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Checkpoint Science Revision Guide Answers final

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Cambridge Checkpoint Science Revision Guide Second
Edition for the Cambridge Secondary 1 Test
Chapter 1 answers
Activity 3
a) For example: As water transpires/evaporates from the leaves, the coloured water is transported up the
celery stalk through the xylem into the leaves. This turns the leaves a different colour.
b) For example: It shows the xylem vessels, which have been stained by the coloured water.
c) For example: It shows the coloured water in the xylem.
Activity 4
For example: If the leaves are taken off the celery in the red water, there will be no
transpiration/evaporation from the leaves and less water drawn up the celery. Accept comments referring
to volume, such as: The volume of red water left in the container will be greater at the end of the
experiment than the volume of blue water.
Activity 5
For example:
Activity 7
For example:
1
The amount of water in the body needs to be kept stable.
2
We take in water in food and drink.
3
We lose water through sweating, breathing and urinating.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
Edition for the Cambridge Secondary 1 Test
4
The kidneys filter waste from the blood.
5
The kidneys are part of the renal system.
Activity 8
a) kidney
b) ureter
c) bladder
d) urethra
Activity 9
The correct definition for each term is as follows:
nephron
A filter that removes urine
ureter
A tube from each kidney that carries urine to the bladder
renal vein
Carries cleaned blood back to the heart
renal artery
Carries blood from your heart to your kidneys
Activity 10
For example:
Model Part of the renal system
A
Kidneys
B
C
How it is represented in the model
Plastic bottles with filter paper
Bladder
Filter funnel
Ureters
Clear tubing
Body/heart
Plastic bottle
Kidneys
Purple shapes
Renal artery and vein
Ureters
Bladder
Body/heart/liver
Blue and red shapes
Plastic tubing
Yellow shape
Plastic box
Renal arteries
Tubing into kidneys at top
Kidneys
Sponges
Ureters
Tubing from each kidney at bottom
Bladder
Green box
Urethra
Tap at bottom
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
Edition for the Cambridge Secondary 1 Test
Activity 11
For example:
Model
A
B
C
Positive
Shows the three main
parts of the system
(kidneys, ureters and
bladder)
Shows more detail and
uses different colours to
represent different
parts
Detailed and it uses
sponges to suggest how
blood can be filtered
through the kidneys
Minus
Less detail than the
other models
Interesting
The way filter paper has been
used to show a filtering system
Could have shown the
renal artery going into
each kidney and renal
vein coming from each
kidney back to heart
Could have shown the
renal artery going into
each kidney and renal
vein coming from each
kidney back to heart
Colours make the different
parts of the model stand out
and it is 3D
Use of tap at the bottom of the
urinary system suggests being
able to control going to the
toilet to urinate
Activity 12
For example: C is the best model because it shows renal arteries going into each kidney and the sponges
have holes in, which models filtering inside the kidneys. A ureter is shown going from each kidney to the
bladder, and the tap at the end of the system models the idea that humans can control when they urinate.
It does not have labels, so you have to use your knowledge to work out which part is which.
Revision test answers
1
nephron
2
B
3
true; false; true; false; true
4
a) Xylem – cells that form long tubes that transport water and nutrients from the roots
up the stem to the leaves
b) Nephron – a tiny tube that helps filter the blood in the kidneys
c) Urea – a toxic waste substance filtered out of the blood by the kidneys
5
For example: Renal arteries carry unfiltered blood from the heart to the kidneys, while the renal veins
take filtered blood back to the heart.
6
For example: Both flowering plants and human kidneys are included because both have systems that
transport water. In plants, the water is transported from the root hairs through the xylem to the rest of
the plant. In humans, the kidneys filter the blood and get rid of excess water.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
Edition for the Cambridge Secondary 1 Test
7
a), b)
8
a)
b)
c)
d)
renal artery
kidney
ureter
bladder
Chapter 2 answers
Activity 1
The order of the scientists in the timeline should be:
A
Joannes Baptista van Helmont (1580–1644)
B
Stephen Hales (1677–1761)
C
Jan Ingenhousz (1730–1799)
D
Joseph Priestley (1733–1804)
E
Antoine Lavoisier (1743–1794)
Activity 2
The ideas developed by each scientist are as follows:
Joseph Priestley
A gas produced by plants allows things to burn in it.
Antoine Lavoisier
The gas produced by plants is named oxygen.
Jan Ingenhousz
Plants take up carbon dioxide.
Stephen Hales
Air helps plants to survive.
Joannes Baptista van Helmont Water is a basic requirement for life.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
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Activity 3
a) Van Helmont investigated how watering a willow tree affected its mass. His results suggested that
plants only needed water for growth. This was incorrect, but it did lead to other scientists checking his
idea.
b) Hales discovered that plants needed a ‘portion of air’ to survive, adding to scientists’ understanding of
what plants need to live and grow.
c) Jan Ingenhousz showed that green plants take up carbon dioxide from the air when they are put in the
light.
d) They would have discussed Priestley’s experiment, where he put a mint plant in a jar of carbon dioxide
and let sunlight shine on it. Priestly shared his discovery that the gas appeared to change to one that
allowed things to burn in it. It was Lavoisier who named the gas oxygen.
e) Plants take in carbon dioxide and give out oxygen when they photosynthesise. Animals, including
humans, need oxygen to survive. Without plants, humans and other animals would not be able to live.
Activity 4
a) a) boiling ethanol; b) hot water; c) leaf; d) Bunsen burner turned off
b) Ethanol dissolves the chlorophyll and removes the green colour from the leaf.
c) chlorophyll
d) blue/black
e) glucose
f) Within the chloroplasts is chlorophyll, which traps light energy to convert carbon dioxide and water into
glucose and oxygen.
Activity 5
For example:
1
Describe what the starch test is testing.
2
Use scientific language: starch; iodine solution; blue/black; result; leaves; ethanol; boiling.
3
Describe safety procedures/risk assessment.
4
State the result and what it shows.
Activity 6
a) To ensure that any starch present at the end of the experiment was produced during the experiment.
b) For example: type of plant; size of plant; number of leaves; plastic bag over each plant; plants left in the
same place; plants left for the same length of time; plants watered the same amount.
c) To ensure that both plants were exposed to light so photosynthesis could take place.
d) Learners will need to check if starch is present.
e) A leaf from the plant with soda lime/without carbon dioxide will not contain any starch. A leaf from the
plant with sodium hydrogencarbonate/enriched with carbon dioxide will contain starch. Carbon dioxide
is needed for photosynthesis/starch production.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
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Activity 8
a) They were trying to prove that light is needed for photosynthesis.
b) Photosynthesis is taking place in Plant A because it is exposed to light, which is needed for
photosynthesis. Plant B is in the dark, so photosynthesis cannot take place.
c) Place a glowing splint inside the tube of gas collected and see if it re‐ignites.
d) water + carbon dioxide ⎯⎯⎯⎯⎯⎯ carbohydrate + oxygen
Activity 9
a) Examples of strengths:




Part of the question is used in the answer.
They know photosynthesis can take place over 24 hours.
They state that more glucose will be produced.
They link glucose to energy and making cellulose.
b) Examples of weaknesses:


It does not give the photosynthesis equation.
It does not link to solving problems, e.g. need for more food, reducing food miles, being able to
produce crops all year and in urban spaces.
c) Example of a re‐written answer: Farmers grow some crops – such as tomatoes, cucumbers and sweet
peas – indoors, using special lights that are kept on 24 hours a day. This means that plants can
photosynthesise day and night, so they can produce more glucose for energy and to make cellulose and
starch. This means that crops can grow more quickly and keep growing in the winter months when
there is less sunlight. This is important because the population has grown, so more food is needed, and
it reduces food miles as it means that crops can be grown in urban areas not just farmland.
Activity 10
Learner A’s answer: 1 mark
For example: The answer only includes ‘plants need carbon dioxide’ (1 mark).
Learner B’s answer: 3 marks
For example: Uses first part of the question (1 mark), states that plants need CO2 (1 mark) for
photosynthesis (1 mark).
Learner C’s answer: 5 marks
For example: Uses part of the question (1 mark), states that plants need CO2 (1 mark) and its role in
photosynthesis (1 mark). Includes the equation for photosynthesis (1 mark) and explains that food
production will be increased (1 mark).
Activity 11
Suggested question could be: Explain why some growers place CO2 pipes near the leaves of plants.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
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Activity 12
Leaves need chlorophyll to photosynthesise. If a plant has variegated leaves, it is only the green parts with
chlorophyll that can photosynthesise. The areas that are not green have no chlorophyll and do not
photosynthesise.
Activity 13
Plant A Starch would be present in the whole leaf because the whole of each leaf is green, contains
chlorophyll and can photosynthesise.
Plant B Starch would not be present in the whole leaf because only the green parts contain chlorophyll and
can photosynthesise. The parts that are not green would not contain starch because they do not contain
chlorophyll, so cannot photosynthesise.
Revision test answers
1
B
2
D
3
carbon dioxide + water ⎯⎯⎯⎯⎯⎯ carbohydrate + oxygen
4
Carbon dioxide and water react using energy from sunlight to produce carbohydrate and oxygen.
5
Examples could include the amount of light, carbon dioxide concentration, temperature, etc. Accept
amount of water.
6
1
Heat leaf in boiling water for 30 seconds to kill leaf and stop photosynthesis.
2 Boil ethanol in a water bath and add the leaf to the ethanol for a few minutes to remove the green
colour (so it is easier to see the colour change).
3 Wash the leaf with water to soften it, then spread it on a white tile (so it is easier to see the colour
change).
4 Add iodine solution to the leaf using a pipette.
Result: The parts of the leaf that contain starch turn the iodine from brown to blue/black.
7
If non‐green areas turn green, more of the leaf now contains chlorophyll, so more of the leaf can
photosynthesise. This means more glucose for growth can be produced by photosynthesis.
8
a) A graph to show the amount of carbon dioxide absorbed by a plant over 24 hours
b) Photosynthesis is at its peak at 12 noon. This is when the most carbon dioxide is absorbed, because
the Sun is at its highest so the most light energy is available.
c) The position of the sun changes and so the amount of light energy for photosynthesis decreases
through the afternoon. Photosynthesis slows down, so less carbon dioxide is absorbed.
d) approximately 9 g/h
e) Oxygen is produced.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
Edition for the Cambridge Secondary 1 Test
Chapter 3 answers
Activity 2
a) Graph A shows continuous data. A line graph is used because there is a continuous range of values.
b) Graph B shows discontinuous data. A bar graph is used because there are (four) discrete conditions.
Activity 3
Variation
skin colour
height
foot length
hair colour
blood group
ear piercing
Genetic





Environmental Continuous data







Discontinuous data




Activity 5
nucleus; chromosome; DNA strand; gene
Activity 6
a) Male, because the two sex chromosomes look different so are XY.
b) Two chromosomes of the same size should be drawn in the space.
Activity 8
Text
Image
A
2
B
5
C
6
D
1
E
3
F
4
Activity 9
Top row: Bb (brown eye) and Bb (brown eye)
Bottom row: bb (blue eye) and bb (blue eye)
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Cambridge Checkpoint Science Revision Guide Second
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Activity 10
The pictures of the beaks should show a gradual change from a short, stubby beak to a long, thin, pointed
beak.
Activity 11
For example: Tortoises usually have domed shells like Tortoise A, but Tortoise B lives on an island with
shrubs and low trees. This means that its main food is leaves from the shrubs and trees. Some tortoises
might have had a shell that was slightly higher at the front, meaning they could reach higher for leaves to
eat. This gave them an advantage, as they could find more food. They passed this trait to their offspring
and they in turn passed it on via their genes. The front part of the shell therefore changed/evolved to allow
the head and neck to reach for leaves on trees and shrubs more easily.
Activity 12
Answer A: 2 marks – mentioned genes for long beaks and offspring inheriting.
Answer B: 6 marks – mentioned variation (1 mark), birds with beaks suited to environment (1 mark), had
offspring that inherited genes (1 mark), adaptation over time (1 mark), adaptations are genetically
inherited (1 mark), birds that did not adapt became extinct (1 mark).
Activity 13
Aristotle – 5
Mendel – 2
Darwin – 4
Rosalind Franklin – 1
Crick and Watson – 3
Revision test answers
1
A
2
B
3
For example: Continuous data is where measurements have been taken, e.g. in grams or centimetres.
Discontinuous data is usually counting whole numbers of things that have discrete values or groups,
such as eye colour, shoe size or people with scars.
4
Genetic variation: blood group; eye colour
Both: hair colour; height; skin colour
Environmental variation: tattoos; scars; ear piercing
5
23 pairs/46 chromosomes
6
DNA
7
XX
8
XY
9
For example, any two from:
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
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•
Different traits can be passed on to offspring.
•
Inherited factors can be predicted.
•
Each factor has two sets of instructions, one from each parent.
•
There are dominant characteristics.
•
There are recessive characteristics.
10
B
B
b
Bb
Bb
b
Bb
Bb
11 For example: Darwin observed that organisms show variation and have different traits depending on
the environment they live in. Traits can be passed on through the genes to organisms’ offspring, and
this is known as genetic inheritance. Gradually, over thousands of years, new species result from
evolution. Species that are not well adapted gradually die out and become extinct.
Chapter 4 answers
Activity 1
a) placenta
b) umbilical cord
c) fetus
d) uterus
Activity 2
The umbilical cord is sometimes called the lifeline because it carries blood back and forwards from the
mother to the fetus. It carries nutrients and oxygen from the mother’s placenta to the fetus and then
carries waste material back in the opposite direction.
Activity 3
Answer 1: 1 mark
For example: Mentioned harming the baby, so 1 mark, but did not explain how this can happen.
Answer 2: 2 marks
For example: Includes that harmful chemicals from smoke and drink pass through the umbilical cord to the
fetus.
Answer 3: 4 marks
For example: States what affects the fetus (1 mark), describes how these things can go through the
mother’s bloodstream (1 mark), placenta and umbilical cord (1 mark) to the fetus (1 mark).
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Cambridge Checkpoint Science Revision Guide Second
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Activity 5
For example: There is a difference between the infant mortality rates in Afghanistan and Monaco because:
•
Afghanistan has suffered war. It is a poor country, so hospitals have less equipment and mothers may
not get enough food to stay healthy. Many live in poverty and are at risk of catching diseases, and there
is a shortage of health workers.
•
Monaco is a small country. It is wealthy, so poverty is low and hospitals are well equipped.
Activity 6
For example: Cigarettes contain over 4000 different chemicals, and many are toxic (poisonous). If you keep
smoking during pregnancy, the chemicals can be passed through the placenta and then the umbilical cord
to your baby. This may harm your baby: they could be stillborn, premature, have a low birth weight or have
birth defects.
Activity 7
Prescribed and recreational drugs pass into the pregnant woman’s bloodstream. Some substances pass
through the placenta to the umbilical cord and into the blood of the fetus. The liver of the fetus is not able
to process the drugs and the baby could be born premature, underweight or stillborn.
Activity 8
a) lungs
b) spinal cord and brain
c) liver
Activity 9
For example:
•
Video – could be eye catching and interesting.
•
Face to face – allows mothers to ask questions that are relevant to themselves.
•
Directing to helpful websites – give a range of information and mothers can access them in private.
•
Text messages or social media apps (e.g. Facebook, Twitter) – lots of pregnant women communicate
using their mobile phones, so they could get information quickly to lots of women and keep them up to
date.
•
Leaflets given when women find out that they are pregnant – they can keep the leaflets and look at
them often. Leaflets could provide information about other organisations to contact.
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Activity 10
Technology
Purpose
air filter
For example: Cleans air to get rid of harmful particles
oxygen saturation
monitor
For example: Checks oxygen levels in the blood
temperature sensor
For example: Senses if neonate’s temperature is too low
ventilator
For example: Helps neonate to breathe
portholes
For example: Allow people to touch neonate without passing on
germs
vital signs monitor
For example: Checks neonate’s heart is beating properly
Activity 11
‘Neo’ means new and ‘natal’ means relating to birth, so neonate means newborn.
Revision test answers
1
A
2
C
3
false; false; true
4
a) For example: A newborn baby
b) For example: Tube taking blood with nutrients and oxygen from the mother’s placenta to the fetus
and taking waste away
c) For example: A baby born before 37 weeks of pregnancy
5
For example, any four of the following: low birth weight, pneumonia, brain damage, blindness,
deafness, hepatitis, meningitis, stillbirth
6
For example: Chemicals from cigarettes get into the pregnant woman’s bloodstream. They pass through
the placenta to the umbilical cord and so the chemicals get into the blood of the fetus.
7
For example: A neonate might be placed in an incubator because they were premature (born before 37
weeks), underweight or have an illness/disease.
8
Any three of the following:






Air filter: Cleans air of particles that might harm the neonate
Oxygen saturation monitor: Monitors oxygen level in neonate’s blood
Temperature sensor: Monitors neonate’s temperature
Ventilator: Helps neonate breathe/gives oxygen
Portholes: Allow parents / healthcare workers to touch neonate without passing on germs
Vital signs monitor: Monitors heart
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Cambridge Checkpoint Science Revision Guide Second
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Chapter 5 answers
Activity 4
Example answers in the double bubble diagram:
•
Similarities in the centre hexagons: for example, recorded notes, used a camera, observed over time,
observed animals, collected data, noted observations.
•
Differences in left‐hand bubbles for learners: for example, studied plants / did not study chimpanzees;
worked around their school; observed over weeks, not years; did not work with other people.
•
Differences in right‐hand bubbles for Jane Goodall: for example, studied chimpanzees / did not study
plants etc.; worked in Tanzania; observed the same chimpanzees over decades; worked with local
people.
Activity 5
a) Multiplied by 100
b)
Plant or animal and their food
(if animal)
Number in 1 m2
quadrat
Estimated number
in 100 m2 area
grass clumps
18
1800
worms
(eat dead plant material)
2
200
rove beetles
(eat beetle larvae, aphids
and small caterpillars)
7
700
dandelions
6
600
ants
(attracted to sweet and
sugary foods)
100
1000
caterpillars
(eat leaves)
1
100
Activity 6
a) For example: They may have found more ants in the quadrat at 3 p.m. because the learners ate their
lunches outside, so they might have left sweet/sugary crumbs that attracted the ants.
b) Either observation over time, because the students are collecting data from observations across the
school day, and/or pattern seeking, because the students are collecting data to find a pattern across
the day.
c) Limitations could include: only using one quadrat, which might have been placed on an area which was
not typical of the whole field; only collecting data on one specific day and at one time.
Suggested improvements could include: Survey more than one part of the school field (e.g. using 10
quadrats in different parts of the field); repeat the data collection at different times of day and on
different days for a week or month.
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Activity 7
There were few starlings (5) or sparrows (3) at 9 a.m. At 1 p.m. the numbers increased to around five times
as many birds for both species. At 3 p.m. there were around three times as many birds of both species
compared to 9 a.m. The increases are probably because the students eat lunch outdoors at 12 noon, and
may snack as they leave school at 3 p.m. Therefore, there would be crumbs (bread scraps) for the birds to
eat at 1 p.m. and 3 p.m. and the birds would be attracted to eat these leftovers.
Activity 8
a) For example: leaves → caterpillar → common bulbul → black kite
b) For example: If the rove beetles and ants disappeared, there would be fewer insects for birds such as
the common bulbul and starling. These birds would have to find alternative sources of food.
c) Advice for ensuring the evidence is reliable could include: keeping data on a school computer so it can
be added to regularly; getting the whole school involved so that more students collect observations,
which will make the database larger; collecting the data and storing it from one year to another to
allow comparisons; making a note of any events/changes (e.g. droughts, floods, extreme temperatures,
lunchtimes moved inside, changes in school timings), to see if they have an effect on the data.
Activity 10
Box 1
Ordovician, 445–430 million years ago, ice age / glaciers / volcanic activity, 85% extinct
Box 2
Late Devonian, 376–360 million years ago, sea level rise/fall / less O2 and CO2, 75% extinct
Box 3 Permian/Triassic, 252 million years ago, volcano / asteroid / dust, 95% marine invertebrates and
70% land invertebrates extinct
Box 4
Jurassic–Jurassic, 201 million years ago, climate change / volcanoes / asteroid, 76% extinct
Box 5
Cretaceous–Tertiary, 66 million years ago, asteroid, 75% species extinct
Activity 11
Some scientists believe Earth is heading for another mass extinction event because of, for example: global
warming, sea levels rising, pollution, human activity leading to climate change, etc.
Activity 12
a) Pinta giant tortoise – extinct because they were hunted for food.
West African black rhinoceros – extinct due to poachers killing them for their horns (which were sold on
the black market and used in traditional medicine).
Golden toad – extinct due to human activity, such as deforestation and climate change caused by
people burning fossil fuels.
Paradise parrot – extinct due to drought, people burning local grass each year and grazing cattle on the
grass, all of which severely reduced the parrots’ food supply because they ate the grass seed.
Guam flying fox – extinct because humans introduced new predators such as the brown tree snake in
their habitat, hunted the flying foxes, and destroyed their habitat through deforestation.
Hawai’i ‘o’o – extinct because humans destroyed their habitat and introduced rats, which ate the birds’
eggs.
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b) The common cause is human activity, such as poaching, hunting, causing climate change, introducing
new predators to their habitats, and changing habitats through farming and deforestation.
Revision test answers
1
C
2
A and C
3
true; false; true; true; true
4
For example:
a) The Great Dying was a mass extinction event where over 75% of plants and animals on Earth
became extinct.
b) The Red List is the International Union for Conservation of Nature’s (IUCN) list of animals and plants
threatened with extinction.
c) An extinction event is when animals and plants become extinct in large numbers very quickly.
5
For example: Most of the animals on Earth became extinct / There was a major event, e.g. an asteroid
hit the Earth, global temperature change, volcanic eruption.
6
For example: Taking and recording observations over long periods of time is important because it
enables scientists to see trends and patterns in data and gives more reliable data.
7
For example: As the number of hares increases or decreases, the number of lynxes follows the same
pattern, suggesting the hare is the prey of the lynx.
8
For example: In 1855, the numbers of both lynxes and hares were fairly high. This suggests that the lynx
population was healthy because the hare population was high and provided food. Then, the hare
population started to fall, perhaps because there were so many lynx to eat them. By around 1862,
levels of both were very low, showing the link between predator numbers and lack of prey – when the
hare numbers are low, the lynx food source is scarce and so lynx numbers decrease.
9
In most years, as the hare population rises and falls, the lynx population does the same. The two
populations directly affect each other, since the lynxes prey on the hares.
10 Any three from: hunting for food; pollution; hunting to destroy a species or for sport; changes in land
use such as deforestation for agriculture; climate change; etc.
11 Reasons why scientists disagree could include: the events were millions of years ago; no one was there
to witness what happened so we can only use the evidence left behind; the evidence can be
interpreted in different ways.
12 The Anthropocene Epoch is the period of time that we live in now. Animal and plant species could go
extinct due to the effect of humans on the environments, plants and animals on Earth – for example,
due to use of fossil fuels, pollution, deforestation, agriculture and industry causing climate change
through a dramatic rise in carbon dioxide in the air, etc.
Cambridge Checkpoint Science Revision Guide for the Cambridge Secondary 1 Test
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Cambridge Checkpoint Science Revision Guide Second
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Chapter 6 answers
Activity 3
a) hydrogen, H, 1, gas, non‐metal
carbon, C, 6, solid, non‐metal
iron, Fe, 26, solid, metal
gold, Au, 79, solid, metal
mercury, Hg, 80, liquid, metal
b) Similarity: For example, both are made up of neutrons, protons and electrons.
Difference: For example, a carbon atom has more neutrons (six), protons (six) and electrons (six) than a
helium atom (two of each).
Activity 4
Timeline order, boxes from left to right: B, E, C, D, F, A
Activity 6
a) The melting points of the elements decrease as you go down the group.
b) The boiling points of the elements increase as you go down the group.
c) Mono means single or one, so monatomic means that these gases are made up of single atoms, rather
than molecules in which more than one atom is joined together.
d) Ductile means it can be drawn out into a wire without breaking. This is useful for making jewellery,
cables and wires. Malleable means it can be hammered or rolled into thin sheets. This is useful for
making foils, jewellery and kitchen utensils.
e) For example:
Alkali metals
Name
Uses
Noble gases
Name
Uses
lithium
medication and batteries
helium
filling balloons, helping people
breathe in hospitals (mixed with
oxygen)
sodium
seasoning food (sodium chloride –
salt), cleaning products
neon
lights, fog lights, lasers
caesium
solar cells, atomic clocks
radon
in radioactive research
Revision test answers
1
C
2
B
3
C
4
false; true; false; true
5
Any three from: electrical conductors, malleable, ductile, react easily with water
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6
Any three from: non‐flammable, tasteless, odourless, colourless, inert/non‐reactive, poor conductors of
electricity
7
A monoatomic gas means each gas particle has only one atom.
8
Answer A: 2 marks because it has described the properties of malleable and ductile materials but does
not give examples of either or say whether a material can have both properties.
Answer B: 5 marks because it has described the properties of malleable and ductile materials, given
examples of malleable and ductile materials, and stated that some materials can be both malleable and
ductile.
9
The mistakes are:
1
It says periods are vertical rows but they are actually horizontal rows.
2
It says groups are horizontal rows but they are actually vertical columns.
3
It says noble gases are on the left of the periodic table but they are actually on the right‐hand side.
4
It says alkali metals are on the right but they are on the left‐hand side of the periodic table.
5
It says elements are impure substances but they are pure substances.
Chapter 7 answers
Activity 2
Moyo’s model is incorrect. She has labelled protons in orbits and has neutrons as a cloud around the
nucleus. (She has also missed out electrons.)
Activity 3
oxygen – unstable
neon – stable
beryllium – unstable
Activity 4
Oxygen has a double bond, so a second strand of spaghetti needs to be added between the two
marshmallows. This represents a second covalent bond (a second pair of shared electrons).
Activity 5
a)
Molecule
name
Structure of
molecule
hydrogen
oxygen
methane
H–H
O=O
H
(Note the
double
bond)
|
water
chlorine
Cl–Cl
H–C–H
|
H
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b) Learners are likely to agree, because this model does not show the number of bonds between the
atoms.
Activity 6
oxygen – negative ion, anion
neon – no change, ‘not an ion’
magnesium – positive ion, cation
Activity 7
A – yes; B – yes; C – no
Activity 8
Giant covalent structure
Definition – large molecular structure of atoms held together by strong covalent bonds
Characteristics/features/facts – high melting and boiling points due to strong covalent bonds
Example – diamond, which has a regular tetrahedral shape
Non‐example – magnesium oxide
Giant ionic structure
Definition – large structure of ions held together by forces between opposite electrical charges
Characteristics/features/facts – insulators when solid, conductors when dissolved or molten, high melting
and boiling points due to strong attraction between ions in the structure
Example – sodium chloride, which has a regular cubic shape
Non‐example – graphite
Activity 9
Simple molecules
Giant covalent structures
Giant ionic structures
A E
B
C
D
F
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Revision test answers
1
2
false; true; false
3
false; true; true
4
false; true; false
5
C
6
C
7
red – oxygen; white – hydrogen; blue – nitrogen; green – fluorine/chlorine; black – carbon
8
Simple molecules have strong forces between the atoms in the molecule, which hold the molecule
together. However, they only have weak forces between the molecules. These forces only hold the
molecules together when it is cold and are easily broken at higher temperatures (by the increased
kinetic energy of hotter moving particles). Giant covalent molecules have strong covalent bonds
between all the atoms within the single large molecule. These bonds are require a lot of energy to
break, so the substances have very high melting and boiling points.
9
In the solid salt, the positive sodium ions and the negative chloride ions are arranged in a giant ionic
structure or lattice. The ions are charged but are attracted to one another and so cannot move around,
so solid sodium chloride cannot conduct electricity.
10 a) magnesium: positive; chlorine: negative
b) Magnesium loses two electrons; Chlorine gains one electron.
c) MgCl2 (For every one magnesium atom, there are two chlorine atoms.)
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Chapter 8 answers
Activity 3
Block
Density
small
medium
large
density =
density =
density =
=
=
=
.
.
= 20 kg/m3
.
= 20 kg/m3
= 20 kg/m3
Theo is correct. The density is the same for each block because it is the same material (and density is a
property of the material, which is not affected by the size of the block).
Activity 4
Substance
Density
ice
steel
air
density =
density =
density =
=
=
=
= 917 kg/m3
= 8000 kg/m3
.
= 1.27 kg/m3
Activity 5
1
a) 50 kg = 50 000 g
b) 370 kg = 370 000 g
c) 419 kg = 419 000 g
2
a) 50 000 g = 50 kg
b) 2500 g = 2.5 kg
c) 100 g = 0.1 kg
3
a) 5 cm = 0.05 m
b) 350 mm = 0.35 m
c) 1000 cm = 10 m
d) 20 m = 2000 cm
Activity 6
Wax – The units should be g/cm3 (or the number should be 950 if in kg/m3).
Aluminium – The answer would be correct if in kg/cm3. More common units would be kg/m3 (density =
2700 kg/m3) or g/cm3 (density = 2.7 g/cm3).
Stone – The answer would be correct if in g/mm3. More common units would be g/cm3 (density = 3 g/cm3)
or kg/m3 (density = 3000 kg/m3).
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Activity 7
We started by getting (measuring) the mass (not weight) of the block using a top‐pan balance.
We found the volume of the block by measuring the depth, width and length using a ruler (three
measurements, not two).
We calculated the volume of the block by multiplying the depth, width and length together (three
measurements multiplied together, not two).
Activity 8
Volume of liquid at start
Volume of liquid + object
Volume of object
50 cm3
60 cm3
10 cm3
20 cm3
47 cm3
27 cm3
72.5 cm3
85 cm3
12.5 cm3
Activity 9
Vinegar is the more dense liquid. The oil is floating on top of the vinegar, so it must be less dense.
Activity 10
They have forgotten to subtract the mass of the empty container and have included this in their calculation
of the density. Their calculations and method are otherwise correct, so if they find the mass of the empty
container (evacuated using a vacuum), they will be able to find the mass of just the gas.
They also did not check the volume of the flask (they relied on the volume printed on the flask). The actual
volume of gas might be different (although this would have a much smaller effect on the accuracy of the
results).
Activity 11
Correct order: A, D, C, E, B, F.
Revision test answers
1
C
2
B
3
A
4
C
5
volume = 8 cm × 9 cm × 2.2 cm = 158.4 cm3
density =
6
=
= 1.073 g/cm3 (or 1073 kg/m3)
.
volume of stone = 90 cm3 – 40 cm3 = 50 cm3
density of stone =
=
= = 1.6 g/cm3
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7
mass of honey = 235 g – 33 g = 202 g
density =
8
=
= 1.40 g/cm3
Measure the mass of the empty container (emptied by using a vacuum).
Subtract the mass of the empty container from the mass of the container and gas.
Check the volume of the flask by filling it with liquid and measuring the volume of the liquid.
9
The density of the steel bolt is > 1430 kg/m3, as it is more dense than sugar syrup. Any answer greater
than 1430 kg/m3 is acceptable.
The density of the sultana is > 1000 kg/m3 but < 1430 kg/m3, as it is more dense than water but less
dense than sugar syrup. Any answer between 1000 kg/m3 and 1430 kg/m3 is acceptable.
The density of the tomato is > 920 kg/m3 but < 1000 kg/m3, as it is more dense than oil but less dense
than water. Any answer between 920 kg/m3 and 1000 kg/m3 is acceptable.
Chapter 9 answers
Activity 1
The more reactive metals in each pair are:
a) calcium
b) iron
c) magnesium
d) magnesium
e) aluminium
Activity 4
magnesium + copper chloride: yes – bubbles released, temperature changes, colours change
iron + zinc nitrate: no – no changes observed
zinc + lead nitrate: yes – change of colour of metal
Activity 5
a) Bubbles of hydrogen gas are formed (slowly) and/or indicator phenolphthalein changes colour to
indicate the presence of the alkali magnesium hydroxide.
b) magnesium + water → magnesium hydroxide + hydrogen (in either order)
Activity 7
a) Iron – Yes, iron is higher in the reactivity series than hydrogen.
b) Copper – No, copper is lower in the reactivity series than hydrogen.
c) Magnesium – Yes, magnesium is higher in the reactivity series than hydrogen.
d) Zinc – Yes, zinc is higher in the reactivity series than hydrogen.
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Activity 8
Any one of the following:
iron + hydrochloric acid → iron chloride + hydrogen
magnesium + hydrochloric acid → magnesium chloride + hydrogen
zinc + hydrochloric acid → zinc chloride + hydrogen
Activity 9
a) aluminium + iron oxide → aluminium oxide + iron
b) Replacing aluminium with lead would not allow the thermit reaction to take place, because lead is
lower in the reactivity series than iron, so it is less reactive than iron. Displacement reactions only take
place when a more reactive metal is able to replace a less reactive metal.
Activity 10
a) 1
Iron key – yes: iron + copper sulfate → iron sulfate + copper
2
Silver spoon – no reaction
3
Gold ring – no reaction
4
Zinc name badge – yes: zinc + copper sulfate → zinc sulfate + copper
b) No, it is incorrect. Only metals that are reactive enough will displace the copper. The others will not
change no matter how long they are left in the solution of copper sulfate.
c) If the metal that the object is made from is more reactive than copper, displacement will take place and
copper will form. If the metal that the object is made from is less reactive than copper, there will be no
displacement reaction and no coating will form.
Revision test answers
1
no; yes; yes; yes
2
true; false; false; false
3
B and D
4
B and D
5
a) calcium + zinc sulfate → calcium sulfate + zinc
b) lead + iron chloride → no reaction
c) zinc + hydrochloric acid → zinc chloride + hydrogen
d) copper + nitric acid → no reaction
6
Method:



Place (equal amounts of) an acid (e.g. sulfuric, hydrochloric or nitric acid) into different test tubes.
Place (equal sized) pieces of each of the metals (that can be safely handled, i.e. below calcium) from
the reactivity series, one into each tube, including tin.
Use a stopwatch to measure a fixed amount of time, e.g. 5 minutes.
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


Either count the bubbles from the reaction of each metal with the acid in the time, or collect the
gas using a bung to seal the tube, a delivery tube into a water bath and an upturned measuring
cylinder with water that will be displaced as the gas fills the test tube.
Observation – look for formation of bubbles of (hydrogen) gas or a colour change.
Decide if more or less reactive – look at the number of bubbles/amount of gas formed in a
particular time (more bubbles = faster reaction) across each of the metals. When comparing the
metals, the ones with the most bubbles/amount of gas in a given time will be the most reactive.
Chapter 10 answers
Activity 2
Metals
Acids
Salts
zinc
sulfuric (acid)
magnesium chloride
calcium
nitric (acid)
iron sulfate
copper
hydrochloric (acid)
lead nitrate
Activity 3
a) chloride
b) sulfate
c) nitrate
Activity 4
Metal
Acid
Salt
magnesium
nitric acid
magnesium nitrate
calcium
hydrochloric acid
calcium chloride
zinc
sulfuric acid
zinc sulfate
Activity 6
Aga’s is the best statement. Ahmed’s statement is not true – it is a type of purification, because the
substance is a mixture at the start and separate compounds at the end. Emilia’s statement is not true
either, as the bubbles in this case are a sign of the water boiling (turning from liquid to gas), which is a
reversible physical change rather than a chemical reaction.
Activity 7
The correct order is: B, C, E, D, A.
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Activity 8
a) zinc + sulfuric acid → zinc sulfate + hydrogen
b) The correct order is: B, E, C, D, A.
c) The two mistakes are:


Statement C mentions magnesium but it should be zinc as they are making a zinc salt.
Statement B mentions nitric acid but it should be sulfuric acid as they are making a sulfate.
Activity 9
magnesium carbonate + hydrochloric acid → magnesium chloride + water + carbon dioxide
Question
Daanesh’s response Is he correct? Correct answer (if needed)
What is the name
of the acid
used?
nitric acid
no
hydrochloric acid
What would be left
in the filter
funnel?
excess unreacted
magnesium
carbonate
yes
How would you
separate the
magnesium
chloride from
the solution?
filtration
no
Use evaporation to remove the
water from the solution, leaving
crystals of magnesium chloride.
A gas is produced.
What do you
think it is and
how would you
test for it?
hydrogen gas, tested no
for by collecting,
inserting a lit
splint and getting
a ‘squeaky pop’
carbon dioxide, tested for by seeing
if it makes limewater turn
cloudy
Activity 10
Separating copper powder from
zinc sulfate solution
Filtration
Obtaining solid iron chloride from
an incomplete reaction of
copper chloride and iron
(filings)
Filtration, evaporation and
crystallisation
Separating soluble magnesium
chloride from a solution
Evaporation and crystallisation
Revision test answers
1
true; false; true; true
2
true; true; false; false
3
B
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4
A
5
a) magnesium + nitric acid → magnesium nitrate + hydrogen
b) lead + sulfuric acid → lead sulfate + hydrogen
c) calcium carbonate + nitric acid → calcium nitrate + water + carbon dioxide
d) magnesium carbonate + hydrochloric acid → magnesium chloride + water + carbon dioxide
6
a) copper carbonate + nitric acid
b) Method:






Add (excess) copper carbonate to a flask.
Add nitric acid.
Wait until bubbles have stopped.
Filter out excess copper carbonate (using filter funnel and beaker).
Heat to evaporate the water from copper nitrate solution until almost dry.
Leave to crystallise (pat dry the crystals).
c) copper carbonate + nitric acid → copper nitrate + water + carbon dioxide
d) 1
2
Replace copper carbonate with calcium carbonate.
Replace nitric acid with hydrochloric acid.
Chapter 11 answers
Activity 2
Fastest B (typically takes seconds), D (typically takes a few minutes), A (typically takes many minutes, up to
an hour), C (typically takes weeks, months or years) Slowest
Activity 3
a) copper + oxygen → copper oxide
b) 2.5 g (The total mass of products must equal the total mass of reactants: 12.5 g.)
c) 5 g: double the mass of copper will require double the mass of oxygen
d) 25 g: double the mass of copper oxide is also produced (or 20 g + 5 g = 25 g)
Activity 4
a) Non‐closed system as air can get in
b) magnesium + oxygen → magnesium oxide
c) Bella is correct.
Activity 5
Suki – the total amount of energy afterwards equals the total amount beforehand. Emma’s answer shows
more energy afterwards so breaks the conservation of energy law.
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Activity 6
a) acid + metal carbonate → metal salt + water + carbon dioxide (any order)
b) 157.5 g – 155.8 g = 1.7 g
c) non‐closed
d) Production of bubbles of (carbon dioxide) gas
e) hydrochloric acid + calcium carbonate → calcium chloride + water + carbon dioxide
f) HCl + CaCO3 → CaCl2 + H2O + CO2 (unbalanced)
2HCl + CaCO3 → CaCl2 + H2O + CO2 (balanced)
Activity 7
a) acid + metal → metal salt + hydrogen
b) closed
c) Bubbles of (hydrogen) gas released at the site of the reaction
d) magnesium + hydrochloric acid → magnesium chloride + hydrogen
e) Mg + HCl → MgCl2 + H2 (unbalanced)
Mg + 2HCl → MgCl2 + H2 (balanced)
Activity 8
a) carbon dioxide
b)
Activity 9
The large combined surface area of the custard powder dust would make a combustion reaction happen
very quickly indeed and so could produce a dangerous explosion.
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Activity 10
a)
Particle
size
Mass of container at
start of experiment/g
Mass of container at
end of experiment/g
Mass lost during
experiment/g
small
185.5
181.4
4.1
medium
185.5
182.7
2.8
large
185.5
183.9
1.6
b) The larger the particle size, the lower the amount of mass lost (or the smaller the particle size, the
greater the amount of mass lost).
c) The larger the particle size, the lower the rate of reaction (or the smaller the particle size, the higher
the rate of reaction).
Activity 11
Temperature of acid (°C)
Time taken to fill the container (s)
20
123
30
89
40
63
50
45
60
32
Activity 12
a) Catalysts can be installed in cars in catalytic converters. These speed up the rate at which harmful gases
like carbon monoxide are converted into less toxic substances like carbon dioxide and water, reducing
pollution.
b) Enzymes and metals like platinum, rhodium and iron
Activity 13
a) oxygen
b) heat
c) oxygen
d) heat
e) fuel
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Activity 14
Revision test answers
1
false; true; true; true
2
B
3
D
4
a) CH4 + O2 → CO2 + H2O (or balanced: CH4 + 2O2 → CO2 + 2H2O)
b) HCl + CaCO3 → CaCl2 + H2O + CO2 (or balanced: 2HCl + CaCO3 → CaCl2 + H2O + CO2)
c) HCl + Mg → MgCl2 + H2 (or balanced: 2HCl + Mg → MgCl2 + H2)
5
6
Reactant 1
Reactant 2
Product 1
Product 2
36.5 g of
hydrochloric
acid
12 g of
magnesium
46.5 g of
magnesium
chloride
2 g of hydrogen
9.8 g of sulfuric
acid
10 g of calcium
carbonate
13.6 g of calcium
sulfate
1.8 g of water
Product 3 (if
applicable)
4.4 g of carbon
dioxide
a) zinc + sulfuric acid → zinc sulfate + hydrogen
b) Measure the mass of the reaction vessel before the experiment (using a balance). Measure the loss
of mass from the reaction in a certain time. Use this to calculate the rate of reaction.
7
a) magnesium carbonate + nitric acid → magnesium nitrate + water + carbon dioxide
b) Collect the gas in a gas syringe. Measure the amount of gas produced in a certain time. Use this to
calculate the rate of reaction.
8
As the concentration of sulfuric acid increases, the rate of reaction also increases. Increased
concentration means an increased number of acid particles in the solution. This increases the chances
of collisions (and reactions) with magnesium particles.
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9
The larger the pieces of calcium carbonate, the smaller the total surface area. This reduces the rate of
reaction. Reactions take place at the surface of the pieces: the smaller the surface area, the fewer
reactant particles can come into contact to react.
10 The higher the temperature, the faster the particles (of acid) are moving. This increases the rate of
reaction. The faster‐moving particles are more likely to collide (with the sodium thiosulfate particles).
They are also likely to hit the particles harder, increasing the chances of a reaction.
Chapter 12 Answers
Activity 2
a) water:
13 102 + 13 006 + 13 207 = 39 315
vegetable oil:
5551 + 5335 + 5422 = 16 308
soil (wet): 8131 + 8059 + 8032 = 24 222
sand:
2919 + 3022 + 2858 = 8799
39 315  3 = 13 105
16308  3 = 5436
24 222  3 = 8074
8799  3 = 2933
b) water
c) sand
d) water
e) sand
f) Higher, because more energy would have to be transferred to the substances
Activity 3
a) no – move around more
b) yes
c) yes
d) no – it measures the average energy of the particles (the temperature).
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Activity 4
Example of energy
transfer
Energy store at start –
amount and type of store
Energy store at end (1) –
amount and type of store
Energy store at end
(2) – amount and
type of store
Chemical store in the
battery
Transferred as light,
ending up in a thermal
store when light is
absorbed
Transferred to
surroundings,
ending up in a
thermal store
Thermal store in the
kettle
Transferred to
surroundings, ending
up in a thermal store
Switching on a torch
A kettle cooling down
to room
temperature
An exothermic
chemical reaction
(e.g. lighting a
match)
Chemical store in the
match
Transferred to
surroundings, ending
up in a thermal store
Transferred as light to
surroundings,
ending up in a
thermal store
Activity 5
Inside the liquid: Convection
Warmer particles are more spread out and so less dense. The warmer particles rise and carry energy
upwards.
From the top surface of the liquid: Evaporation
Particles move away from the surface of the liquid, taking thermal energy with them.
Through the bottom of the cup: Conduction
Particles vibrate due to their kinetic energy and pass these vibrations on to the particles next to them.
(Note: A china cup is an insulator, so this will not happen very quickly.)
From the side surface of the cup: Radiation
Infrared radiation (waves) is emitted from the side of the cup, passing the energy to the surroundings.
Activity 8
Answer A: full marks (5 marks); all points scored.
Answer B: 1 mark scored for identifying water is not a good conductor; no other points scored.
Answer C: 2 marks; scored for identifying radiation and stating that energy moves from a warm object to
the surroundings. Incorrect description of radiation as particles rather than waves prevents further
points being scored.
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Revision test answers
1
C
2
D
3
Thermal energy is the total amount of kinetic (movement) energy of all of the particles in an object.
Temperature is the average amount of kinetic (movement) energy of the particles in a substance.
Compared with a glowing metal light filament, a bath of warm water has the larger amount of thermal
energy.
Compared with a bath of warm water, a glowing metal light filament has the higher temperature.
4
Conduction happens through solid substances, particularly metals.
Convection explains why warm air rises.
Radiation can be detected through infrared imaging.
Evaporation occurs when particles leave a surface and take the thermal energy with them, cooling the
surface down.
5
Possible examples include:



seeing warm objects at night
finding people/objects hidden by smoke in a fire
diagnosing disorders in the body without touching them.
The warmer parts of the objects give out more infrared radiation than the cooler parts.
6
Evaporation – particles of water in the sweat are heated by the warm skin. They then have enough
energy to leave the surface (evaporate). They take the energy that they are carrying with them, away
from the skin and into the surroundings. This cools the skin down.
7
Energy cannot be created or destroyed. It simply transfers from one place/object to another.
Answer can include any example that shows that the amount of energy within an isolated system does
not change. For example, with a pan being heated, the total amount of energy supplied to the pan ends
up heating the pan, its contents and the surroundings.
8
Metals have electrons that are free to move (sometimes described as a ‘sea’ of electrons). When a
metal is heated, the electrons in that part move about more quickly and pass on thermal energy to
nearby electrons and atoms, so the heat spreads quickly through to the cool part of the metal.
9
A thermal insulator is a poor conductor of thermal energy. Most substances that are not metals are
insulators, such as wood, plastics, fabrics, etc.
Chapter 13 answers
Activity 2
The correct order is: (A), E, B, C, D, (F).
Activity 3
Cho’s statement is correct. Sounds are quieter when you are further away from the source of the sound (as
the sound spreads out).
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Activity 4
a) vibrating object
b), c)
compression / high pressure (these labels can be either way around)
d), e)
rarefaction / low pressure (these labels can be either way around)
f) direction of travel of sound
Activity 5
Medium
Gas, such as air
Solid, such as
glass
A vacuum, such
as outer
space
Liquid, such as
seawater
Speed of sound
330 m/s
2840 m/s
no sound
1560 m/s
Activity 6
a) louder sound
b) quieter sound
c) higher pitched sound
Activity 7
As the police car approaches, the pitch is higher than normal.
As the police car is nearest them, the sound is a normal pitch.
As the police car is travels away, the pitch is lower than normal.
Activity 8
Loud sound
A large stone
Quiet sound
A small stone
A high frequency
A few stones, thrown in quickly one after the other
A low frequency
A few stones, thrown in slowly one after the other
Activity 9
The noise can be cancelled out if the opposite waves are played at the same time as the sound. If that
happens, you will get destructive interference.
Revision test answers
1
true; false; true; false; true
2
C
3
A
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4
5
compressions
high pressure
rarefactions
low pressure
high amplitude
loud sound
low frequency
low pitch
A
amplitude
B wavelength
C
amplitude
D wavelength
6
Key points you might include are:




7
vibrations caused by moving object
hit particles within the air
causing compressions and rarefactions
travel as sound waves (to the ear)
a) For example: Waveform A has a lower amplitude than waveform B, so A is quieter than B (or B is
louder than A). The waveforms have the same wavelength (same frequency) so they will have the same
pitch.
b) For example: Waveform A has a lower frequency (or a longer wavelength) than B, so A is lower
pitched than B (or B is higher pitched than A). The waveforms have the same amplitude, so have the
same loudness.
8
For example: The source of the sound is moving (compared to the listener). This changes the pitch of
the sound. As the object approaches, the pitch is higher than it would normally be. As the object moves
away, the pitch is lower than normal. (The faster the source is moving, the larger the change in pitch.)
9
For example:



To model a sound wave, the motion should be back and forth (not side to side).
Changing how often they move their hand will change the frequency (not amplitude).
Changing how far they move their hand will change the amplitude (not frequency).
Chapter 14 answers
Activity 3
Circuit A: The lamp will not produce any light, as the only lamp in the circuit is broken.
Circuit B: Neither lamp will light, as one of the lamps is broken so the series circuit is incomplete.
Circuit C: The bottom lamp will light, as the loop it is in forms a complete circuit. The broken lamp in the
first loop will not light.
Activity 4
a) A and C are correct
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b)
Ammeter
Current/amps
A1
1.0
A2
0.5
A3
0.5
A4
1.0
c) No matter where you place the ammeter in a loop, the current reading is the same. This is because the
current is the same at all points in a loop.
Activity 5
B and C are correct.
Activity 6
a) The middle cell is in the opposite direction to the other cells.
b) There are two cells in one direction, and one in the other. This means that the battery produces a
smaller voltage, equivalent to one cell (rather than three).
c) 1.5 V
d) Cells in one direction = 3.0 V; cells in the other direction = 1.5 V; 3.0 V − 1.5 V = 1.5 V
Activity 7
For example: Current is the rate of flow of charge (or how much charge flows in a given time) around a
continuous circuit (or loop). Voltage is the ‘push’ given by the cell or battery and is the energy ‘carried’ by
each unit of charge.
Activity 8
a) The brightness of the lamps does not change.
b) If one of the lamps breaks, the other lamps will stay lit.
Activity 9
a) Yes, it is correct.
b) No, they have connected the ammeter and voltmeter in the wrong places so the readings are not
correct.
Activity 10
Circuit A: fixed
Circuit B: variable
Circuit C: variable
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Revision test answers
1
A
2
A
3
B
4
false; true; false; false; true
5
6
lamp
Glows when current passes through
ammeter
Used to measure the current in a circuit
current
The flow of charges around an electric circuit
voltmeter
Always placed in parallel with a component
ampere
The unit of electric current
a)
b) The lamp will light and the buzzer will sound.
c) i)
2.8 V
ii)
2.8 V
d) i)
stays the same
ii)
decreases
iii)
decreases
e) The voltage (push) of the battery does not change, but no electricity flows around the circuit as the
switch is open. This means there is no voltage across the other components.
7
a) lower
b) series
c) parallel
d) the same
e) divided
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8
a) The circuit in the top loop is incomplete, as lamp A is in series with lamp B. No current can flow
around this loop, so no electrical energy is transferred to lamps A and B and they do not light up.
Lamp C stays lit, as it is in parallel with lamp B and its circuit remains complete. A current can flow
and electrical energy can be transferred to lamp C.
b)
Ammeter
Current/A
A1
0.75
A2
0.5
c) The current is halved as the resistance is twice as much.
Chapter 15 answers
Activity 2
a) 1D; 2F; 3A; 4B; 5C; 6E
b) 1, 2, 4 – Jigsaw appearance of coasts and distribution of some fossils and rocks indicates that all of the
land mass was together at one time.
c) 3, 5, 6 – Mountains continue to form and grow, earthquakes and volcanoes occur along plate edges,
polarity of magnetic stripes changes and magnetic stripes are moving apart over time.
Activity 4
a) 1 – mantle; 2 – inner core; 3 – crust; 4 – outer core
Activity 5
a) both
b) S waves
c) both
d) S waves
e) both
f) S waves
g) both
h) P waves
i) P waves
j) P waves
Activity 6
a) (best) B; A; C (worst)
b) Answer B has correct science and lots of detail to explain the ideas. Answer A has correct science but
fewer details. Answer C has incorrect science.
Revision test answers
1
Maps of the Earth’s landmass; mapping of rock distribution; mapping of earthquakes; mapping of
volcanoes
2
A and B
3
false; false; true; false; false
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4
5
P waves
Seismic waves that can travel through solids
and the liquid outer core
S waves
Seismic waves that cannot travel through the
liquid outer core
Seismic waves
The two types of waves produced in an
earthquake that travel down into the Earth
Seismometer
Measuring instrument used to analyse seismic
waves produced in an earthquake
Example answers:
a) Magma – liquid/molten rock below the Earth’s surface
b) Tectonic plate – massive, irregularly-shaped slab of solid rock floating on top of magma
c) Seismic wave – a wave that shifts energy in the Earth produced by an earthquake (or other means)
6
a) P wave b)
S wave c)
d) both
P wave
e)
both
7
false; true; false; false; false
8
left‐hand image = P waves; right‐hand image = S waves
9
10 Any five of the following points:





The hottest part of the Earth’s structure is the inner core.
The inner core heats up the outer core, which in turn heats up the mantle.
The mantle is made up of magma (molten rock), so the energy is transferred through it by
convection.
Convection occurs when thermal energy is transferred through a liquid or a gas by the movement of
particles in the substance.
The magma closest to the outer core heats up first.
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


The particles in this magma move more quickly / gain more kinetic energy, and spread apart,
becoming less dense than the magma above.
This less dense magma then rises and cooler magma replaces it.
The convection currents rise to underneath the Earth’s crust and move along under the tectonic
plates. This moves the plates.
Chapter 16 answers
Activity 3
a) feeding
b) decomposition
c) respiration
Activity 4
This is the complete correct text:
Carbon dioxide is classified as a ‘greenhouse gas’ because it allows heat energy from the Sun to travel
through and reach the surface of Earth, but then prevents much of the heat energy radiating from the
Earth’s surface from passing back out into space, because the carbon dioxide absorbs the energy and
warms up the atmosphere, like a greenhouse. This process is known as global warming.
Over two hundred years ago, the Industrial Revolution occurred in several countries and factories were
built, which used coal, oil and gas to power machines using a combustion reaction. This released more
carbon dioxide into the atmosphere.
Scientists have measured global temperatures since 1880 and the patterns show that the temperature is
rising. As well as monitoring temperatures, scientists have measured changes over time in precipitation,
humidity, wind speed and atmospheric pressure. These changes are known as climate change and are
linked to rises in carbon dioxide levels.
Activity 5
a) 1940s
b) 800 000 years
c) Zero
d) About 410 parts per million; this is the current level
e) Just below 1 °C, in 2016 and 2017
f) Since the 1970s/1980s; from this point, the gradient of the graph shows a steep increase
g) Since the 1950s; the graph is very steep and increasing rapidly over a very short time period
h) For example: Yes, because both are now going up very quickly.
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Activity 6
Example answers:
a) Rising sea levels: flooding of low‐lying islands and coastal areas; people moving away from these areas
Changing humidity levels: more water in atmosphere; changing weather patterns; very heavy rain; flash
floods; droughts; destruction of property / habitats / crops / livestock
Extreme weather events: larger and more frequent extreme weather events, such as hurricanes,
tornadoes and heavy snowstorms; leading to floods, damage to environments and property and
increased risk to life
b) End reliance on fossil fuels; find and use alternative fuels; invest in clean and renewable energy sources;
use sustainable transport; keep homes well insulated; encourage people to reduce the amount of meat
they eat or even switch to vegan diets; plant trees; protect forests and oceans; reduce consumption of
goods; use less plastic
Revision test answers
1
photosynthesis; respiration; feeding
2
photosynthesis
3
true; false; false; true; true; false
4
greenhouse gas
Any gas in the atmosphere that absorbs some thermal energy from
the Sun, with the result that the atmosphere becomes warmer
carbon dioxide
A colourless, odourless gas consisting of a carbon atom covalently
double‐bonded to two oxygen atoms
global warming
Increase in average temperature of the Earth, which is likely to lead
to significant climate changes
climate change
Long‐term shifts in temperatures and weather patterns
5
Rapid increases in global temperature; rapid increases in level of carbon dioxide
6
For example: increasing sea levels; increasing humidity; more frequent extreme weather events
7
a) both
b)
respiration
c)
combustion
d) both
e)
combustion
f)
both
g) respiration
8
For example: As the Earth heats up, ice (e.g. at the poles, in glaciers and on mountains) is melting,
causing sea levels to rise. This leads to flooding of low‐lying areas. Some islands have been or will be
lost, and people will have to move away from coastal areas to live, etc.
9
For example: keep fossil fuels in the ground; find alternative fuels; invest in clean and renewable energy
sources; use sustainable transport and move items over shorter distances to reduce the use of fuel;
keep homes warm by using insulation as much as possible; encourage people to eat less meat or even
switch to vegan diets; plant more trees, which generate oxygen from carbon dioxide; protect forests
and oceans, which capture carbon and reduce the amount of carbon dioxide in the atmosphere; reduce
consumption of goods, so fewer items need to be manufactured, using less energy, etc.
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Chapter 17 answers
Activity 2
a) Width and depth of craters
b) The height from which the rock is dropped
c) Same rock; same person dropping rock; same method of release to drop rock; same measuring
instruments used; same person using the measuring instruments; sand smoothed over before each
drop
d) The likely width of the crater is 16 mm, because the values tend to go up by 2 mm for every 10 cm
increase in drop height. The likely depth of the crater is 7 or 8 mm, because the values tend to go up by
1 mm for every 10 cm increase in drop height.
e) As the height from which the rock is dropped increases, and therefore the speed at which the rock hits
the sand increases, the depth and width of the crater created also increases.
f) They could have repeated each drop and calculated average values.
Activity 3
a) For example: craters; climate change; mass extinctions
b) Dust and ash are sent into the atmosphere and can block the Sun’s heat and light.
c) Dust, ash, water vapour and droplets are sent into the atmosphere and can block the Sun’s heat and
light.
d) When large numbers of species become extinct at the same time.
Activity 4
a) Evidence from rocks: 3, 6
b) Evidence from movement: 1, 4
c) Evidence from observations: 2, 5
Activity 5
Example answer:
Stellar nebula: A stellar nebula can form from clouds of hydrogen gas in the universe. Gravity pulls the
hydrogen atoms together into a huge ball, called a protostar.
Protostar: Gravity continues to squash the gas atoms in the protostar closer and closer together. This
increases the pressure and the temperature inside the ball. Eventually, the pressure on the hydrogen atoms
is so great that they fuse together to make helium gas. This releases energy as heat and light, and the ball
begins to glow.
Main sequence star: As the pressure and temperature continue to increase inside the glowing ball, more
hydrogen is converted into helium. The ball starts to shine and a main sequence star is ‘born’.
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Revision test answers
1
between Mars and Jupiter; in the same orbit as Jupiter
2
A and B
3
false; false; true; false; true; false
4
5
Moon
The Earth’s only natural satellite
satellite
A moon, planet or machine that orbits a planet
or star
debris disc
A ring of rocky material orbiting a star or planet
Big Splash
A collision theory hypothesising how the Moon
formed
a) Impact winter – A long period of cold weather due to the impact of a large asteroid or comet on the
Earth's surface.
b) Mass extinctions – Events where large numbers of species become extinct in a short time.
6
Evidence from rocks; evidence from the movement of the Earth and Moon; evidence from observations
in the universe
7
a) both
b)
asteroid
c)
moon
d) moon
e)
asteroid
f)
both
8
The correct order is: B, C, A
9
Example answer – each point is worth 1 mark:
A stellar nebula can form from clouds of hydrogen gas in the universe.
Gravity pulls the atoms of hydrogen gas together into a huge ball. This ball is called a protostar.
The force of gravity continues to act on the gas atoms and squashes them closer and closer together.
This increases the pressure and temperature inside the ball.
Eventually, the pressure on the hydrogen atoms becomes so great that they fuse together to make
helium gas, releasing energy as heat and light. The ball begins to glow.
As the pressure continues to increase and more hydrogen is converted into helium, the ball starts to
shine. A main sequence star is ‘born’.
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