CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
ELS Workbook Answers
Unit 1 Respiration
c
Topic 1.1 The human respiratory
system
Exercise 1 Parts of the
respiratory system
a
respiratory system
b
trachea
c
bronchus
Exercise 1 Comparatives
d
larynx
a
more or greater
e
air sac
b
smaller
f
cartilage
c
smaller or less
g
vocal cords
d
more or greater or higher
h
bronchioles
e
less or smaller
Topic 1.3 Breathing
Exercise 2 Opposites
Exercise 2 True or false?
a
upside down
Aerobic respiration uses oxygen.
b
relax
✗ The vocal cords are not inside the
bronchus.
c
decreases
d
downwards
The plural of bronchus is bronchi.
e
inflates
a
✓
b
✗
c
d
✗
e
✗ The lungs contain air sacs.
Topic 1.4 Respiration
Topic 1.2 Gas exchange
Exercise 1 Using connecting words
Exercise 1 Observations, results,
conclusions and explanations
a
because
a
b
so
c
but
d
and
e
but
The limewater in the left-hand container did
not go cloudy.
After about 5 minutes, the limewater in the
right-hand container went cloudy.
The mouse appeared to be perfectly
comfortable.
b
The limewater in the right-hand container
went cloudy, but the limewater in the left-hand
container did not.
c
A respiring mouse produces carbon dioxide.
Exercise 2 Answering questions
1
Limewater changes from transparent to milky
white when carbon dioxide mixes with it. We
can compare the appearance of limewater that
has had inspired air bubbled through it and
limewater that has had expired air bubbled
through it.
a
haemoglobin
b
It moves by diffusion. The particles of oxygen
move randomly, and some of them cross from
the alveoli into the blood.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
d
Air is drawn into the left-hand container,
where all the carbon dioxide in it is absorbed.
The limewater in the left-hand container
checks that there is no carbon dioxide in this
air. The air passes over the respiring mouse,
and then into the right-hand container of
limewater. The carbon dioxide produced by
the mouse bubbles through the limewater and
makes it go cloudy.
Topic 1.5 Blood
Exercise 1 Writing sentences about
an analogy
a
They are both long tubes that a liquid can
flow through.
b
Blood vessels are soft and can change shape, but
a plastic water pipe cannot. Blood vessels are
made of living cells, but the water pipe is made
of plastic.
c
Blood is a liquid, so it can flow.
d
Blood contains red blood cells and white
blood cells, floating in a liquid called plasma.
Water does not contain cells.
Exercise 2 Modal verbs
a
must
b
must
c
must
d
might not
e
might or might not
Exercise 2 Vocabulary
2
Words
Meanings
blood plasma
a red substance inside red blood cells
red blood cells
microorganisms that cause disease
white blood cells
the liquid part of blood
haemoglobin
cells that help to destroy pathogens
oxyhaemoglobin
a bright red compound formed when oxygen combines
with haemoglobin
pathogens
chemicals, produced by white blood cells, that kill pathogens
phagocytosis
taking something into a cell and digesting it
antibodies
cells whose function is to transport oxygen
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Unit 2 Properties of materials
For example:
Topic 2.1 Dissolving
Exercise 1 Using prepositions
a
in
b
up
c
up, to
d
through
e
in
f
with
Exercise 2 Observations, results,
conclusions and explanations
a
She sees that the new reading on the scale is 52.5 g.
Mass before adding substance A = 49.5 g
Mass of substance A added = 3 g
Mass after adding substance A = 52.5 g
c
Mass is conserved when one substance
dissolves in another substance.
d
The particles of substance A spread out into
the spaces between the water particles. All the
particles are still there, so the total mass is the
same as the initial mass of substance A plus
the water.
Topic 2.2 Solutions and solubility
Exercise 1 The more . . . , the more
b
The higher the temperature, the more kinetic
energy the particles of solvent and solute have.
This means that the particles move around
faster. It is easier for the particles of solute to
spread into the spaces between the particles
of solvent.
c
A concentrated solution has a lot of solute
particles, compared to solvent particles. A
dilute solution has fewer solute particles
compared to solvent particles.
Topic 2.3 Planning a solubility
investigation
Exercise 1 Vocabulary for
planning experiments
a
the salts that they use
b
the mass of the salt that will dissolve in the
water
c
the temperature and the volume of water that
they use
d
balance
e
measuring cylinder
Exercise 2 Range, interval and units
a
25°C to 75°C
b
10 °C
c
measuring cylinder, cm3
d
thermometer, °C
e
(top pan) balance, g
a
more
b
less
c
less
d
more
e
less
Topic 2.4 Paper chromatography
f
more
Exercise 1 Putting words in the
correct sequence
Exercise 2 Writing two or more
sentences in an answer
Accept any two sentences that each contain
correct information. The information in the
second sentence should not simply reword what
is in the first sentence.
3
A saturated solution is one that contains the
maximum mass of solid that can dissolve. You
can make a saturated solution by adding a
solid and stirring, until there is some solid left
that will not dissolve.
She sees that the reading on the scale is 49.5 g.
She sees that all of substance A has
completely dissolved and forms a
transparent solution.
b
a
a
The chromatogram shows that this permanent
marker has three colours in it.
b
The solvent front is the highest level that the
solvent reaches on the chromatogram.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
c
I know that this dye is not a pure substance
because there are three different spots on the
chromatogram.
Exercise 2 Comparatives
and superlatives
d
The substance that is most soluble travels
furthest on the chromatography paper.
a
more
b
the most
c
fewer
d
further
e
the least
c
greater
d
greater, smaller
e
greater
Unit 3 Forces and energy
Topic 3.1 Forces and motion
Exercise 1 Opposites
a
When the forces on an object are unbalanced,
they can make it speed up or slow down.
b
The blue car is not moving because the forces
on it are balanced. The red car is starting to
move because the forces on it are unbalanced.
c
d
Topic 3.2 Speed
Exercise 1 Connecting words
a
The aeroplane stays at the same height above the b
ground because the force acting in the downward c
direction is equal and opposite to the force
d
acting in the upward direction (downward and
e
upward can be used in either order).
The spider moves at a constant speed because
the forward force produced by its legs is equal
and opposite to the backward force caused
by friction.
but
because
so
so
but
Exercise 2 The more . . . , the more
a
less
b
greater or faster
Exercise 2 Comparatives
c
slower or less
a
greater
d
greater
b
smaller
e
less
Topic 3.3 Describing movement
Exercise 1 Graph vocabulary
Words
Meanings
distance/time graph
draw a graph without putting numbers on the axes
x-axis
not moving
y-axis
the numbers on the axis of a graph
stationary
the bottom (across) axis on a graph
at rest
a graph showing distance plotted against time
sketch
the side (up) axis on a graph
scale
4
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Exercise 2 Describing graphs
a
the time in minutes
b
the distance travelled in metres
c
minutes
d
metres
e
A, B and C
f
B
g
B
h
A and C
Exercise 2 Writing two or more
sentences in an answer
Accept any sentence that answer each question,
and provide different information in each sentence.
For example:
Topic 3.4 Turning forces
Exercise 1 Prepositions
a
on
b
than, down
c
from
d
of
e
for
b
Arun pressing on the lever produces the
turning effect.
c
Sofia turns the brake lever and stops
the bicycle.
d
Multiplying force and distance calculates the
value of the moment.
e
Putting a heavier weight on this end balances
the seesaw.
f
We measure turning forces in newton metres.
b
You need to know the force that the object
produces, which is its weight. You also need to
know the surface area of contact between the
object and the floor.
c
The camel’s large feet have a large surface
area. This spreads the weight of the camel
over a larger area, so the pressure on the
sand is smaller.
Exercise 1 Putting words in the
correct sequence
There are various possibilities for some of the
sentences. Accept any sentence that has the
same meaning as the original, and uses only
an active verb.
For example:
Marcus turns the door handle.
The sharp knife has a smaller surface area. So,
using the same force, the pressure is greater
with the sharp knife.
Topic 3.6 Pressure in liquids and
gases
Exercise 2 Active and passive verbs
a
a
a
When you blow up a balloon, its volume
increases because there are more gas
particles colliding with the sides of the balloon.
b
The pressure on a submarine at great depth is
higher than the pressure at sea level.
c
The higher you go in the Earth’s atmosphere,
the less the pressure.
d
Atmospheric pressure decreases at
higher altitudes.
Exercise 2 Observations, results,
conclusions and explanations
a
Zara sees the water spouting out of the
container. The water from the top hole does
not arc outwards as far as the water from the
bottom hole.
b
The results are the measurements that
Zara made: 4 cm, 7 cm and 10 cm are the
distances travelled by the water spouts from
the side of the bottle.
c
Zara can conclude that the pressure in the
water is higher at the base of the bottle than
at the top; the deeper the water, the higher the
pressure.
d
The force produced by the weight of the water
above the lower hole is greater than that above
the top hole, making the pressure increase.
Topic 3.5 Pressure between solids
Exercise 1 Vocabulary
5
a
pressure
b
dividing, surface area
c
newtons (N)
d
sharp, blunt
e
pressure
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 3.7 Particles on the move
Exercise 2 Modal verbs
Exercise 1 Answering questions
a
might not
a
Sofia will see the red colour spreading
through the water.
b
should not
c
should
b
diffusion
d
might not
c
The particles in the red ink, and the particles
in the water, are in constant movement. They
move randomly. Over time, their random
movement causes them to spread out among
one another.
e
should
Unit 4 Ecosystems
Topic 4.1 The Sonoran Desert
Exercise 2 Active and passive verbs
Exercise 1 Vocabulary
a
Sofia can use a pitfall trap to catch beetles.
a
nocturnal
b
Marcus can use a book to identify these plants.
b
pollination
c
c
nectar
Mangroves provide a good habitat for
mud skippers.
d
adaptations
d
We/you can reduce risks by always working with
a partner.
e
ecosystem
e
f
ecology
We/you can take a photograph to record the
appearance of the plants.
g
habitat
h
cacti
Topic 4.3 Intruders in an ecosystem
Exercise 1 Modal verbs
Exercise 2 Singular and plural verbs
a
Species from one country should not be
introduced into another country, because they
can / might harm the native species.
b
Although everyone agrees that this introduced
species is harming our native species, some
people might not be happy for it to be killed.
c
If the introduced species is a predator, it might
eat the eggs of the native birds.
Topic 4.2 Different ecosystems
d
Introduced species cannot be eradicated easily.
Exercise 1 Completing sentences
e
As no words are given for learners to choose
from, they may select words that are not exactly
the same as those suggested here. Accept any
suitable words.
An introduced species can / might cause some of
the native species to become extinct.
Exercise 2 Prepositions
a
represent
b
interact
c
look
d
are
e
involve
The Arctic Ocean is covered with ice in the winter.
This provides a surface on which foxes and polar
bears can hunt for seals, which have to come to
the surface to breathe air.
Mangrove trees grow in sea water, along the coasts
of many tropical countries. Their leaves fall into the
mud, and provide food for prawns and crabs.
6
a
to
b
by
c
from
d
between
e
on
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 4.4 Bioaccumulation
Exercise 2 The more . . . , the more
Exercise 1 Positive or negative?
a
more
b
greater
c
greater
d
greater
e
less
a
b
Bioaccumulation means / does not mean the
increase in concentration of a substance as you
go up a food chain.
Biomagnification means / does not mean the
build-up of a substance in an organism’s body.
c
Persistent insecticides do / do not break
down easily.
d
All / not all insecticides are persistent.
e
All / not all insectides are biodegradable.
Unit 5 Materials and cycles on Earth
Topic 5.1 The structure of the atom Topic 5.2 Purity
Exercise 1 Connecting words
Exercise 1 Singular and plural verbs
a
because
a
b
but not
c
and
The reaction between silver nitrate and sodium
chloride does not / do not produce pure
silver chloride.
d
and
b
The water in all of these bottles is / are pure.
e
but
c
Marcus wears / wear safety glasses when doing
chemistry experiments.
d
About 68% of salt in seawater is / are sodium
chloride.
e
All pure diamonds is / are translucent.
Exercise 2 Answering questions
a
electrons
b
Neutrons and protons have the same mass.
Neutrons have no charge, but protons have a
positive charge. Electrons have almost no mass,
and a negative charge.
c
7
The number of protons and electrons is the
same. The positive charge of the protons is
cancelled out by the negative charge of
the electrons.
Exercise 2 Putting words in the
correct sequence
a
In some chemical reactions, only one product
is formed.
b
Universal indicator can tell us when the reaction
has formed a neutral product.
c
The reactions between some substances produce
impure mixtures of products.
d
All alloys are mixtures of two or more elements,
so they are not pure.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 5.3 Weather and climate
Exercise 1 Weather and climate vocabulary
Words
Meanings
weather
the study of weather
atmosphere
the average yearly patterns of temperature,
rainfall etc.
humidity
how far it is possible to see
visibility
numerical data that we can use to work out,
for example, the climate of a place
climate
how much water vapour is present
in the atmosphere
statistics
the temperature, rainfall etc. today or this week
meteorology
the air around us; the gases that
surround a planet
climatology
the study of climate
Exercise 2 Writing two or more
sentences in an answer
a
Climate is the long-term weather patterns in a
place. Weather is the day-to-day temperature,
rainfall and so on.
b
Answers will depend on what the weather is.
c
Direct rays from the Sun cause temperature
to increase. Taking temperature in the shade
ensures that the reading is comparable with all
other temperature readings, and is not affected
by how much direct sunlight is falling onto the
measuring instrument.
Topic 5.4 Climate and ice ages
Exercise 1 Completing sentences
As no words are given for learners to choose
from, they may select words that are not exactly
the same as those suggested here. Accept any
suitable words.
There is ice at both the North Pole and South Pole
today, so we know that the Earth is in an ice age.
However, the ice only covers the land quite close to
the poles, so we are in an interglacial period and not
in a glacial period.
8
Over the last 2 billion years, there have been
several ice ages. In each ice age, the climate has
cycled between glacial and interglacial periods.
Boulders that have been left behind by glaciers
provide evidence that the climate was much colder
in the past.
Exercise 2 Observations, conclusions
and explanations
a
There were pollen grains from plants adapted
to live in cold places near the bottom of the
core, and pollen grains from plants adapted to
live in warmer places near the top.
b
The climate was cooler in the past than it
is now.
c
The peat at the bottom of the core was laid
down longer ago than the peat at the top of
the core. So the pollen results show that the
plants that lived longer ago were adapted to
colder temperatures than the ones that lived
closer to the present time.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 5.5 Atmosphere and climate
Exercise 1 Vocabulary
Exercise 2 Writing sentences about
an analogy
a
biodegradable
Accept any suitable sentences, as long as they
contain correct ideas.
b
global warming
a
c
bioplastics
d
deforestation
Carbon dioxide keeps the Earth warm, just as
wrapping a blanket around you helps to keep
you warm.
e
renewable resource
b
f
fossil fuels
g
emissions
Carbon dioxide is a gas, but a blanket is solid.
Carbon dioxide is mixed up with all the other
gases in the atmosphere, but a blanket is a
single thing.
h
photosynthesis
c
i
locked up
Both the glass in the greenhouse, and carbon
dioxide, allow light energy to pass through
them, but stop heat from escaping.
j
recycled
Unit 6 Light
Topic 6.1 Reflections
Topic 6.2 Refraction
Exercise 1 Prepositions
Exercise 1 Refraction vocabulary
The incident ray reflects at / to the surface of
the mirror.
b
The incident ray is reflected by / onto
the mirror.
c
The reflected ray comes from / to the mirror.
Angle i is the angle of incidence and angle r is the
angle of refraction.
d
The mirror reflects the incident ray from / by
its surface
Exercise 2 Correcting statements
about refraction
e
The reflected ray travels onto / from the surface
of the mirror.
f
The normal is perpendicular at / to the surface
of the mirror.
There are several ways of writing a correct
statement. Accept any sentence that is
grammatically correct and makes a correct
statement. For example:
Exercise 2 Investigating reflection
9
When the incident ray hits the surface of the glass
block, it is refracted. The light ray is bent towards
line X. Line X is the normal. Line X is drawn at a
right angle to the surface of the glass block.
a
a
the angle of incidence
b
the angle of reflection
c
ray diagram
d
pencil, ruler and set square
e
protractor
a
When light passes from water into air, it
speeds up. Or When light passes from air into
water, it slows down.
b
When light passes from air into water, it is
bent towards the normal.
c
When light passes from one medium to
another, it sometimes bends towards the
normal, or sometimes away from the normal.
d
Lenses in glasses work by refracting light rays.
e
The angle of incidence is the angle between
the incident ray and the normal.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 6.3 Making rainbows
Exercise 2 Putting words in the
correct sequence
Exercise 1 Vocabulary check
ray box
a
Light is reflected at a mirror, and refracted
when it passes into a triangular prism.
b
As white light passes through a prism, blue
light is refracted more than red light.
c
Dispersion happens because refraction of some
colours of light is greater than others.
d
The range of colours we see when white light
is dispersed is called a spectrum.
D
red light
white light
spectrum
prism
blue light
Topic 6.4 Colours of light
Exercise 1 Vocabulary check
Words
Meanings
cyan
the three colours of light from which all other colours can be made
primary colours
a colour of light made by mixing red light and blue light
white
a colour of light made by mixing blue light and green light
magenta
a transparent object that lets some colours of light pass through, but
not others
yellow
light produced by mixing all the primary colours
coloured filter
a colour of light made by mixing green light and red light
Exercise 2 Writing about colours
of light
10
a
A green filter absorbs all colours of light
except green / red.
b
Topic 6.5 Galaxies
Exercise 1 Answering questions
a
gravity
A green filter transmits only red / green light.
b
It is a spiral.
c
All the colours except blue / green are
subtracted as light passes through a
green filter.
c
d
When green light shines on a red filter,
no / red light will pass through.
We are inside the galaxy, so we are looking
outwards through it. We are looking towards
the edge, so the stars look like a band across
the sky.
e
A yellow book looks yellow because it
absorbs / reflects yellow light.
f
A red book looks black / blue when we
shine blue light onto it.
Exercise 2 Modal verbs
a
can
b
cannot
c
can
d
might
e
might
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 6.6 Rocks in space
Exercise 2 Active and passive verbs
Exercise 1 Comparatives
and superlatives
a
Asteroids and planets orbit the Sun.
b
Small asteroids produce only a weak force
of gravity.
c
The impacts of asteroids produced the craters.
d
Rocks left over from the formation of the
Solar System formed asteroids.
e
Astronomers discovered the asteroid 2019
LF6 in 2019.
a
smaller
b
smaller
c
larger
d
smallest
e
larger
f
largest
g
greatest
Unit 7 Diet and growth
Topic 7.1 Nutrients
Exercise 1 Vocabulary
Accept any sentence that is grammatically
correct, has no spelling mistakes and contains
correct information.
a
protein
b
fats, carbohydrates
c
anaemia
d
oil
e
vitamins
Exercise 1 Using comparatives
and superlatives
f
minerals
a
younger, smaller, shorter or lighter
b
longer or thicker
c
older, taller
d
the man
e
the toddler
f
the man
Exercise 2 Singular and plural verbs
a
b
c
d
e
There is / are several types of nutrient that
we should eat each day.
Starch is / are a type of carbohydrate.
Both iron and calcium is / are important
components of our diet.
Carbohydrate and fat provide / provides us
with energy.
Fat stores beneath the skin provide /
provides insulation.
Topic 7.2 A balanced diet
Exercise 1 Describing a bar chart
a
b
c
d
e
11
Exercise 2 Writing sentences
the person
the number of megajoules of energy needed
each day
megajoules
0 to 12 (megajoules)
The different people are separate things.
There is not a continuous scale on the
horizontal axis.
Topic 7.3 Growth, development
and health
Exercise 2 Completing sentences
Smoking cigarettes can damage health. If a
pregnant woman smokes, she can harm the
development of the embryo, as well as damage
her own health.
Cigarettes contain a substance called nicotine,
which is addictive. Cigarette smoke also contains
tiny pieces of carbon, called particulates, which get
into the smoker’s lungs and damage the alveoli.
The gas carbon monoxide is also found in cigarette
smoke, and this reduces the ability of the blood
to transport oxygen. The tar in cigarette smoke
increases the risk of developing cancer.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 7.4 Moving the body
Exercise 2 Connecting words
Exercise 1 Prepositions
a
but
b
and
c
but
d
and
e
but
f
but
a
b
c
d
e
to
on
along
by
at
f
on, to
Unit 8 Chemical reactions
Topic 8.1 Exothermic reactions
Topic 8.2 Endothermic reactions
Exercise 1 Verbs with ‘out’
Exercise 1 Describing differences
a
give out
b
run out
Accept any sentence that is grammatically and
scientifically correct.
c
spread out
d
find out
e
carry out
f
spread out
a
Exothermic reactions produce a rise in
temperature, but endothermic reactions
produce a fall in temperature.
b
Accurate means that the measurement is what
it should be – for example, your arrows all hit
the middle of the target. Precise means that
all the measurements are very close to one
another – for example, all your arrows are
clustered together on the target.
c
Reactants are the substances that are present
at the start of a reaction. Products are the new
substances that are made during the reaction.
Exercise 2 Planning and doing an
experiment
12
a
preliminary work
b
the mass of magnesium ribbon
c
the temperature change
d
the concentration of the acid; the volume
of the acid
e
thermometer
f
°C
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Exercise 2 Results and conclusions
a and c
Liquid
Substance
added to
liquid
Initial
temperature
in °C
Final
temperature
in °C
Change in
temperature
in °C
Exothermic or
endothermic?
hydrochloric
acid
magnesium
ribbon
21
45
+24
exothermic
copper
sulfate
solution
magnesium
ribbon
20
28
+8
exothermic
water
potassium
chloride
21
19
–2
endothermic
vinegar
baking
powder
22
28
+6
exothermic
citric acid
sodium
hydrogencarbonate
solution
20
18
–2
endothermic
b
The right-hand (last) column.
Topic 8.4 Reactions of metals
with water
Topic 8.3 Metals and their
reactions with oxygen
Exercise 1 Comparatives and
superlatives
Exercise 1 Connecting words
Lithium, sodium and potassium are metals. They
each have a dull surface, but look shiny when they
are cut. The shiny surface goes dull after a while
because the metal reacts with oxygen in the air.
a
B
b
D
c
B and C
These three metals react quickly with oxygen, but
iron reacts more slowly because it is a less reactive
metal. Gold does not react with oxygen at all, so
we say that it is inert.
d
A and D
e
B, C, A, D
Exercise 2 Making predictions
Exercise 2 Modal verbs
a
b
c
d
e
can
must
can
can
must
a
It will not react.
b
It will react violently.
c
It will ‘pop’.
d
It will make it react faster.
Topic 8.5 Reactions of metals with dilute acids
Exercise 1 Writing word equations
a
b
c
d
e
13
magnesium + hydrochloric acid → magnesium chloride + hydrogen
magnesium + sulfuric acid → magnesium sulfate + hydrogen
zinc + hydrochloric acid → zinc chloride + hydrogen
zinc + sulfuric acid → zinc sulfate + hydrogen
lead + sulfuric acid → lead sulfate + hydrogen
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Exercise 2 Chemistry vocabulary
d
reaction
a
reagents
e
inert
b
reactivity
f
pure
c
salt
c
If you have a compass, you can always find out
in which direction you are facing.
d
Although we now have satellites to help us
to navigate, ships and aeroplanes still use
magnetic compasses.
Unit 9 Magnetism
Topic 9.1 Magnetic fields
Exercise 1 The more . . . , the more
a
b
c
d
stronger
weaker
stronger
stronger
Topic 9.3 Electromagnets
Exercise 2 Prepositions
Exercise 1 Different forms of the
same word
a
The field lines between a north pole and a
south pole all point in the same direction.
b
There is a force of attraction between the north
pole of one magnet and the south pole of
another magnet.
c
The magnetic field lines between two south
poles point away from each other.
d
The field lines between two like poles show
why the magnets repel each other.
e
The needle of a compass turns to point in the
direction of the magnetic field.
magnetic compass
It is made up of curving field lines that arc
between the north magnetic pole and the
south magnetic pole.
Geographic north is the northern point of the
Earth’s axis, on which it spins. Magnetic north
is where the magnetic pole of the Earth’s
magnetic field is.
Exercise 2 Putting words in the correct
sequence
14
a
The axis on which the Earth spins passes
through the geographic north and
south poles
b
We think that the Earth has a magnetic field
because its outer core is made of liquid iron.
b
magnet, magnetic
c
magnetic
d
magnet
e
magnetism
Accept any two sentences that are grammatically
correct and that answer the question. The second
sentence must contain information that has not
already been given in the first sentence.
For example:
Exercise 1 Answering questions
c
magnetise, magnet
Exercise 2 Writing two or more
sentences in an answer
Topic 9.2 The Earth as a
giant magnet
a
b
a
a
Wrap a coil of wire around a piece of soft iron.
Pass an electrical current through the wire.
b
Bring the north pole of a bar magnet towards
it. The end of the electromagnet that is
repelled by the north pole is its north pole.
c
It can be used for sorting scrap metal. The
electromagnet attracts iron and steel when
it is switched on, and then releases them
when it is switched off. This allows the
scrap metal to be lifted and moved from
one place to another.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021
CAMBRIDGE LOWER SECONDARY SCIENCE 8: TEACHER’S RESOURCE
Topic 9.4 Investigating
electromagnets
Exercise 2 Results and conclusions
a, b, c and d
Exercise 1 Planning and doing
an experiment
a
The more cells in the circuit, the greater the
strength of the electromagnet.
b
The number of cells in the circuit.
c
They can count how many paperclips their
electromagnet can attract and hold.
d
The number of coils; the core of the magnet;
the size and shape of the paperclips.
e
15
Number of coils
Number of
paperclips
0
0
5
2
10
8
15
12
20
19
The greater the number of coils, the stronger
the electromagnet.
Cambridge Lower Secondary Science 8 – Mary Jones & Sally Burbeary
© Cambridge University Press 2021