holding them in place. Some of the particles escape into the
atmosphere and they evaporate into the air. The particles are far apart from one another and move
about freely, the water particles are now a gas.
Worksheet 2.4B
Particles in the water cycle
1
The particles of water in the glacier are packed tightly together. They are arranged in regular rows
with particles touching one another. They are in a fixed position and cannot change places. The
particles can vibrate. The more energy the particles have, the more they can vibrate.
When the particles of water in the icebergs have energy transferred to them, they vibrate more and
more. Eventually they have enough energy to break away from the strong forces holding them in their
fixed place. The particles slide past one another and the iceberg melts.
Credit any suitable drawings. The particles should be shown all the same size and every one must be
touching the ones alongside it.
2
An increase in the temperature will speed up this process because there will be more energy available
to be transferred to the water particles.
3
When the particles of water in the sea have more energy transferred to them, they move more rapidly
and can overcome the weak forces holding them in place. Some of the particles escape into the
atmosphere and they evaporate into the air. The particles are far apart from one another and move
about freely, so the water particles are now a gas. Credit any relevant diagrams.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
10
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
4
An increase in the temperature will speed up this process because there will be more energy available
to be transferred to the water particles, so they can escape the surface of the ocean and evaporate.
5
As the particles reach the clouds, the temperature decreases and the particles begin to condense. The
particles lose energy, which is transferred to the environment, they can no longer move about rapidly
and freely. The particles form a liquid and the particles are again touching one another, but they can
slide past one another. The particles now form a liquid. When the drops become too heavy to be held
in the clouds, they fall as rain. Credit any relevant diagrams.
Worksheet 2.4C
Particles in the water cycle
1
The particles of water in the glacier are packed tightly together. They are arranged in regular rows
with particles touching one another. They are in fixed positions and cannot change places. The
particles can vibrate. The more energy the particles have the more they can vibrate.
Credit any suitable drawings. The particles should be shown all the same size and every one must be
touching the ones alongside it.
When the particles of water in the icebergs and glaciers have energy transferred to them they vibrate
more and more. Eventually they have enough energy to break away from the strong forces holding
them in their fixed places. The particles slide past one another and the iceberg and glaciers melt.
When the particles of water in the sea have more energy transferred to them, they move more rapidly
and can overcome the weak forces holding them in place. Some of the particles escape into the
atmosphere as they evaporate into the air. The particles are far apart from one another and move about
freely; the water particles are now a gas.
As the particles reach the clouds, the temperature decreases and the particles begin to condense. The
particles lose energy, which is transferred to the environment, and they can no longer move about
rapidly and freely. The particles form a liquid and the particles are again touching one another, but
they can slide past one another. The particles now form a liquid. When the drops become too heavy to
be held in the clouds, they fall as rain.
Credit a full account of each stage and any relevant diagrams.
2
As the average global temperatures rise, more glaciers will melt and cause icebergs to form as the
particles in the solid ice have enough energy transferred to them to allow them to melt. This rise in
liquid water will cause sea levels to rise and cause flooding in low-lying countries. As the
temperatures increase it will also increase the amount of evaporation and, therefore, the amount of
rain will increase. This may also result in flooding.
Credit any logical explanation and reasoned argument.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
11
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 2.7A
Air is a mixture
1
Nitrogen
2
Oxygen
3
Carbon dioxide
4
Argon is used in light bulbs because it will not react with the hot filament.
5
The percentage of water vapour in the air changes because of the weather.
Worksheet 2.7B
What’s in the water?
1
Brand B
2
Brand A
3
Magnesium, sodium, bicarbonates and sulfates
4
Nitrates, iron and aluminium
Worksheet 2.7C
Comparing what’s in the water
1
These items are listed because they can be harmful at higher levels. People who buy this product want
to know that these items are present at only very low levels and that the water is safe to drink.
2
Credit the correct use of a bar chart. Bars for the same mineral in each brand of water should be
alongside one another, with a space between pairs and clearly labelled.
Worksheet 3.1A
Going to the Moon
1

2

3

4

5

Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
12
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 3.1B
Weight and mass on the Moon
1
55 × 10 = 550 (N)
2
55 kg
3
55 × 2 = 110 (N)
4
55 kg
5
20
= 10 (kg)
2
Worksheet 3.1C
Explaining changes on the Moon
1
 Reason: The strength of gravity on the Moon is less.
2
 Reason: Mass is not affected by gravity.
3
 Reason: The same objects will feel lighter as there is less gravity on the Moon.
4
 Reason: There is less gravity to pull the ball back down.
5
 Reason: The strength of gravity is less on the Moon, so the rocket will need less force to take off.
Worksheet 3.2A
Ideas of how the Solar System began
1
An hypothesis
2
A way to represent something that is difficult to see
3
A limitation
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
13
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 3.2B
Supporting or contradicting ideas
1
Supports
2
Contradicts
3
Supports
4
Supports
5
Supports
Worksheet 3.2C
Why use models?
1
Any two from:
• Takes too long to observe.
• No one was there to observe how the Solar System formed.
• Cannot do an experiment to test the hypothesis.
• Can change variables easily.
2
The model does not fully represent reality; something the model cannot show.
3
Orbits of planets/orbits of moons/sizes of planets/phases of the Moon etc.
Worksheet 3.4A
What are tides?
1
a
The forces that cause tides are called tidal forces.
b The forces that cause tides come from the Sun and the Moon. (can be in either order)
2
c
The forces are pulling forces known as gravity.
a
True
b True
c
False
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
14
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 3.4B
What are tidal forces?
1
a
The Sun and the Moon.
b Causing the depth of the sea/oceans to change/to increase and decrease.
Causing the height of the land above sea level to change.
c
Yes; because the Earth will exert a force of gravity on the rocks of the Moon.
Worksheet 3.4C
Changing tidal forces
1
Drawing of Earth, Moon and Sun or Moon, Earth and Sun in a line (not Earth, Sun, Moon).
Idea that gravity from the Sun and Moon add together to produce a larger force when all three objects
are in line.
2
The tidal force will be larger because the force of gravity from all four moons will add together/pull in
the same direction.
3
As the comet gets closer to the planet, the tidal force becomes too strong.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
15
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 3.6A
Getting faster
1
When Marcus lifts the toy car up onto the ramp, he gives the car gravitational potential energy.
2
As the car goes down the ramp, gravitational potential energy gets changed to kinetic energy.
3
When the car gets to the bottom of the ramp, the car has the most kinetic energy.
4
There will be more gravitational potential energy, so there will be more kinetic energy.
Worksheet 3.6B
Moving down a ramp
1
As the toy car goes down the ramp, it gets faster. The idea that the car has (more) gravitational
potential energy at the top of the ramp and that this gets changed to kinetic energy.
2
Make the ramp higher (not simply steeper – must have idea of increasing height). This creates more
gravitational potential energy to change to kinetic energy.
Worksheet 3.6C
Investigating energy changes
1
a
To ensure a fair test.
b Independent: height of the ramp
Dependent: the speed of the toy car
c
A and C or B and D because they are the same height, they provide the same gravitational
potential energy and therefore the same kinetic energy.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
16
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheets 4.1A, B and C
Living, non-living and dead
For all Worksheets, answers will depend entirely on what learners find, or the objects that you supply to
them. Some common examples might be:
Living: any plant or part of a plant, any animal or a fungus.
Was once alive, but is now dead: any dead organism, or part of an organism, or any material that has
been made from a living thing, such as leather (made from animal skin), paper, wood (both made from
trees), a food (made from an animal or a plant), cotton, silk or woollen cloth.
Has never been alive: stones, glass, plastic (although some learners may argue that this is made from
fossil fuels, which were made from living things – this illustrates how these categories are not always
absolutely clear-cut), air, water.
Learners using Worksheet 4.1C are also asked to explain why they have classified each object. Accept
any answers that indicate that they have thought carefully about this, and have used a systematic approach
in making their classifications.
Worksheet 4.3
A lost world
Look for these features in the stories or diaries.
All learners should:
• Write at least four sentences that relate to the task.
• Use the word ‘species’ correctly.
In addition, most learners should:
• Write an easily understood account of what they expected to find on Mount Lico and how they got to
the top.
• Explain how they would decide if an animal belonged to a new species, with reference to not being
able to breed successfully with other species.
In addition, some learners will:
• Write an engaging and interesting account of their role in the expedition.
• Use extra information obtained from research in their account.
• Discuss the difficulties of deciding if an animal belongs to a new species.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
17
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheets 4.5A, B and C
Writing a key to identify four teachers
Look for the following features in the keys for 4.5A and 4.5B:
• Each of the first three boxes contains a question and the last four boxes contain the names of the
teachers.
• Each question splits the teachers into two groups.
• Each question has a definite yes/no answer.
• The key works and can be used by anyone to identify the four chosen teachers.
Learners using Worksheet 4.5C could use the same style of key as shown on Worksheets 4.5A and B or
they could use the style that consists of paired statements to choose between. For both styles, check that:
• A sensible reason is given for the choice of style.
• Features have been chosen that can be easily used to separate the teachers into groups.
• A good reason is given for the choice of those features – for example, there are clear and distinct
differences between the teachers that can easily be identified.
• The key works and can be used by anyone to identify the four chosen teachers.
Worksheet 5.2A
Temperature scale
1
Check learners have correctly marked: B at ‒30°C on the scale; C at 0°C on the scale.
2
Check learners have correctly marked: D at 10°C on the scale.
3
Check learners have correctly marked: E at ‒10°C on the scale.
4
‒70°C
5
Check learners have correctly marked: F at −70°C on the scale.
6
‒20°C
7
Check learners have correctly marked: G at ‒20°C on the scale.
Worksheet 5.2B
Melting points
1
330.2°C
2
99.2°C
3
1062.8°C
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
18
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
4
117.4°C
5
−219.2°C
6
109°C, it was much lower than the others.
7
a
± 1.2°C
b ± 0.2°C
c
± 2.2°C
8
Temperature in °C
Temperature in °C corrected to one decimal place
63.51
63.5
37.48
37.5
‒14.83
‒14.8
4.233
84.03
4.2
84.0
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
19
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 5.2C
Melting point data
1
Time in minutes
Mean temperature in °C
0
21.4
10
201
20
321.8
30
453.5
40
529.2
50
603.2
60
660.6
70
660.4
80
664.0
2
The graph should be drawn with a sharp pencil and a ruler. Axes should be labelled. Look carefully at
the temperature scale on the y-axis as the scale cannot be large enough to allow plotting the mean
temperatures accurately to 1 decimal place. Pay attention to the reading at 30 minutes as there is an
anomalous result (421°C) that should be ignored when calculating the mean. Credit accurately plotted
points that are joined appropriately.
3
Credit any meaningful description, such as: as the time increases, the temperature increases; the temperature
increases quickly at the start, but between 60 and 80 minutes there is almost no change in temperature.
Learners should make reference to specific times and temperatures when describing the graph.
Worksheet 5.2D
Comparing metals and non-metals
Answers will depend on what the learners find out.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
20
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 5.2E
Comparing metals and non-metals
Answers will depend on what the learners find out.
Worksheet 5.2F
Comparing metals and non-metals
Answers will depend on what the learners find out. However, the point of this worksheet is for learners to
practise the use of comparative language. Look out for any meaningful contrasts and/or comparisons that
are made between a metal and a non-metal.
Worksheet 5.6A
Acids, alkalis and indicators
Acid – turns litmus red
Indicator – changes colour to show if a solution is an acid or an alkali
Alkali – turns litmus blue
Neutral – neither acid nor alkali
Corrosive – can destroy living tissue
Worksheet 5.6B
Acids, alkalis and indicators
Answers will depend on which words learners decide to link. You should look for sentences that link the
items included, such as the example given on the worksheet: Litmus is an indicator – it changes to a
different colour in an acid and an alkali. Sentences need only include two of the words from the list.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
21
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 5.6C
Acids, alkalis and indicators
1
Accept any three acidic foods, such as lemons, vinegar, coffee, cola.
2
Accept any three, such as toothpaste, soap, toilet cleaner, bleach.
3
The hazard symbol for harmful to health should be drawn.
4
If an indicator solution such as litmus is added to the two beakers, you will be able to tell them apart
because the litmus will turn red in the acid and blue in the alkali. Credit appropriate colour changes
with other indicators.
5
Credit any correct properties, such as: acids turn litmus red (or universal indicator yellow/red) and
they have a sharp/tangy/sour taste.
6
The properties of acids are different from alkalis as alkalis turn litmus blue (or universal indicator
blue/purple). Acids do not have a soapy feel like alkalis.
7
Litmus and universal indicator can both show if a solution is an acid, an alkali or neutral. However,
universal indicator solution can show if a solution is a strong or weak acid or alkali because it changes
to a range of different colours.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
22
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 6.2A
Echoes
1
Push and pull/towards and away from her.
2
a
A reflected sound wave.
The same type of sound as the original clap, but quieter than the original clap.
3
One straight arrow from dolphin (any part) to fish.
One straight arrow from fish to dolphin (any part).
Arrows must touch the fish at the same point.
Worksheet 6.2C
Echoes
1
speed
a=
(750 × 2)
= 1500 m/s
1.0
Give partial credit if the distance is not doubled.
b Particles in a liquid are closer together (than in a gas); vibrations in the sound wave are passed on
more easily in a liquid.
Worksheet 6.4A
Plate tectonics
1
a
Tectonic plates
b The plates sit on liquid; movement in the liquid/layer below; heat from the core.
2
a
(solid) rock
b Mantle
c
Similarity – the crust and mantle are both made from rock.
Difference – the crust is solid and the mantle is liquid.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
23
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 6.4C
Plate tectonics
1
a
Plates pushing together/pushing in opposite directions (not moving in opposite directions as could
be apart); rocks are pushed up.
b Plates moving in different directions; pressure/friction between plates (causes sudden movement).
c
Movement of plates; causes openings in the crust; magma can escape.
Worksheet 6.5A
Eclipses
1
a
Solar (eclipse)
b The Moon blocks the light from the Sun/the shadow of the Moon falls onto the Earth.
2
c
The Moon is moving/orbiting the Earth; the shadow of the Moon is moving (across the Earth’s
surface).
a
The shadow of the Moon is (relatively) small/smaller than Earth; the shadow of the Moon does not
cover the whole Earth.
b It could cause permanent eye damage/blindness.
3
a
Lunar (eclipse)
b Earth, Moon (first row ticked)
Worksheet 6.5C
Eclipses
1
a
Two reasons from:
Eclipses occur in different places.
The shadow of the Moon may not fall onto the Earth/may miss the Earth.
The Earth, Moon and Sun are not exactly on the same level/same plane/do not lie in a straight line
every lunar month.
b The Moon is not always the same distance from the Earth; when the Moon is closer to Earth, less
of the Sun can be seen/when the Moon is further from the Earth, more of the Sun can be seen.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
24
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheets 7.1A, B and C
Microorganisms vocabulary
1
An organism that is so small we can only see it with a microscope is called a microorganism.
2
Mushrooms and toadstools are examples of fungi.
3
Bacteria are single-celled microorganisms that have cells much smaller than animal cells or plant
cells.
4
One example of a single-celled fungus is yeast.
5
A group of microorganisms growing on agar jelly is called a colony.
6
When all the living organisms on something have been killed, we say that it is sterile.
7
Protozoa are single-celled microorganisms with cells like animal cells.
8
Single-celled microorganisms with cells like plant cells are called algae.
9
The plural of fungus is fungi.
10 The singular of bacteria is bacterium.
Worksheets 7.2A, B and C
Food web in a pond
1
2
Two
3
Five
4
The arrows show how energy flows through the food web.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
25
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 7.3A
Bacteria in milk
1
So that she can compare it with the milk that is heated. It is a control experiment.
2
There were lots of living bacteria in bottle A.
3
The dye will not change colour. It will stay blue.
Worksheet 7.3B
Bacteria in milk
1
So that she can compare it with the milk that is heated. It is a control experiment.
2
There were lots of living bacteria in bottle A.
3
The dye will not change colour. It will stay blue.
4
a
Bottle A.
b Bacteria in the milk have made it sour. They have decomposed the milk, changing some of it to acids.
5
All the bacteria in UHT milk have been killed, but only some are killed when milk is pasteurised.
Worksheet 7.3C
Bacteria in milk
1
So that she can compare it with the milk that is heated. It is a control experiment.
2
There were bacteria in bottle A, which made the dye in the milk change first to pink and then white.
There were no (or fewer) bacteria in bottle B, because they had been killed when the milk was heated,
so the dye did not change colour.
3
The bacteria in bottle A had changed some of the milk to acid. This made the pH lower than in normal
milk.
There were no (or fewer) bacteria in bottle B, so the milk stayed at its usual pH (or the pH did not fall
as low as in bottle A.)
4
All the bacteria in UHT milk have been killed, but only some are killed when milk is pasteurised.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
26
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 7.4A
Decomposers and plant growth
1
Whether or not the soil contains decomposers.
2
How much light the grass gets.
Whether the plants are in a glasshouse or outside.
The volume of water given to the grass plants.
3
Grass grows better when there are decomposers in the soil.
Worksheet 7.4B
Decomposers and plant growth
1
Whether or not the soil contains decomposers.
2
How much light the grass gets.
Whether the plants are in a glasshouse or outside.
The volume of water given to the grass plants.
The area of soil from which the grass is collected.
3
4
The results do support the hypothesis. The grass grown in the soil containing a lot of decomposers had
a greater mass than the grass grown in the soil where there were no decomposers.
5
They could repeat the experiment several more times. They could take samples of grass more often.
They could take samples from the soil and measure how many decomposers it contains.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
27
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 7.4C
Decomposers and plant growth
1
Whether or not the soil contains decomposers.
2
How much light the grass gets.
Whether the plants are in a glasshouse or outside.
The volume of water given to the grass plants.
3
The graph below shows the results for plot A and for plot B.
4
The results do support the hypothesis. The grass grown in the soil containing decomposers had a
greater mass than the grass grown in the soil where there were no decomposers.
5
Decomposers break down dead parts of plants and animals in the soil. This releases nutrients that
plants can use to grow.
Some learners may comment on the shapes of both graphs. For the first year, the grass in both plots
grows fast (the mass increases and the graph slopes upwards) as the young seedlings germinate and
grow to cover the soil. After one year, the rate of growth slows down, perhaps because the grass has
filled all the space available, and each plant has grown as big as it can. The mass in both plots then
remains fairly steady, with small ups and downs.
6
They could repeat the experiment several more times. This would allow them to spot any anomalous
results. They could calculate mean masses from all of the plots, instead of recording just one mass, at
each stage.
They could take samples of the grass more often. This would allow them to plot more points on the
graph, so they could be more certain of the patterns and trends shown by the lines.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
28
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
They could take samples from the soil and measure how many decomposers it contains. This would be
useful, because we cannot be sure that decomposers did not start to grow in the soil in plot B after a
while.
Worksheet 8.1A
Simple chemical reactions
1
Iron sulfide
2
Magnesium and oxygen
3
Oxygen and hydrogen
4
a
Hydrogen
b Magnesium chloride
5
Carbon dioxide
6
a
Hydrogen
b Zinc chloride
Worksheet 8.1B
Simple chemical reactions
Answers will depend on what the learners choose to link. Credit any sensible links, such as:
Magnesium combines with oxygen when it burns.
Oxygen gas is present in the air.
Worksheet 8.1C
Simple chemical reactions
1
Iron oxide
2
No. Accept partly correct. The nail in the tube with air dried by calcium chloride (B) has not rusted.
3
Accept any sensible suggestion. They should spot that water and air are needed to make the iron rust.
(Water is not part of the chemical reaction but needs to be present for the rusting to take place.) The
fact that there is water vapour in the air should be mentioned.
4
Accept any sensible suggestions, such as painting the nails or covering them in grease.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
29
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 8.2A
Choosing equipment
The following pieces of equipment should be circled:
burette, conical flask, clamp stand with boss, safety glasses, universal indicator solution, measuring
cylinder.
All pieces should be labelled.
Worksheet 8.2B
Neutralisation
1
Neutralisation is a reaction between an acid and an alkali where a solution of pH7 is produced.
2
Sodium chloride and water
3
The plan should include a list of equipment needed: burette, conical flask, clamp stand with boss,
safety glasses, universal indicator solution, measuring cylinder. It should also give a clear account of
how the equipment is used and step-by-step instructions. Credit a clear, labelled diagram. By using the
assessment grid learners can assess their partner’s work and focus on what they need to do to improve
their own work.
Worksheet 8.2C
Neutralisation
1
Zara should treat both solutions as if they are corrosive as she doesn’t know how strong the solutions
are. She should wear safety glasses and be very careful when measuring them out for her investigation.
2
The plan should include:
• A list of suitable equipment: burette, clamp stand with boss, conical flask, universal indicator
solution, dilute hydrochloric acid, measuring cylinder.
• A consideration of variables to keep the same: volume of sodium hydroxide solution used, same
volume of universal indicator solution added, same type and concentration of hydrochloric acid
used, same equipment used, same person spotting the end point, mixing the solution in the same
way after each addition of acid.
• A logical plan, which includes details of how the neutralisation should be carried out.
3
Solution Y is the strongest.
4
Zara knows this because it took much more dilute acid to neutralise solution Y than it took to
neutralise solution X.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
30
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
5
The bottle of solution X should have a harmful to health warning label on it. The bottle of solution Y
should have a corrosive label on it. It may make sense to be cautious and give both X and Y a
corrosive label.
6
Zara ignored the first attempt, which was much lower than the other two readings.
7
Zara could read this accurately on the burette because the scale is clear and she measured from the
bottom of the meniscus with her eye exactly in line with it.
8
She knew she had to stop adding more acid when the universal indicator solution turned green. Credit
any comments on how difficult it is to see the end point exactly.
9
Zara repeated her neutralisations to make sure her results were reliable. Credit any comments about
what may have gone wrong with the first attempt with solution X or any difficulties with carrying out
the investigation.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
31
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 8.3A
Investigating terms
Terms
Description
prediction
what you think will happen
variable
quantities that can be changed in an investigation
reliable
that the investigation can be repeated and produce the same or
similar answers
evidence
this is the information needed to support a theory, hypothesis
or prediction
fair test
taking account of all the variables so that you are only testing
one change in your investigation
data
the information you collect. It could be the thing you measure,
such as the temperature change or the meting point of a metal
conclusion
the explanation you give based on the information/evidence
you have
risk assessment
the thinking and planning you do to make sure that the
investigation is safe, and that you are aware of any dangers and
how to avoid them
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
32
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 8.3B
Investigation skills
1
The number of spatulas of powdered metal that they use.
2
The type of powdered metal, and the type, volume and concentration of acid should be kept the same.
Credit other comments about using the same equipment such as the timer.
3
Safety glasses, beakers, spatula, powdered metal, hydrochloric acid, measuring cylinder, timer. (Note:
do not credit test tubes due to the statement in the text.)
4
Graph should be drawn with a sharp pencil and ruler. Number of spatulas of metal used along the xaxis and time along the y-axis. Axes labelled and a suitable scale used. Points should be plotted
accurately and a suitable line of best fit drawn.
5
Their prediction was correct for the quantities of powdered metal used from one to six. However, the
results for adding seven and eight spatulas of metal to the acid show that the time does not increase.
So the prediction is only partly correct.
6
The graph shows that when more of the powdered metal is used, the time taken for the reaction to end
is shorter. The line of the graph is very steep at the start and then the line gets less steep and finally the
line is almost horizontal. This shows that the reaction increases in speed quickly when the amount of
powdered metal increases from one to two spatulas. The increase is less from two spatulas to three,
and slower again from four spatulas to five. Between six and eight spatulas, adding more powdered
metal makes no difference to the time taken for the reaction.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
33
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 8.3C
Investigation skills
1
The useful information was that the reaction caused so many bubbles that it overflowed the test tube,
so they knew that they had to use a larger container.
2
The detailed plan should include an equipment list, which covers: safety glasses, beakers, spatula,
powdered metal, hydrochloric acid, measuring cylinder, timer. (Note: do not credit test tubes due to the
statement in the text.) It needs to be clear that they are making the test as fair as possible by keeping the
volume, type and concentration of the acid the same. Credit all efforts to keep the test fair by using the
same timer, the same end point and so on. The method should be clear and able to be followed.
3
Number of spatulas
of powdered metal
added to 10 cm3
hydrochloric acid
Time for all bubbles to stop in seconds
1st attempt
2nd attempt
3rd attempt
Mean
1
102
98
99
99.7
2
62
60
59
60.3
3
43
42
45
43.3
4
29
34
26
29.7
5
18
16
20
18
6
12
11
12
11.7
7
13
12
12
12.3
8
12
12
12
12
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
34
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
4
Graph should be drawn with a sharp pencil and ruler. The mean number of spatulas of powdered
metal used should be plotted along the x-axis and time along the y-axis. Axes labelled and a suitable
scale used. Points should be plotted accurately and a suitable line of best fit drawn.
5
The line of the graph is steep at the start, then gets less steep and finally flattens out so that it is
almost horizontal.
The graph shows that when more of the powdered metal is used, the time taken for the reaction to end is
shorter. This shows that the reaction increases in speed quickly when the amount of powdered metal
increases from one to two spatulas; the change in time is from almost 100 seconds to 60 seconds. The
increase is less from two spatulas to three; the time changes from 60 seconds to 43 seconds. It is slower
again from four spatulas five; 30 seconds to 18 seconds. Between six and eight spatulas, adding more
powdered metal makes very little or no difference to the time taken for the reaction to end.
Learners should make reference to the actual figures from the graph.
6
Their prediction is correct for quantities of powdered metal used from one to six spatulas. Over this
range of numbers of spatulas added, there is a decrease in the time taken for the reaction to be
completed. However, the results for adding seven and eight spatulas of metal to the acid show that the
time does not increase. So, the prediction is only partly correct.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
35
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 9.1A
What is current?
1
Positive (terminal)
2
Electrons are small particles with a negative charge.
3
a
Arrow can be anywhere on diagram, but must point away from the labelled end of the wire, i.e., to
the left.
b i
ii
Gets faster
Gets slower
iii Stops or vibrate randomly
Worksheet 9.1C
What is current?
1
a
Copper does not have the most electrons (in the Table); easiest for electrons in copper to
move/easier for the electrons to move than the other substances in the Table. (Accept suggestion
that fewer electrons move in lead.)
b Lead has the most electrons (in the Table); hardest for electrons in lead to move/harder for the
electrons to move than the other substances in the Table. (Accept suggestion that fewer electrons
move in lead.)
Worksheet 9.2A and B
Circuit symbols and diagrams
1
a
+ next to long line; − next to short line
b
c
Wires/leads
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
36
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
2
a
b
Worksheet 9.2C
Circuit symbols and diagrams
3
a
b A circuit diagram is quicker to draw, uses standard symbols, avoids confusion when the same type
of components do not look the same, and allows the circuit to be seen more clearly.
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
37
CAMBRIDGE LOWER SECONDARY SCIENCE 7: WORKSHEET ANSWERS
Worksheet 9.3A and B
Understanding current
1
a
b 1.0 A or 1 A (must include unit)
Extension sheet
2
a
Decrease
b Increase
c
Stops
d Plastic is an insulator; insulators inhibit the flow of electrons/do not allow electrons to flow.
Worksheet 9.3C
Understanding current
1
a
Insulator
b Insulators inhibit the movement of electrons/do not allow electrons to flow.
c
To stop current from flowing to the pylon/away from the wire.
d FEC
Cambridge Lower Secondary Science 7 – Mary Jones, Diane Fellowes-Freeman and Michael Smyth © Cambridge University Press 2021
38