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A
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Stage
6

Dr Ivan Yow
Dr Loo Yoke Leng
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 Teachers and students have FREE access to the online textbook and workbook at
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Published by Alston Education Pte Ltd

to

627A Aljunied Road, #07-03 Biztech Centre, Singapore 389842

enquiry@alstoneducation.com
www.alstoneducation.com
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© 2022 Alston Education Pte Ltd

All rights reserved. No part of this publication may be

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reproduced, stored in a retrieval system, or transmitted

in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior
permission of the copyright owner.
)

Version 2023.2
(c

ISBN 978-981-4437-30-1

Publisher: Sim Wee Chee

www.AlstonDigital.sg
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Name:
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Class:
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 How to use the book
Hi, I am Cyrus!
CHAPTER
1 Gravity a
I love to experiment
nd Other
Every chapter begins with
The children
on water fro
are having
a competi
Forces and discover many

d
m one end tion. They
possible. Th of the tub need to mo

cool things about

ve an objec
an interesting problem ey are only to the other t
allowed to end as quick
use the ma ly as Can the fan
terials given help to move the
on the tab
scenario to spark learners’ le.

Science!
Which object objects across

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should we the water?

curiosity about the world choose to have

good chance of
a

around them. Learners are

winning?
Does the
material of the

required to weave all their object matter?

learning together to solve

this problem by the end of

te
the chapter. Why do you
think your chos
en
object will win?

I am in good
shape!

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What Will I Lea
rn Does the mass
Questions that guide learners
to think about the problem

on
Describe the of an object
difference bet
ween mass and determine if an
Describe gra weight.
The learning outcomes Draw force diag
vity and its effe

rams to show
ct. object floats or
sinks?
scenario and teach them how
each force act the name, size
covered are listed to offer Describe the
ing on an obje
effect of diffe
ct.
rent forces on
and direction
of
Does the
shape of
to make use of the concepts
an object
teachers and learners a clear learnt in the chapter to solve
Describe tha an obje ct. determine
t the mass and if an obje
floats or sinks. shape of an obje ct floats
ct can affect or
if it sinks?
overview of the chapter. Describe the
the problem.

ti
relative position
in the Solar Sys of the planets,
tem, and how the Moon and
they move. the Sun What forces need
to be balanced
for an object to
2 Chapter 1
float in water?
ca
Let’s investigate!
igate!
Let’s invest
1
Aim: To explo
re how the
strength of
gravity on
ight of an ob
ject.
different
Hey, I am Ada!
Experiments and activities t the we
I am always
n affec
planets ca
du

table below.
that precede formal content The strength of grav
ity on different plan
ets are given in the

curious about the

Uranus Neptune
Jupiter Saturn

teaching to allow learners to Earth Mars

Mercury Venus
Planet
86.8 102
1898 568

things around me.

Mass of the 0.642
actively explore key science 4.87 5.97
planet 0.330
(1024 kg) 11.0
9.0 8.7

concepts in the chapter.

23.1
Strength of 9.8 3.7

I like to use my
3.7 8.9
gravity
(N/kg)

Learners are encouraged

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1024 means

to infer concepts in their

that there are 24
zeros after 1. It is a
very big number!
gadgets to find
own ways to form their out more about
conclusions.
Science!
n

of gravity on the y-axis against the

h. Plot the strength
to

Sketch a scatter grap

Hello, I am Tim. mass of the planet
on the x-axis.
Other than mass,
ty is also

I like to gather information

the strength of gravi
variables.
affected by a few other
these other
You will learn about
r stages.
variables in highe

about Science and

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observe the world around

me. This is exciting!
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Gravity and Other

Forces 7

Other main features

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Retrace our steps Watch out! Think-Pair-Share

Questions that prompt Questions or statements that Questions that allow learners to
learners to recall prior highlight and clear common collaborate and discuss with one
knowledge to understand misconceptions, so that another. Learners can apply what they
a new concept. learners obtain a clearer have learnt and this facilitates a deeper
understanding of the topic. understanding of the concepts taught.

II How to use the book

 Colourful illustrations with
clear and easy-to-read
explanations that cover key Can we use physical prope
rties to identify changes in
states?
Evaporation
scientific concepts. This helps Boiling and evaporation are
both physical processes
where matters change
al process occurring is
Evaporation is the process
where liquid
How do we know if the physic change in state Gas particles
changes into gas. But this
to engage learners, allowing states from liquid to gas.
boiling or evaporation? Let
us comp are what happe ns to substances when
happens only at the surfac e of the liquid.
of water
vapour

evaporation.
them to grasp important

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they undergo boiling and When the liquid is exposed
to warmer
particles at the
surroundings, some liquid
concepts easily. y to escape
Boiling Watch out!
rising from a cup of hot
surface gain enough energ Liquid particles
We can sometimes see mist When this
Think-Pair-Share when we boil water. from the surface of the liquid. of water
tea. We also see similar mist chang es from liquid to
boiling or evaporating

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Boil some water. Observe. Can we tell if something is happens, water
of mist above a liquid? n at any
What happens when water based on the observation gas. Evaporation can happe
reaches its boiling point? below the boiling point.
temperature
Hello, I am Vera! Boiling occurs at a fixed tempe
a liquid boils, we can see bubbl
rature called the boiling point.
es forming throughout the
When
liquid as
nce in
es formed are the substa
I like to explore new es into gas. The bubbl
the liquid chang
gaseous state. We can use heat
a liquid to its boiling point.
Energy is needed to heat
places and learn about sources such as a heatin
g plate, stove or fire.

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the world around me. How do I know
if the water is
boiling?
The puddle of water
will disappear after

Let's go!
some time as water
During boiling, water evaporates.
We can hang our
turns into gas and rises During evaporation, wet clothes here!
to the water surface we can also observe mist
mist They will dry as water

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rising from the liquid. The
and escapes into the is the water vapour that
has evaporates from
them.
Mist surrounding air as condensed to form water
air.
hot water vapour. Hot droplets in the

water vapour is also

known as steam. When
and evaporation, the
the hot water vapour We can see that in both boiling
mist However, boiling occurs
loses heat to the cool liquid changes into a gas.
evaporation occurs on

on
surrounding air, it throughout the liquid while
only occurs at the
condenses to form tiny the surface of the liquid. Boiling
nce while evaporation can
Gas particles water droplets. This is boiling point of the substa
rature below the boiling point.
inside a bubble the mist that we see. occur at any tempe
Liquid particles
of water Physical Changes 63

Chapter 4
62

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Crack the case
Crack the case
A visually-appealing
mind map where
ca
undergoes
has Matter
Physical Changes
Physical properties learners can recall key
such as Can be reversible or not easily reversible
concepts and evaluate
their understanding of
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such as
___________
of a
___________at
which a substance
Changes in shape, Changes in
the chapter.
changes states Changes in
substance colour or texture states mixtures

Occurs at a specific
temperature
Occurs at any tem
perature
below boiling poin
t
Meow, I am Coco.
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Freezing or
solidifying Melting Let's embark on a fun
Liquid Solid
Occurs at ___________ or
Boiling Condensing and exciting journey
to learn Science!
___________ point (0 ºC) Solid Liquid
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Occurs at
Gas Liquid
___________
point (100 ºC)
shortest
Which item can Cyrus use to help the girls dry their gowns in the
to

time? Tick (🗸🗸).

blow
Set the hair dryer to its highest wind speed and hottest mode and Evaporating
it on the gowns. Liquid Gas
near
Turn the table fan on its highest wind speed and place the gowns
the fan. Occurs at the
Occurs throughout ___________ of the
Fan the gowns with the paper fan as quickly as possible.

Squeak! I am Momo!
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the liquid liquid

Blow at the gowns with all his might using his mouth and lungs.
Science keywords
Do you know, Science can be
kbook
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or
Consolidation worksheet
66 Chapter 4

A list of key scientific

Physical Changes
67

found everywhere, even in the

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vocabulary covered
smallest places! throughout the book.
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kboo
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Solve this! Science in context Clues or

Worksheet
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Follow-up questions Learners can link and Definition of Learners are directed to the
after every new apply their scientific challenging English relevant worksheets in the
concept for learners knowledge to real- words to aid learners' workbook, reinforcing their
to check their world contexts. understanding. understanding of concepts.
understanding and
build process skills.
How to use the book III
 Contents
Chapter 1
Gravity and Other Forces

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What is mass?

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What is weight?
How does gravity affect how objects in the Solar System move?
What are the effects of forces on objects?
What are the forces acting on objects in water?
What affects the amount of buoyant force acting on an object?

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What determines whether an object floats or sinks in water? 2

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Chapter 2
Respiratory and Circulatory Systems

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What is a body system?
What is the respiratory system?
What happens when we breathe in and out?

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What is the circulatory system?
What happens to our heartbeats and breathing when we exercise? 22
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Chapter 3
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Pathogens and Diseases

What are diseases?
What are the types of pathogens?
How do we control the spread of diseases?
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What are our body’s defence mechanisms against diseases? 36

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Chapter 4
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Physical Changes
What are physical changes?
What are some physical properties of substances?
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Do all substances change state at the same temperature?

Can we use physical properties to identify changes in states? 50
A

Chapter 5
)

Heat and Electricity

(c

How does heat energy get transferred?

How does electricity pass through a circuit?
How does the arrangement of components in
a circuit affect the brightness of a lamp?
What substances can conduct electricity? 68

IV Contents
 Chapter 6
Light

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What happens when light is reflected off an object?
What does the Moon look like on different days of the month?
82

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What happens when light travels through transparent and translucent objects?

Chapter 7

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Chemical Changes
What is a chemical reaction?

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What evidence can tell us that a chemical reaction has
taken place? 96

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Chapter 8

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Dissolving
Is dissolving a physical change or a chemical change?
How does temperature affect how solids dissolve in liquids? 108
ca
Chapter 9
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Rocks and Soil

How can we describe rocks?
What are the types of rocks?
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What is the rock cycle?

What are the layers of soil under the surface of Earth?
What is soil made up of?
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What are the different types of soil?

Are all soils good for growing plants? 120
to

Chapter 10
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Food Webs
How do food webs show interactions in an ecosystem?
A

How does energy flow in a food web?

How do human activities impact the ecosystem?
How do harmful substances affect living things in the food web? 144
)
(c

Chapter 11
Growing Up and Puberty
What is puberty?
What are the changes that occur during puberty?
What are the organs in our reproductive system?
160

Contents V
 Let's think and work like a scientist!
Modelling and
representation

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Models help us

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understand objects,
processes and
concepts that we
cannot easily see

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or touch. Models,
including diagrams,

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help us describe
scientific phenomena.

on
Half the moon will
always be lit up by the
Sun. But how much of

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that lit part do we see
each night?
ca
Safety Research
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Always get an adult’s help We can check secondary information

when handling heat, flames sources to research answers to our questions.
or electrical appliances.
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This website is an example of a

secondary information source. It shows
information that have previously been
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Use thermal insulators gathered from another person or source.

like rubber gloves when
to

handling heated materials

like heated metals.
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Will the lamp be brighter

in parallel or in series? Which
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variable in the circuit should I

change for my investigation?
)
(c

VI Think like a scientist

 Equipment
Choose the equipment with a scale and
unit that is most suitable for measuring

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the quantity. We can take repeated

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readings to reduce man-made errors
so that we obtain more reliable results.

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I am modelling
how metamorphic
rocks are formed
by applying

ti pressure and heat!

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We can build a model
to help us understand what
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happens to our lungs when

we breathe in and out.

Presenting and evaluating results

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We can present information using tables, bar charts, line graphs,

dot plots and scatter graphs.
n

The further you are

away from me, the Distance from your Number of
to

fewer water droplets classmate (cm) droplets

that land on you. Scatter graphs 20
Line of
best fit 40
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Dependent variable

Outlier 60
80
A

Achoo! 100
Points 120
)

140
(c

160
Independent variable
180
When drawing a line of best fit, ensure
that the number of points on both sides 200
of the line is the same and the points
should be at equal distances to the line.

Work like a scientist VII

 CHAPTER 1 Gravity and Other Forc
es
The children are having a co
mpetition. They need to mo
on water from one end of the ve an object
tub to the other end as quick Can the fan
ly as

d
possible. They are only allowe help to move the
d to use the materials given
on the table. objects across

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the water?
Which object
should we
choose to have a
good chance of

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winning?

Does the

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material of the
object matter?

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ca
Why do you
think your chosen
object will win?
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I am in good
shape!
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Does the mass

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What Will I Learn of an object

determine if an
Describe the difference between mass and weight.
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object floats or
Describe gravity and its effect. sinks?
A

Draw force diagrams to show the name, size and direction of

each force acting on an object. Does the shape of
an object determ
Describe the effect of different forces on an object. ine
if an object floats
)

or
Describe that the mass and shape of an object can affect if it sinks?
(c

floats or sinks.
Describe the relative position of the planets, the Moon and the Sun What forces need
in the Solar System, and how they move. to be balanced
for an object to
float in water?
2 Chapter 1
 What is mass?
Mass is a measure of how much matter an object has. It is measured in
grams (g) or kilograms (kg).

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We use a balance scale to measure mass.

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The mass of the
apples is 300 g.

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on
Balance scale

We can also use a weighing scale to tell us the mass of objects.

How heavy
ti This is another type
ca
am I? of weighing scale.
It shows the mass of
The weighing scale the flour. This is an electronic
shows that your weighing scale. It shows
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mass is 40 kg. the mass of the

apples.
E
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to

Think-Pair-Share
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Get four objects of different masses and estimate each mass. Use your estimates to
arrange them in order from the lightest to the heaviest. Then, place each object on a
A

weighing scale. Are your estimations correct? Present your findings using a bar chart.

To reduce errors in To find the average of

)

measurements, we can a set of readings, we sum

take repeated readings. up the readings and divide
(c

Then, we calculate the the sum by the number of

average. readings taken.

Gravity and Other Forces 3

 What is weight?

Watch out!
No, Tim. The weighing We use 'mass' to
scale does not measure your describe how heavy

d
mass. It measures your weight. something is, not 'weight'.
Tim, what is
The reading on the weighing Weight is the pulling force

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your mass?
scale displays your mass. due to gravity.

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I just used a weighing What is weight? Doesn't

on
scale to measure my 'weight' describe how heavy
mass. My mass is 40 kg. something is?

We learnt that gravity acting

on an object pulls the object
tiGravity is not a force. The effect of
ca
downwards, towards the gravity acting on an object gives
centre of Earth. the weight of the object.
du

The weight of an object refers to the downward pulling

force due to gravity. The weighing scale measures
the effect of gravity acting on the mass of an object.
E

It measures the weight of an object in newtons (N).

n
to

On Earth, the downward pulling force due to

gravity acts on the apples. This force is measured
by the weighing scale as weight but the reading
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shows its mass.

A

Gravity is a property
of anything that has
Weight of an object depends on gravity mass.
)

Anything that has mass can exert a pulling force due to

(c

gravity on another object. In general, the strength of gravity

is greater for objects with greater mass. Very massive
objects like planets, the Sun and the Moon have gravity
strong enough to pull other objects towards them.

4 Chapter 1
 We can also
say an object with
The strength of gravity that Earth exerts on a mass of 1 kg has
all objects is 9.8 N/kg. This means that an a force of 9.8 N
due to gravity
object with a mass of 1 kg on Earth has a acting on it.
weight of 9.8 N.

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The strength of gravity on the Moon is much lower than Earth’s gravity.

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An object on the Moon experiences less pulling force than on Earth. Hence, for
an object that has a mass of 1 kg on the Moon, the force due to gravity acting
on the object is much less than 9.8 N. So, for the same object, the weight of the

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object on the Moon is less than its weight on Earth.

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Weight of the object = Mass of the
Calculating the weight of an object object x Strength of gravity

The weight of an object depends on its mass and the

on
strength of gravity acting on it.

To calculate the weight of an object, we multiply its mass

by the strength of gravity acting on it.
ti
ca
My mass is 40 kg. 40 x 9.8 = 392 N
Your weight on My mass is still 40 kg.
du

What is my weight What is my weight on

Earth is 392 N. 40 x 1.6 = 64 N
on Earth? the Moon? Your weight on the
Moon is 64 N.
E

The strength of
gravity on the Moon
n

is 1.6 N/kg.
to
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A
)
(c

Tim's mass is the same on Earth 1

The gravity on the Moon is about 6 of
and on the Moon. This is because no the gravity on Earth. The weight of Tim on
matter has been added to him or the Moon will be 61 of his weight on Earth.
taken away from him.

Gravity and Other Forces 5

 Think-Pair-Share
1 What is the weight of each object in the previous Think-Pair-Share? Calculate. Arrange the
objects in increasing order of weight. Take the strength of gravity on Earth to be 9.8 N/kg.

d
Increasing weight

Lt
2 Compare the order of their weight and the The weight of an
order of their mass. What does this tell us object on Earth
about the mass and weight of objects on depends on its mass.
Earth?

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P
Solve this!

on
1 What is the unit of measurement for weight?
2 Describe the effect of the force due to gravity.

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3 Estimate the mass of a car and a bicycle. Calculate their weights on
Earth. Write down with the correct units.
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Worksheet 1

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Weight of objects on different planets
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Think-Pair-Share
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What happens to the weight What happens

of a car if it is on Mars? Will to the weight of
it be greater or smaller than
n

the same car What about

its weight on Earth? here? here?
to
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A
)
(c

Mars Jupiter Saturn

6 Chapter 1
 Let’s investigate!
1
rent
: To explore how the strength of gravity on diffe
Aim
weight of an object.

d
planets can affect the

Lt
The strength of gravity on different planets are given in the table below.
Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

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Mass of the
planet 0.330 4.87 5.97 0.642 1898 568 86.8 102
(1024 kg)

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Strength of
gravity 3.7 8.9 9.8 3.7 23.1 9.0 8.7 11.0
(N/kg)

on
1024 means

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that there are 24
zeros after 1. It is a
very big number!
ca
du
E

Sketch a scatter graph. Plot the strength of gravity on the y-axis against the
n

mass of the planet on the x-axis.

to

Other than mass,

the strength of gravity is also
affected by a few other variables.
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You will learn about these other

variables in higher stages.
A
)
(c

Gravity and Other Forces 7

 Questions:
1 a Analyse your graph for Mercury, Venus and Earth. What happens to the

strength of gravity on the planet as the mass of the planet increases?

Generally, as the _____________ of the planet increases, its strength of

d
gravity _____________.

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b Which planets do not follow the pattern described in a ?

2 A car with a mass of 1000 kg on Earth is brought to different planets. What

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happens to the amount of matter that the car has? Tick (🗸).
Decreases    Increases    Stays the same

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3 What is the mass of the car on each planet? Then, calculate the weight of

on
the car on each planet. Fill in the table below.

Planet Mass (kg) Weight (N) We have mass too.

We can exert a pulling

ti
Mercury force due to gravity on
Venus other objects around us.
ca
But the force we exert on
Earth 1000 9800
others is so small that it is
Mars not observable because
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Jupiter our mass is small.

Saturn
Uranus
E

Neptune
n

How does gravity affect how objects in the Solar System move?
to

Gravity causes planets to move around the Sun

Retrace our steps

ls

In the box on the

right, draw the planets
A

and the Sun in the Solar

System. Draw arrows
to show how planets
)

move in the Solar

(c

System.

The Sun is the largest object in the Solar System. It has the greatest mass
among the objects in the Solar System. Gravity on the Sun is much stronger
than the gravity on other objects in the Solar System.
8 Chapter 1
 Science in context
Spacetime
warp
Sir Isaac Newton explained that
there is a pulling force due to
gravity between objects. We can

d
Planets
measure the pulling effect of gravity

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acting on objects. This pulling effect
Sun
gives an object its weight. The unit
for gravity is Newton per kilogram

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Spacetime warp
(N/kg).

But Albert Einstein came up with a theory that describes gravity as an effect

P
that results from spacetime warp. The spacetime warp causes planets to move
around the Sun.

on
From both theories, we can say that gravity is a property of matter.

2 Let’s investigate!
ti
ca
t
form ation about the position and movemen
Aim: To find out more in
lar System.
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of the planets in the So

Instructions:
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1 Using the Internet or books, research and complete the table below.

Time taken to spin

Time taken to orbit the
n

Planet Distance from Sun (km) once about

Sun (days)
its own axis (h)
to

Mercury

Venus
ls

Earth 150 million 365 24

A

Mars

Jupiter
)
(c

Saturn

Uranus

Neptune

Gravity and Other Forces 9

 2 Present your results using bar charts. The x-axis represents the planets.
a

Distance
from the

d
Sun (km)

Lt
Planets

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b

Time taken

P
to orbit
the Sun
(days)

on
Planets

ti
ca
c
Time taken
to spin once
about its
du

own axis
(h)
E

Planets
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Questions:
to

1 What pattern can you notice about the time taken for a planet to orbit the
Reproduction process
Sun and
continues itspollination.
after distance from the Sun?
Petals of flower wither.
ls

2 Which planet takes the shortest time to orbit the Sun? Why?
3 Which planet takes the longest time to spin once about its axis? Compare
A

this to the time this planet takes to orbit the Sun. What pattern do you see?
)
(c

As the distance between a planet and the Sun increases, the time taken for the
planet to orbit the Sun increases too.

10 Chapter 1
 Earth is pulled towards
The strength of gravity on the Sun is the the Sun at a distance.
greatest since it has the largest mass. Earth So, Earth orbits
the Sun.
Hence, planets in the Solar System are
pulled towards the Sun.

d
This pulling effect of Sun’s gravity Sun

Lt
causes the planets to orbit the Sun.
These planets are known as Sun’s
At the same time,
natural satellites.

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Earth spins about
its own axis too.

Gravity causes the Moon to move around the Earth

P
The Moon is also a natural satellite. The Moon orbits Earth due to the pulling
effect of Earth's gravity on it. The Moon takes about 28 days to orbit Earth.

on
This period is called a lunar month.
While the Moon
orbits the Earth, it

ti
Sun spins about its own
axis too.
ca
Earth
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The lunar month is

used in many ancient
civilisations and some
E

calendars.

Moon
n
to

The Moon orbits Earth while Earth orbits the Sun.

ls

Solve this!
A

1 What causes the planets in the Solar System to orbit the Sun?
____________
)

2 Fill in the blanks.

(c

Earth ____________ about its own axis while it ____________ the Sun.
The Moon ____________ about its own axis while it moves around the
____________.
kboo
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or
Worksheet 2
W

Gravity and Other Forces 11

 What are the effects of forces on objects?
Retrace our steps
In real life, many forces can act on an object at the
same time. Weight is just one of the forces. Which arrow represents

d
a larger force? Circle.
To predict the effect of the forces on an object, we

Lt
need to think about the size and the direction of
each force. Which arrow represents a
downward force? Circle.

te
Can cause an object to remain at rest
What are the forces acting on an object at rest?

P
on
A trophy that is not We can use a
moving is at rest. We can force diagram to
also say it is stationary. represent the forces
The table exerts a normal acting on an object.

ti
force on the trophy to
support the trophy.
ca
Normal force
du
E
n

Weight
to

A trophy at rest on the table

experiences a downward
pulling force due to gravity.
ls

The trophy exerts its weight

on the table.
A
)

The size of the normal force is the same as the size of the weight of the trophy.
(c

We say that the forces acting on an object at rest are balanced.

12 Chapter 1
 Can cause an object to change shape

Think-Pair-Share

Hold a piece of paper. What will happen if you apply a force to fold, tear or crumple the

d
paper? How are the forces acting in each situation?

Lt
te
P
on
When we fold a piece of When we tear a piece of When we crumple a
paper, we push the two parts paper, we pull the paper in piece of paper, we push
of the paper towards each opposite directions. the paper towards a

ti
other. centre point.
ca
A force can change the shape of an object.
du

Solve this!

Draw and label the forces acting on each object below.

E

1 2
n
to
ls
A

Folding a T-shirt A box that is stationary

)
(c

Gravity and Other Forces 13

 Can cause an object to accelerate
When a force is applied to an object at rest such that the forces acting on
the object become unbalanced, the object starts to move. When an object

d
at rest starts to move in the direction of the applied force, we say the object
accelerates from rest.

Lt
When an object moves, there is friction between the object and the surface
that is in contact with the moving object. This causes the object to slow down.

te
When an additional force greater than friction is applied to a moving object,
it will cause the object to move faster. We say that the object is accelerating

P
and its speed is increasing.

on
I can make
the hockey puck
accelerate by

ti
applying more
force to it!
ca
du

Applied
force
E

Friction

I can change the

n

direction of the
puck by hitting
to

it at a certain
angle!
Applied
ls

force Direction of
moving object
A

Movement

Friction
)

Friction
(c

Can cause a moving object to change direction

A force applied at an angle can change the direction of a moving object.

14 Chapter 1
 Can cause a moving object to decelerate
When we stop applying force to a moving object, friction continues to act
against the moving object. If friction is greater than the force applied, the

d
unbalanced forces will cause the object to slow down. We say that the
object is decelerating and its speed is decreasing.

Lt
If we apply a force in the opposite direction to the moving object, it will slow
down too. Both friction and an applied force in the opposite direction to the

te
movement of the object can cause the moving object to decelerate.

P
on
ti
ca
du

Applied
force
E

If the force applied in the

opposite direction is great
enough, it may stop the
moving object immediately.
n

A moving object slows

down and comes to a
to

stop after some time due

to friction.
ls

Friction
A

Think-Pair-Share
)

What can happen to a moving object after some time? Can an object continue moving
(c

without coming to a stop?

Clues Speed – How fast an object moves

Gravity and Other Forces 15

 Solve this!

The arrows below represent the amount of forces applied by Tim and Cyrus
on a stationary box.

d
Cyrus Tim

Lt
te
P
on
1 What will happen to the box? Circle.
The box will ( accelerate / decelerate ) from rest and move towards
( Cyrus / Tim ) .

ti
As the box is being moved by Tim and Cyrus, Ada comes in to help Cyrus and
ca
2

applies the same amount of force as Tim. How will the box move now?
________________________________________________________________
du

kboo
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or
Worksheet 3

W
E

Think-Pair-Share

Look around you. Can you identify the forces around you? What are the effects of these forces?
n

What are the forces acting on objects in water?

to

What forces keep the ball

ls

floating in water? What

do you feel when you try
to push it deeper into the
A

water?

To update
)

There are two forces acting on objects

(c

in water — the weight of the object and

upthrust. An upthrust is also known as a
buoyant force.

16 Chapter 1
 Gravity acts on all objects, including objects in water.
All objects exert a downward force due to gravity, Buoyant force

even in water.

d
Buoyant force is the upward force exerted by water
on objects. It acts against the weight of the object.

Lt
When we put an object in water, it pushes away Weight

some water to make space for itself. We say that

te
the object displaces water.

The size of the buoyant force acting on an object is equal to the weight of the

P
water displaced by the object. The weight of the water displaced depends on
the volume of water displaced.

on
ti
ca
du

Displacement
can

Water Buoyant
Buoyant
E

force Measuring
Wooden force
cylinder
block
n
to

The volume of water displaced is measured using the measuring cylinder.

The greater the volume of water displaced by the object, the greater the
ls

weight of the water displaced. This shows that there is a greater amount of
A

buoyant force acting on the object.

)
(c

Clues Displace – To take the place of something

Gravity and Other Forces 17

 What affects the amount of buoyant force acting on an object?

3 Let ’s investigate!

d
the amount of
Aim: To find out how the shape of an object affects

Lt
buoyant force acting on it.

Instructions:

te
1 Place a ball of clay on the weighing scale.
Clay ball
Reading: __________

P
Displacement
can
Calculate its weight: _________ N
Measuring
Water cylinder

on
2 Set up the materials according to the
diagram on the right.
Wooden

ti
block
3 Lower the clay ball into the displacement
Weighing
can. Did it float or sink? _________ scale
ca
4 Record the volume and mass of water collected in the measuring cylinder.
Calculate the weight of the water. Fill in the table below.
du

5 Flatten the ball of clay and reshape it into a bowl. Lower the clay bowl into
the displacement can. Did it float or sink? _________
E

6 Record the volume and mass of water collected in the measuring cylinder.
n

Calculate the weight of the water. Fill in the table below.

to

Volume of water in Mass of water in Weight of water in

Clay Weight of clay (N) measuring cylinder measuring cylinder measuring cylinder
(__) (___) (N)
ls

Clay ball
in Step 4
A

Clay
bowl in
Step 6
)

Questions:
(c

1 Compare the volume of water collected in the measuring cylinder in Step 4

and Step 6. How did it change?

2 What does the volume of water in the measuring cylinder indicate?

18 Chapter 1
 3 Compare the weight of water collected in the measuring cylinder in Step 4
and Step 6. How did it change?

4 Which property of the clay was changed when you reshaped it in Step 5?

d
Circle.

Lt
( Mass / Shape / Weight ) of the clay

5 What can you infer about the volume and weight of water displaced when

te
the ball of clay was reshaped? Circle.

P
When the ball of clay was reshaped into a bowl, the volume of water
displaced ( increased / decreased ). The weight of water displaced

on
(increased / decreased ).

Conclusion:

ti
Changing the ________________ of an object may ________________ the
ca
volume of water displaced by the object when it is in water.

When the volume of water displaced by the object in water ________________,

du

the weight of water displaced by the object ________________. This tells us

that the amount of buoyant force acting on the object ________________.
E

Changing the shape of an object can affect the volume of water displaced by
n

the object. We can infer the amount of buoyant force acting on the object in
to

water by observing the volume of water displaced.

If two objects have
the same mass and weight but
Clay bowl
ls

Clay ball displace different volumes of

water, we look at their shapes.
Objects with certain shapes can
A

displace a larger volume of water,

telling us that there is a greater
amount of buoyant force
)

acting on them.
(c

Buoyant force Buoyant force

The clay ball displaces less water than the clay bowl. This means
that the clay ball experiences less buoyant force than the clay bowl.
Gravity and Other Forces 19
 What determines whether an object floats or sinks in water?
Think-Pair-Share

d
Lt
Metallic boat
Wooden ball Metal ball Plastic ball

Is it true that all

te
The objects above heavy objects will
have different sink? What about a
weights. If they metallic boat? Does it

P
are placed in water, float or sink?
will they float or sink?
Why?

on
The weight of the object and the size of the buoyant force acting on it in water

ti
can determine if an object floats or sinks in water. Buoyant force = Weight of bowl
ca
Balanced forces — Float
An object floats when the buoyant force acting on it
du

is equal to the weight of the object. The forces acting

on the object are balanced. The clay bowl floats.

Buoyant force < Weight of ball

E

Unbalanced forces — Sink

An object sinks when the buoyant force acting on it is less
n

than the weight of the object. The forces acting on the

object are unbalanced.
to

The clay ball sinks.

Solve this!
ls

Vera places a steel ball and a plastic ball into a beaker of water. The steel ball
weighs more than the plastic ball. Her observations are shown below.
A

1 Draw the forces acting on each ball. Explain why

Plastic
each ball sinks or floats.
)

ball
(c

Steel 2 Vera places a steel toy ship into the

ball same beaker of water. It floats!
If the toy ship weighs the same as
the steel ball, why does it float? or
kboo
k
Worksheet 4
W

20 Chapter 1
 Crack the case
Normal force
Friction
Applied force
Gravity Types

d
Has a pulling effect on objects

Lt
Forces
 A property of any object with
___________

te
causes
Effects
can cause
Planets to

P
_________ An object
the Sun An object

on
gives
to change
to remain ___________
an object
its stationary or at

ti
___________
An object
to change
ca
Buoyant
Weight ___________
force An object
acts on to___________
du

Objects in water as its speed An object to

increases ___________ as its
speed decreases
E

Forces are Forces are

n

unbalanced ___________
to

team choose so that

Which object should Tim’s
(🗸).
they can win? Why? Tick
e buoyant force is
ls

3 kg steel ball because th

e steel ball will float.
less than its weight. So, th
A

e the volume of
1kg wooden boat becaus
r, giving a greater
water displaced is greate
the wooden boat
)

amount of buoyancy. So,

Object _____ Object floats
(c

will float.
e volume of water
1kg steel boat because th
g a greater amount
displaced is greater, givin
kboo
k
or
Consolidation worksheet
l boat will float.
W

of buoyancy. So, the stee

Gravity and Other Forces 21
 CHAPTER 2 Respiratory and Circula
tory Systems
Ada participated in a runnin
g race at school. At the end
Ada feels tired and she can of the race,
feel her heart beating very qu

d
She is also breathing faster ickly.
than usual.

Lt
te
P
Is there something
wrong with me? My heart

on
does not usually beat this
fast and I find it difficult to
catch my breath!

ti
ca
du
E
n

Ada has another race to co

mpete
to

later but she is worried abou

t her
health. What should Ada do
?
ls

What are the

functions of the What does Ada's
A

What Will I Learn heart and lungs? body require mor

e
✓ Describe how the human respiratory system works. of during her run?
)

✓ State that many vertebrates have a respiratory

system similar to that of ours. What happens to Ada's
(c

heart rate and breathing

✓ Describe the human circulatory system and its function.
rate when she runs?
✓ State that many vertebrates have a circulatory How do her heart and lungs
system similar to that of ours. work differently when she
is running or at rest?

22 Chapter 2
 What is a body system? Retrace our steps

When two or more organs function and work Can you name a
body system and
together, they form a body system. Our body some of its organs?
has different types of body systems to carry out

d
How do these organs
different functions. Body systems in living things work together in our

Lt
body?
work together to help us carry out different life
processes, including obtaining oxygen and nutrients
and removing waste materials from the body.

te
There are different
What is the respiratory system? gases present in the air.
We can use percentage

P
We breathe in or inhale air into our body. (%) to show how much
We breathe out or exhale air out of our body. of each gas is present
in the air.

on
Gas Inhaled air Exhaled air
Carbon dioxide 0.04% 4%
Oxygen 21% 16%
Water vapour 0.5%

ti 5%
ca
More oxygen is found in inhaled air than exhaled air. More carbon
dioxide and water vapour are found in exhaled air than inhaled air.

When we inhale air, oxygen is taken in so that it can be used by our

du

body. When we exhale air, carbon dioxide and water vapour produced
by our body are removed from our body.
Our body does this through the respiratory system.
E

Our respiratory system consists of a network of organs to help us

inhale air and to move oxygen from the air that we breathe in into our
n

blood. Our blood then transports oxygen to different parts of our body.
to

Parts of the respiratory system

ls

Think-Pair-Share

Using the Internet or books, research to find out about the organs that make up the
A

respiratory system.
Questions:
)

1 What organs form the respiratory system?

What function does each organ have?
(c

3 How do they work together to help the body take in oxygen from the air?

Draw a poster to show an outline of a human body and the organs of the respiratory
system. Label each organ and describe its function.

Respiratory and Circulatory Systems 23

 1  o take in oxygen
T
from the air,
humans inhale air

d
through the nose
or the mouth.

Lt
Nose
2 A
 ir travels down
the trachea and
3 T
 he bronchi Mouth into the bronchi.
connect to the

te
lungs within
the chest. The Trachea 4 T
 he airways of the
right bronchus bronchi branch out

P
connects to the to form narrower
Bronchi
right lung while airways in the lungs
the left bronchus called bronchioles.

on
connects to the Air from the
left lung. bronchi enters the
bronchioles.
5 A
 t the end of
the bronchioles
ti Bronchioles
ca
are tiny air sacs
Lungs are not empty
called alveoli.
sacs. They contain
Air from the
du

tree-like structures with

bronchioles many tiny alveoli. The alveoli
enters the alveoli. Bronchiole
Diaphragm increase the surface area
It is a muscle to absorb oxygen and
E

below the lungs. remove carbon dioxide.

Alveoli
n

Alveolus
Air in and
Blood
out
to

Carbon vessels
dioxide

E
 ach air sac, known as an alveolus, is
ls

6
Oxygen surrounded by many small blood vessels
which transport blood. Oxygen travels
A

through the thin walls of the alveoli and

blood vessels into the blood.
Here, oxygen is transported from the lungs
)

into the blood. At the same time, carbon

Blood vessel
(c

dioxide is transported from the blood to the

Inside an alveolus lungs to be removed as waste product.
and a blood vessel

Bronchus – A large airway that leads from the trachea to a lung. The plural of
Clues
bronchus is bronchi.

24 Chapter 2
 Respiratory system in other vertebrates
Many vertebrates have a similar respiratory system to a human's.

Lung

d
Lt
te
P
Lung

Lung

on
ti
ca
du

How are the respiratory system of mammals, reptiles and birds similar to ours?
E

Think-Pair-Share

Do all animals have a similar respiratory system to a human's? Using the Internet or books,
research and compare the respiratory system in humans and animals. Present your findings
n

using labelled diagrams to your classmates.

to

What happens when we breathe in and out?

ls

1 Let ’s investigate!
A

diaphragm moves.
Aim: To find out what happens to our lungs when our
)
(c

Materials:
 A clean and dry A straw Rubber band
plastic bottle Scissors Plasticine
Two balloons Sticky tape
Respiratory and Circulatory Systems 25
 Instructions:
1 Use scissors to cut and remove the 2 Stretch the remainder of the balloon
bottom of a plastic bottle carefully. over the bottom of the cut bottle
Then, cut and remove the rounded and secure it in place using tape.

d
end of a balloon. This is Balloon A and it represents

Lt
Scissors the diaphragm.
Balloon

te
Balloon A
Plastic bottle

P
Sticky tape

3 Insert a straw inside another 4 Place the straw and Balloon B from

on
balloon and tie them together Step 3 inside the bottle in Step 2.
using a rubber band. This is Balloon Hold the straw in place at the mouth
B and it represents the lung. of the bottle using some plasticine.
Straw

ti Plasticine
ca
Rubber
band Balloon B
du

Balloon B
Balloon A

Balloon B
E

5 Carefully move
Balloon A up and down Balloon A
n

by pushing and pulling. Push

to

Pull

Questions:
ls

1 As you pull Balloon A, what do you observe about Balloon B?

_________________________________________________________________
A

2 When you push Balloon A into the bottle, what do you observe about Balloon B?
_________________________________________________________________
)

3 What does this model tell you about our lungs when our diaphragm
(c

moves? Circle.
When our diaphragm moves downwards, our lungs become ( smaller / bigger ).
When our diaphragm moves upwards, our lungs become ( smaller / bigger ).

26 Chapter 2
 When we inhale, the diaphragm flattens and moves downwards. The lungs
have more room to expand. The lungs become bigger and air rushes into the
lungs. When we exhale, the diaphragm moves upwards and the lungs become
smaller. Air is pushed out of the lungs.

d
Air Air

Lt
Trachea

te
Lung

P
Diaphragm

on
flattens and Diaphragm
moves downwards moves upwards
When we inhale When we exhale

ti
Solve this!

Label the diagram using the helping words below.

ca
Alveolus  Bronchiole  Diaphragm  Bronchus
Lung  Mouth  Nose  Trachea
du
E
n
to
ls
A
)
(c

kboo
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Worksheet 1
W

Respiratory and Circulatory Systems 27

 What is the circulatory system?
Parts of the circulatory system How do you think
blood moves in
our body?
What happens

d
when oxygen from
the lungs enters

Lt
the blood?

Oxygen is required in different parts of the body. From the lungs, oxygen is

te
transported into the blood. The circulatory system is the transport system
that circulates blood to the different parts of our body. Other than oxygen,

P
the blood also transports nutrients to parts of our body. Carbon dioxide and
other waste products are also transported by the blood so that they can be

on
removed from our body.

Heart Blood vessels

ti
The heart is a Blood vessels are tiny tubes which carry blood around our
muscular pump that body. The three main types are arteries, veins and capillaries.
ca
helps to pump blood
around our body. Arteries carry blood
away from the heart.
du

They are usually thick

and muscular.
E

Veins carry blood back

to the heart.
n

Capillaries Artery
to

Oxygen
Vein
ls

Blood
Blood contains
Red
many components Capillaries are very thin and tiny blood
A

blood cell
including red blood vessels that allow materials to move in
cells. and out of the blood.
Red blood cells in the Oxygen, nutrients, water and waste
)

blood carry oxygen to materials can easily pass through the

(c

the different parts of capillaries between the blood and the

the body. organs.

Clues Circulate – To move around from one place to another along a path

28 Chapter 2
 Transport of oxygen and carbon dioxide in the circulatory system

5 The heart pumps Artery carrying Vein carrying 1 Veins carry blood rich
blood rich in carbon blood rich in blood rich in in oxygen from the
dioxide to the lungs. carbon dioxide oxygen lungs to the heart.

d
The arteries carry blood
rich in carbon dioxide

Lt
to the lungs. At the
2 The heart pumps
lungs, carbon dioxide is blood rich in oxygen
Lungs through the arteries
removed from our body
to the capillaries

te
when we breathe out.
within the organs of
the body.

P
Blood passes through the 3 At the capillaries,
heart twice in each round
oxygen and nutrients

on
of circulation. The first
time, the blood enters the are transported
heart to be transported from the blood to the
to other parts of the body. organs. Oxygen and

ti
The second time, blood nutrients are needed
enters the heart to go to in all parts of the
the lungs. We say that body for respiration
ca
humans have a double to occur. This process
circulatory system. Heart
releases energy and
produces waste
du

materials. Waste
materials like carbon
dioxide and water
E

Artery
are transported from
Vein carrying blood rich Other
in carbon dioxide carrying the organs to the
parts of blood through the
blood rich
n

body
4  lood rich in carbon
B in oxygen capillaries.
dioxide is carried from
to

the capillaries to the Respiration is a chemical process which

veins. The veins carry takes place in living things. This is the
blood rich in carbon chemical reaction:
ls

dioxide back to the heart. Oxygen + Nutrients ➝ Carbon dioxide +

Water + Energy
A

Watch out!

Breathing is not the same as respiration! Breathing is the physical process

whereby air moves in and out of the lungs. Respiration is a chemical process
)

which takes place in the cells of living things. Respiration uses the nutrients
(c

absorbed by the body and oxygen taken in during breathing to produce

energy for our daily activities.

Clues Cell – Smallest unit that makes up all living things

Respiratory and Circulatory Systems 29

 Think-Pair-Share
Retrace our steps
Push a toothpick halfway into a Be careful when
marshmallow. On the other end of the you are pushing the
toothpick, paste a sticker. Rest your arm toothpick into the How does the

d
on a table with your palm facing upward, marshmallow! heart circulate
with the marshmallow placed on the blood around the

Lt
inside of your wrist. body?

What do you observe about the sticker?

Using your understanding of the heart,

te
discuss the explanation for your
observation.

P
When I place my I can feel

on
hand on my chest, something beating
I can feel my heart on my wrist too!
beating. The beats you feel
on your wrist are your

ti
pulse. Each time your
heart beats, you can
feel it on your wrists and
ca
some other parts of
your body.
du
E

Your heart rate is the

number of times your
n

heart beats in one

Think-Pair-Share
minute.
to

Feel the pulse on your wrist by placing two fingers on the palm side
of your wrist.
How many times can you feel your heartbeat in 30 seconds?
ls

Now, calculate your heart rate (number of heartbeats in 30 seconds x 2).

My heart rate: _________ beats per minute
A

Compare your heart rate with your classmates.

Do you have the same heart rate? What does your pulse tell you about how
fast your heart is pumping blood in your body?
)
(c

Think-Pair-Share

Using the Internet or books, research to find out which living things have circulatory systems
similar to ours. How are they similar to us?

30 Chapter 2
 Circulatory system in other vertebrates
Many vertebrates have a similar circulatory system to a human's too.

d
Similar to

Lt
humans,
vertebrates
like us have
a heart too.

te
P
on
ti
We also have
blood and blood
vessels!
ca
du

Science in context
E

I am a cardiologist. I am a pathologist.
I treat patients with
n

In the 17 century, English

th I test the blood to find
heart diseases. out more information
physician William Harvey
to

discovered that the heart about the patient’s

is responsible for pumping health.
blood to other parts of the
ls

body.
A
)
(c

Respiratory and Circulatory Systems 31

 What happens to our heartbeats and breathing when we exercise?

Retrace our steps

2 Let ’s investigate!

d
s How do you think
Aim: To find out if our heart rates and breathing rate our heartbeats and

Lt
change during exercise. breathing change
during exercise?

Instructions:

te
1 At rest, measure your heart rate by checking your pulse. Use a stopwatch

and count the number of beats you feel in a minute.

P
2 Use a stopwatch and count the number of breaths you take in a minute.

on
3 Record your heart rate and breathing rate in the table below.
4 Exercise by running or sprinting for 5 to 10 minutes.
5

ti
Repeat Steps 1 to 3 immediately after exercising.
This will be your heart rate and breathing rate
Breathing rate refers to the
number of breaths we take
ca
in one minute.
immediately after exercise.
After 5 to 10 minutes of rest, repeat Steps 1 to 3.
du

This will be your heart rate and breathing rate

5 to 10 minutes after exercise.
E

Heart rate (Number of beats Breathing rate (Number of

in one minute) breaths in one minute)
n

Before the exercise

to

Immediately after
exercise
ls

5 to 10 minutes after
A

exercise

Questions:
)

1 What do you notice about your heart rate and breathing rate before and
(c

immediately after the exercise?

2 What do you notice about your heart rate and breathing rate 5 to

10 minutes after the exercise?

32 Chapter 2
 When we exercise, our heart rate and breathing rate increase. Our muscles
need more energy to cope with the activity. So, our body needs more oxygen
than normal for respiration to release more energy to our muscles.
This requires our body to take in more air containing oxygen so our breathing

d
rate increases. Our heart pumps faster so that more blood with oxygen gets

Lt
transported to parts of our body, including our muscles. At the same time, the
blood transporting carbon dioxide gets transported back to our heart faster.
So, our heart beats faster.

te
When we stop exercising, our body does not need more oxygen than usual.
Our breathing rate and heart rate will decrease and eventually return

P
to normal.
Check out how our respiratory

on
and circulatory systems work
together by watching this video.

Solve this!

ti
Match each part of the circulatory system to its function.
ca
Allows the exchange
Artery
du

of materials in and out

of the blood
E

Carries blood away

Blood
from the heart
n

Contains oxygen,
to

Capillary nutrients and waste

materials
ls

Carries blood towards

A

Heart
the heart
)
(c

Pumps blood around

Vein
the body

kboo
k
or
Worksheet 2
W

Respiratory and Circulatory Systems 33

 Crack the case

Respiratory system

d
Lt
consists of

In many vertebrates,

te
these systems are
Nose or mouth
similar to a human's

P
on
Trachea

ti blood rich in
ca
___________ ______________

Lungs Heart
du

___________ blood rich in

E

______________
n

___________ which __________ blood

to

are tiny air sacs around the body

surrounded by
ls

___________
A

Move oxygen from the

)

air into our blood

(c

34 Chapter 2
 Circulatory system

d
Lt
Carry blood _________
consists of Arteries the heart

te
Carry blood _________
Veins the heart

P
Blood vessels

on
Allow the
__________ blood Capillaries __________________
around the body in and out of the blood

blood rich in to
ti
ca
______________
where Oxygen and nutrients
Organs in the body
du

are required so that

respiration can occur.
blood rich in
E

______________
n
to

ha t ca n Ada do af ter he r running race? Tick (🗸).

W
du ce he r heart rate and breathing rate.
ls

to re
To rest after her first race
rate and
ex ercis e afte r he r first race to reduce her heart
Continue to
A

breathing rate.
t to pa rticipat e in a cy cling competition instead.
To not run bu
)

health.
as running is harmful to her
(c

rticip ating in ru nn ing

To stop pa

kboo
k
or
Consolidation worksheet
W

Respiratory and Circulatory Systems 35

 CHAPTER 3 Pathogens and Disease
s

d
Lt
te
P
Get well soon,
The doctor said that Vera!
I have caught the
common cold.

on
ti
ca
du

I don’t feel so good after

E

I visited Vera. Do you mind

passing me the homework for
today’s lessons?
n

Tim wants to pass the home

to

work to Ada.
However, he is worried that he
might fall
sick like Vera and Ada. What
should he do?
ls

What happene
What Will I Learn d
A

to Ada? Why d
id
Describe how some diseases can be caused by infection with this happen?
pathogens that can be passed from one host to another.
)

What type of
Describe how good hygiene can control the spread of diseases
pathogen causes
(c

and describe ways to avoid being bitten by insect vectors.

the common cold?
Describe the defence mechanisms humans have against
infectious diseases.
How is this
pathogen
transmitted?
36 Chapter 3
 What are diseases?
Infection can spread from one living thing to another. Retrace our steps
Infections are caused by small organisms called
pathogens. Some examples of pathogens are viruses, What are some

d
infectious diseases
bacteria, parasites and fungi. that can affect

Lt
Infections caused by pathogens can result in diseases animals?
called infectious diseases. Infectious diseases can
cause discomfort, illnesses or even death.

te
P
1 Let ’s investigate!

the pathogens

on
Aim: To research common infectious diseases and
that can cause them.

Instructions:
ti
ca
1 Using the Internet or books, research an infectious disease that can

be caused by viruses, bacteria, parasites or fungi. Use the questions in

the table below to guide your research.
du

Pathogen Viruses Bacteria Parasites Fungi

Disease that they
can cause
E

How dangerous is
this disease?
n

Do they spread
through air, touch
to

or insect bites?
Which part of
the body does
this disease
ls

commonly affect?
How can this
A

disease be
treated or
prevented?
)

2 You can present your findings by designing fact cards. Discuss your
(c

findings with your classmates.

Disease – A condition where the organs or systems of a living thing are

Clues damaged or not functioning as they normally should

Pathogens and Diseases 37

 What are the types of pathogens?
Different types of pathogens can cause different infectious diseases. When
a pathogen from one living thing infects another living thing, we say that the
infectious disease is transmitted from one host to another.

d
Lt
Viruses
Viruses are very small pathogens that cannot reproduce or survive
without a host. They can infect many different types of living things.

te
P
on
Measles

ti
Rhinovirus virus Retrace our steps

The common cold is a disease Measles is a disease What are some

ca
caused by the rhinovirus. caused by the measles virus. symptoms of the
common cold and
Fungi measles? How do
du

Fungi are living things like mushrooms, yeast and moulds. these diseases
transmit?
Some of them can cause diseases in animals and plants.
E

Spores
n
to
ls

Fungus that causes Athlete's foot Fungal spores that cause histoplasmosis
A

Athlete's foot is an infection that is caused by Histoplasmosis is an infection caused by fungal

a type of fungus that usually grows on our skin spores usually found in bird droppings. A person
on the feet. It can also grow on hair and nails. can be infected by inhaling these spores and may
This infection can spread to another person in develop fevers and coughs.
)

wet environments like the pool.

(c

Transmit – To pass something from one living thing to another or one place to another
Host - A larger living thing that usually provides nutrients and shelter to a smaller living thing
Clues
such as pathogens
Spores - Small particles from fungus that allow the fungus to reproduce

38 Chapter 3
 Bacteria
Bacteria are very small living things commonly found in many places. Not all
bacteria are harmful. Only some types of bacteria can cause infections.

d
Lt
Bacteria are so small that
we cannot see them with
our eyes! We can use a

te
microscope to see them.

P
on
Tuberculosis is a
disease caused by
a type of bacteria

ti
that usually
affects the lungs.
The bacteria can
ca
spread between
humans through How are the respiratory system of mammals,
the air. birds and reptiles similar to ours?
du

Cholera is a disease
caused by bacteria
usually found in
E

contaminated food
and water. A person
can be infected with
n

these bacteria when

consuming food
and water that are
to

contaminated with
human faeces.
ls

Watch out!
A

Not all bacteria are bad for us.

Some good bacteria can be found in our digestive system. They help us to
)

digest food and produce vitamins in our body. Some of them even protect
us against other harmful bacteria and keep us healthy. We can find good
(c

bacteria in yoghurts, cheese and fermented food such as kimchi. We eat

them so that there is a community of good bacteria in our body! Let’s learn
more about bacteria by watching this video.

Pathogens and Diseases 39

 Red blood cell

d
Lt
Parasites
Parasites are living things
that live on or in a host.

te
They depend on the
host for nutrients. They

P
can also cause harm to
Malaria parasite
the host.

on
Malaria is a disease caused by a parasite that infects a type
of mosquito. When the infected mosquito bites a human, the
malaria parasite is transmitted from the mosquito to the human.

ti We should always
ca
Toxoplasmosis parasite make sure that the raw
meat is fully cooked
before we eat it!
du
E
n
to

Toxoplasmosis is a disease caused by a parasite

commonly found on raw or undercooked meat. If we
ls

eat uncooked meat, this parasite can be transmitted

to our body.
A
)

Pathogens can be found everywhere. They are found in the air we breathe, in the
(c

food we eat and on the surfaces of objects including the surfaces of our bodies.
Pathogens can even be found in our eyes, nose and digestive system!

40 Chapter 3
 Solve this!

Match each disease to the correct pathogen that causes it.

Athlete’s foot Parasite

d
Malaria Bacteria

Lt
Measles Virus

te
Tuberculosis Fungus

P
How do we control the spread of diseases?

on
Pathogens can spread from one person to another through
different ways. We call the spreading of pathogens transmission.

Through the air

ti
Some pathogens can be transmitted through the air. When an
ca
infected person talks, coughs or sneezes, tiny droplets can be
released into the air. These droplets contain pathogens. When
Pathogens in
another person breathes in or comes into contact with these
du

droplets
droplets, they may become infected too.

2 Let ’s investigate!
E

sion of infectious diseases

Aim: To find out how distance affects the transmis
n

through the air.

to

Materials:
Spray bottle containing water   Measuring tape
ls

Instructions:
A

1 Get into pairs. Stand 20 cm away from your classmate.

2 Your classmate will hold the spray bottle and spray water droplets in your
)

direction. The sprayed water represents the water droplets produced when
(c

a person talks, coughs or sneezes.

3 Observe if there are any water droplets that land on you.

4 Move 20 cm further away from your classmate and repeat Steps 2 and 3.
kboo
k

5 Repeat Step 4 and record your observations in the table. Worksheet 1

or
W

Pathogens and Diseases 41

 Distance from your classmate (cm) Are there droplets on you? Tick (✓).

20

40

d
60

Lt
80

100

120

te
140

160

P
180

200

on
Questions:
1 What pattern do you observe from your results?

ti
________________________________________________________________
ca
2 What can you infer about the distance between us and an infected person,
and the transmission of infectious diseases through droplets?
________________________________________________________________
du

________________________________________________________________
3 From this experiment, what do you think can protect us from an infectious
E

disease that transmits through droplets in the air?

________________________________________________________________
n
to

These are some ways in which we can reduce the transmission of pathogens
through the air.
ls

We can keep a safe

A

distance between us
and other people.
2 metres
)
(c

We can wear a face mask and keep a distance away from people who show symptoms of the infection.

42 Chapter 3
 Retrace our steps

How do we reduce
the transmission of

d
infectious diseases
with vaccines?

Lt
When we cough or sneeze, We can also reduce
we should cover our mouth transmission by getting Do all pathogens

te
and nose with a tissue or vaccinated. spread through
handkerchief. the air?

P
Through physical contact
Pathogens can be transmitted from one person to

on
another through physical contact with faeces or
body fluids such as saliva, blood or urine.

Think-Pair-Share

ti
ca
Mix some oil and flour together. Apply the mixture of oil and flour on your hands. The oil and
flour represent the pathogens on your hands. What happens if we touch the things around us
with our hands?
du

What is the best way to wash our hands so that we can remove the oil and flour completely? Is
this way effective to stop infectious diseases from spreading?
E

We can reduce or stop the transmission of diseases by

practising good hygiene habits. Handwashing is one of the best
n

ways to stop the spreading of diseases. We can do this properly

with soap and water. Let’s learn how to wash our hands by
to

watching this video!

ls
A
)
(c

We should wash our hands We should also wash our We should avoid touching
before preparing or eating food. hands after handling animals or our faces with unwashed
playing outside. or dirty hands.

Pathogens and Diseases 43

 Through food and water
Pathogens can also be transmitted through contaminated food and water.

d
Lt
te
P
on
We should always wash our fruits We should dispose our rubbish
and vegetables before eating them. in a safe and proper manner.

ti
ca
du
E
n

We can treat our water so that We should store our food properly so
they are clean and safe for drinking. that they are not easily contaminated.
to

By insect vectors
ls

Pathogens can also be transmitted by insects. An insect that carries and

transmits a pathogen to another living thing is called an insect vector.
A

Mosquitoes and flies are examples of insect vectors. When a mosquito that is
infected with the malaria parasite bites a human, the malaria pathogen enters
the human's blood, causing the human to be infected with malaria.
)
(c

Think-Pair-Share

Using the Internet or books, research some ways to reduce the chances of being bitten by
mosquitoes. Create a poster and share with the class.

44 Chapter 3
 To lower the risk of being infected with malaria, we can find ways to avoid
getting bitten by mosquitoes.

d
Lt
te
P
We can apply insect repellent on ourselves when we are outdoors.

on
ti
Mosquito net
ca
du
E

We can sleep in an air-conditioned room We can also sleep under a mosquito

n

with the doors and windows closed. net treated with insecticide.
to

Mosquitoes can breed in clean and

ls

stagnant water. We should check

A

frequently for stagnant water in our

surroundings and remove them
to reduce the chance of mosquito
)

breeding. We can also use insecticides

(c

to kill mosquitoes.

Breed - To produce young

Clues Stagnant water – Water that is not flowing

Pathogens and Diseases 45

 Science in context
Not all information available on the
Internet are accurate! It is important
Coronavirus disease (COVID-19) is an to make sure that you are obtaining
infectious disease caused by a new type and sharing information from

d
of coronavirus. An infected person may reliable websites.
show symptoms such as fever and cough.

Lt
The COVID-19 virus spreads mainly through
saliva or droplets in the air when an infected
person coughs or sneezes. What are some

te
ways to prevent the spread of the COVID-19
virus? Research and discuss with your

P
classmates.

on
Solve this!

The following scenarios show how infectious diseases can be transmitted.

ti
For each scenario, write down the correct way to control the spread of
ca
the disease.
du
E
n
to

_____________________________ _____________________________
ls
A
)
(c

_____________________________ _____________________________
kboo
k
or
Worksheet 1
W

46 Chapter 3
 What are our body’s defence mechanisms against diseases?
Harmful pathogens that enter our body can cause Mucus is a sticky
infections. As such, our body has defence mechanisms substance produced
by some of our body

d
to prevent us from falling ill easily or frequently. These parts, such as the
defence mechanisms include our skin. Our body

Lt
mouth and nose!
also produces secretions such as stomach acid and
mucus. This is another way the body protects us
from infections.

te
Think-Pair-Share

You will need the following materials — salt, plastic cling wrap, vinegar and glue. The salt represents

P
disease-causing pathogens, the remaining three items represent the defence mechanisms of our
body. The plastic cling wrap represents our skin, the vinegar represents stomach acid while the
glue represents mucus. Observe what happens when these items come into contact with salt.

on
Questions:
1 H ow do you think the plastic cling wrap, vinegar and glue model our body's defence
mechanisms?

ti
2 H ow well do these models represent the different functions of our body?
3 W hat are some questions you can ask in your scientific enquiry to find out how our defence
ca
mechanisms work?
4 Can you carry out tests in real life to find out how our defence mechanisms work?

Why or why not?

du

Skin
Other than protecting us from the heat or cold and giving us the sense of
E

touch, the skin is also a physical barrier. It is one of our body's first lines of
defence to prevent pathogens from entering our body. If the skin is broken
n

through cuts and wounds, the body loses its protective barrier and pathogens
can enter the body easily.
to

I have a cut on We should clean your

ls

my knee! wound to reduce the

risk of infection!
A
)
(c

Defence mechanism - A function or reaction to protect from harm or infection

Clues Secretion - Substance produced or released by organs in the body to carry out certain
functions

Pathogens and Diseases 47

 Stomach acid
The stomach secretes acid which helps us to digest food.
It also protects us from pathogens. If the food or water we
consume contains pathogens such as harmful bacteria,

d
stomach acid can kill these pathogens.

Lt
Mucus
Mucus is a sticky substance secreted by our body.

te
If we have a cold or an allergic reaction, more mucus Mucus trapping
pathogens
is produced in our throat, nose and mouth to trap
pathogens and unknown substances. The trapped

P
pathogens can make us cough or sneeze, allowing us to
blow the pathogens out of our body together with the

on
mucus. Mucus can also help to kill some pathogens.
Together with good hygiene habits, our body's defence

ti
mechanisms work to protect us from infectious diseases.
ca
Science in context
du

How do healthcare workers diagnose and treat malaria

patients? Watch this video to find out more.
E
n

Solve this!

Match each defence mechanism with its correct function.

to

Skin Kills pathogens found

ls

in food or water
A

Prevents pathogens
Stomach acid
from entering body
)
(c

Traps pathogens
Mucus
and kills them
kboo
k
or
Worksheet 2
W

48 Chapter 3
 Crack the case

Infectious diseases
are caused by

d
can spread through

Lt
Physical contact Food and water
Pathogens
with saliva,

te
___________ ,
1. ___________ ___________ or

P
___________
2. ___________ Insect
vectors

on
3. ___________ Air
4. ___________

ti
ca
We can reduce the transmission by:
 Can be killed by
Storing our food properly
_________________
du

Washing our hands with _________________

 Can be trapped and
killed by ___________  Applying _________________ on ourselves
e
 Can be blocked by th when going outdoors
E

___________ which is _________________ when we sneeze or cough

one of our body's first
lines of defence
n
to

(🗸).
What should Tim do? Tick
ls

.
ld m ee t Ad a an d ha ng out in her room for a while
Tim shou
A

close
d Ad a shou ld wear face masks and avoid standing
Tim an
meet.
to each other when they
)

od to share with Ada.

Tim should bring some fo
(c

ect re pe llent on him se lf before visiting Ada.

Tim should apply ins

kboo
k
or
Consolidation worksheet
W

Pathogens and Diseases 49

 CHAPTER 4 Physical Changes

d
Lt
Oh no! What should we do now?
Our gowns are wet! We cannot
go to the ball in wet gowns! There
is not much time left!

te
P
on
ti
ca
du

What can I do to help

Ada and Vera solve
their problem in the
shortest time?
E
n
to

What Will I Learn

✓ Describe the temperature at
which a substance changes
ls

state as a property of the sub

stance.
✓ State some properties of gases
.
A

✓ Identify physical changes tha

t are reversible and describe
them.
✓
)

Describe how boiling and eva

poration are different.
(c

Is the water causing What process can

a physical change or reverse the change?
chemical change to What factor can help
the girls' gowns? Is the to
speed up the process
change reversible? to
reverse the change?
50 Chapter 4
 What are physical changes? Retrace our steps

A physical change can be a change in shape. What are some

physical changes

d
you know?

Lt
te
Crushing a piece of paper or tin can may change its shape

A change in state is also a type of physical change.

P
on
ti
ca
du

Ice melts to form water Water boils to form hot water vapour

Physical changes do not produce new substances. Most physical

E

changes can be easily reversed. They can be returned to their original

form. We say these changes are reversible.
n

However, there are exceptions. Some physical changes cannot be

easily reversed.
to

Physical changes that are reversible

ls

Think-Pair-Share

You will be given a piece of paper. What can you do to the paper to cause a physical
A

change to it? How can you reverse this physical change?

Paper can be folded, rolled or crumpled up into a

)

ball. We can unfold a folded or crumpled-up paper

(c

and flatten it to return it to its original form. Hence,

these changes are reversible.

Physical Changes 51
 Let’s investigate!
1
ge
ther adding water to sand is a physical chan
Aim: To find out whe
that can be reversed.

d
Lt
Materials:
 Container of dry sand
 Water

te
Instructions:

P
1 Touch and feel the dry sand.

Can you easily shape the sand and make a sandcastle with it? _______

on
2 Add some water to the sand and feel the sand again. How is the sand

different from the dry sand in Step 1?

Now, can you easily shape the sand and make a sandcastle with it? _______

ti
3 Place the wet sand to dry under the Sun for a few days. Touch and feel the

sand after a few days.

ca
Does it feel like the dry sand in Step 1? _______
Can you easily shape the sand and make a sandcastle with it? _______
du

Questions:
1 Was a new substance formed when water was added to sand? _______
E

2 Describe the physical property that was changed when water was added to

the sand.
n

3 Does adding water to sand result in a physical or a chemical change?

to

4 What did you observe in Step 3? Is this change reversible? Explain.

ls
A
)
(c

52 Chapter 4
 Adding water to sand is a physical change. It changes the texture of the sand.
Wet sand feels stickier and can be moulded easily. Dry sand cannot hold its
shape and cannot be moulded easily.

d
Lt
te
P
on
ti
We can use wet sand to build sandcastles.
ca
When we add water to sand, a wet sand mixture is formed. Water does not
react with sand and no new substances are formed. This is a physical change.
du

This physical change can be reversed by allowing water in the wet sand
E

to evaporate.
n

Physical changes that are not easily reversible

to

Think-Pair-Share

Is breaking a glass bottle or tearing up a piece of paper a physical or a chemical change?

ls

Maybe we can stick

A

them back together

with tape…
)
(c

Physical Changes 53
 These eggs are
not to be cooked! Oh no! I cannot
When a glass bottle is broken, the broken I wanted to hatch put them back
pieces are still glass. The substance that them into chicks! together.
makes up the glass bottle has not changed.
No new substances are formed during

d
the process.

Lt
So, breaking a piece of glass or tearing up
a piece of paper only changes the shape of
the substance. Although they are physical

te
changes, they are not easily reversed.
Cracking an egg, cutting our hair and

P
trimming our fingernails are other examples
of physical changes that cannot be easily reversed.

on
kboo
k
or
Worksheet 1
Solve this!

W
ti
Some physical changes are shown below. Tick (🗸) the physical changes that
are easy to reverse.
ca
du

Melting ice Chopping wood Boiling water

E
n
to

Adding water to sand Mixing red and green marbles Shredding paper
ls

What are some physical properties of substances? Retrace our steps

A

A substance has physical properties such as mass and What are some
the temperature at which it changes state. properties of
)

solids, liquids
and gases?
(c

Mass as a property of a substance

Scientists use physical properties to observe and measure substances.
These properties include mass. We can measure the mass of different matters.
Solids and liquids have mass. What about gases like air?

54 Chapter 4
 Watch out!

Does air have mass?

What do you
think will happen
if we deflate the

d
red balloon on
the left?

Lt
Watch this video to
see this experiment
in action!

te
When we deflate the red balloon, air is released
from it. As the amount of air in the red balloon

P
decreases, the red balloon moves up and the
blue balloon moves down. This shows that the
inflated blue balloon containing more air has

on
a greater mass than the deflated red balloon
containing less air.
This observation shows that like solids and
liquids, gases such as air have mass too.

ti
ca
Temperature at which a substance changes state as a property of a substance
du

Let’s investigate!
2
uid using the shortest
E

ter from solid to liq

e of wa
Aim: To change the stat
amount of time.
n

Use a thermometer
to

Materials: to find out the

temperature of the ice
Ice cubes Clothes  Candle and tripod cubes during melting.
Warm water Torch stand with wire gauze
ls

Does the temperature

change as the
Thermometer Beaker Stopwatch
ice cubes melt?
A

Magnifying glass

Instructions:
)

1 Choose the equipment from the list to melt your ice cubes.
(c

Plan how you can melt all the ice cubes given using the
shortest amount of time.
2 In your plan, include a step to measure the temperature of
the ice cubes when they are melting.
Physical Changes 55
 3 Draw the set-up of your experiment in the space below.
Record the time taken for your ice cubes to melt completely.

d
Lt
te
P
on
ti
ca
Time taken for ice cubes to melt completely: __________________________

Question:
du

Discuss your results with your classmates. Which set-up melted the ice cubes
the fastest? Why? ___________________________________________________
E

Conclusion:
The ice cubes that melted the fastest were provided with the ______________
n

heat. But all the ice cubes melted at the same temperature at _______ºC.
This is known as the ______________ point of ice. During melting, the
to

temperature measured remains ______________.

ls

Melting point and freezing point as a property of a substance

A

When we apply heat to a substance or its surroundings, we are increasing

its temperature.
)
(c

When the temperature of the substance reaches its melting point, the
substance starts to melt and changes from solid to liquid. During melting, the
temperature of the substance does not change. It remains at its melting point
until all of the solid has turned into liquid.

56 Chapter 4
 Ice cubes start to melt when During melting, the
the temperature reaches the temperature of ice cubes
melting point of water (0 ºC). remains at 0 ºC.

d
Heat from the candle

Lt
increases the temperature
of the ice cubes and its
surroundings.

Ice cubes are melting

te
P
All the ice cubes have Temperature starts to
melted completely. increase only when all the
ice cubes have melted to

on
become a liquid.
After all the ice cubes have melted,
heat from the candle continues to

ti
increase the temperature of the
water and its surroundings.
ca
All ice cubes have melted
Think-Pair-Share
du

Freeze a beaker of water. Measure the temperature of the water as it freezes.

What do you notice about the temperature of the freezing water?
E

When we cool a substance or the surroundings of a substance, we remove

heat from it. The temperature of the substance and its surroundings drops.
n

When the temperature of the substance reaches its freezing point, the
to

substance starts to solidify and changes from liquid to solid. During the
process of solidifying or freezing, the temperature of the substance does not
ls

change. It remains at its freezing point until all of the liquid has turned into solid.

When water is solidifying,

A

the temperature of the

water remains at 0 °C.
)
(c

Place the bowl of

water in the freezer
Water at 30 ºC
Water freezing in the freezer

Physical Changes 57
 Boiling point as a property of a substance
Think-Pair-Share

Boil a beaker of water. Measure the temperature of the water as it boils.

What do you notice about the temperature of the boiling water?

d
Lt
If the temperature of a substance reaches its boiling point, the substance
starts to boil and changes from liquid to gas. During boiling, the temperature of
the substance does not change. The temperature of the substance remains at

te
its boiling point until all of the liquid has turned into gas.

P
Water starts to During boiling, the
boil when the temperature of water
temperature of
remains at 100 ºC.

on
the water reaches
its boiling point
(100 ºC).

ti
ca
Water boiling

If the temperature of a gas drops until it reaches its boiling point, the gas starts
to turn into liquid. This is known as condensation. Similarly, the temperature of
du

the gas does not change until all of the gas has turned into liquid.
E

Water
Water boils and condensing When the hot water
changes from liquid vapour touches the cold
mirror, it cools and loses heat.
n

to hot water vapour.

Water vapour is If the temperature of the
hot water vapour drops till it
to

water in gaseous
state. reaches the boiling point of
water, the hot water vapour
changes into water.
ls
A

What are the

other properties of We can tell by
)

gases? How do we tell feeling and observing the

effects of these substances.
(c

that gases are present

around us? What do you feel when you
stand in front of a turning
fan? Can you feel the air
resistance?

58 Chapter 4
 Solve this!

The melting point of Substance Z is 20 ºC. Its boiling point is 80 ºC.

d
1 If Substance Z is removed from a place of 10 ºC and placed in a room

with a temperature of 25 ºC, what will happen to it?

Lt
2 If we heat Substance Z from 25 ºC to 80 ºC, what will happen to it?

Do all substances change state at the same temperature?

te
Think-Pair-Share

P
Liquids such as water, oil, vinegar, soda and juice look, smell and feel different. What about
their melting points and boiling points? How do the melting and boiling points of these
substances differ? Discuss with your classmates how you plan to find out.

on
My water is a My chocolate

ti
liquid at this is a solid at this
temperature. temperature.
ca
du

The states of these

substances depend
What about on the temperature
oxygen in the air they are in. The
that we breathe?
E

temperature is now
25 ºC.
n
to
ls
A

Think-Pair-Share

Using a thermometer, measure the temperature of the different corners of your classroom.
Compare the temperature measured with that of your classmates'.
)

Is there a big difference in the temperature in the different parts of the room?
(c

Room temperature is a range of temperature that is comfortable for us to

remain in. It can vary in different parts of the world. In science, we usually say
that room temperature is 25 ºC.
Physical Changes 59
 Different substances have different melting points and boiling points. This
physical property is unique to each substance. So, scientists can use this
property to identify an unknown substance.

d
For example, when an unknown substance is given to us, if we measure and
find that the melting point of the substance is 0 ºC and the boiling point of the

Lt
same substance is 100 ºC, we can identify the substance as pure water.

te
Oxygen, hydrogen,

P
carbon dioxide, nitrogen and
helium are gases at room
temperature. Some of these

on
gases can be used to inflate
my balloons!

ti
ca
Do you think pure water
du

and salt water change

states at different
temperatures?
Different substances
E

change states at different

temperatures.
n
to
ls

Hence, in a
place where the conditions
such as the surrounding
A

temperature are the same,

we can find substances in
different states.
)
(c

60 Chapter 4
 When the melting point of a substance is higher than room temperature
(25 ºC), it appears as a solid at room temperature.

d
Lt
te
Most metals are solids at room temperature Plastic is a solid at room temperature too.
as they have very high melting points.

P
If the freezing point of a substance is lower than room temperature, it appears

on
as a liquid at room temperature.

ti
ca
du
E

Water is a liquid at room Chocolate melts on our Mercury is the only metal that
temperature as its freezing hands as it has a melting is a liquid at room temperature.
point of 0 ºC is lower than point lower than our body
room temperature (25 ºC). temperature of around 37 ºC.
n
to

If the boiling point of a substance is higher than room temperature, it appears

as a liquid at room temperature. Water is a liquid at room temperature.
If the boiling point of a substance is lower than room temperature, it appears
ls

as a gas at room temperature. Oxygen has a boiling point of -183 ºC. It is a gas
A

at room temperature.

Solve this!
)
(c

Vera found a beaker of liquid in the science laboratory. She wants to identify
the liquid in the beaker. She thinks that the liquid is water. What can Vera do to
confirm if the liquid in the beaker is water?
kboo
k
or
Worksheet 2
W

Physical Changes 61
 Can we use physical properties to identify changes in states?

Boiling and evaporation are both physical processes where matters change
states from liquid to gas. How do we know if the physical process occurring is
boiling or evaporation? Let us compare what happens to substances when

d
they undergo boiling and evaporation.

Lt
Boiling Watch out!

Think-Pair-Share We can sometimes see mist rising from a cup of hot

te
Boil some water. Observe. tea. We also see similar mist when we boil water.
What happens when water Can we tell if something is boiling or evaporating
reaches its boiling point? based on the observation of mist above a liquid?

P
Boiling occurs at a fixed temperature called the boiling point. When

on
a liquid boils, we can see bubbles forming throughout the liquid as
the liquid changes into gas. The bubbles formed are the substance in
gaseous state.

ti
Energy is needed to heat a liquid to its boiling point. We can use heat
sources such as a heating plate, stove or fire.
ca
du

How do I know
if the water is
boiling?
E

During boiling, water

turns into gas and rises
n

to the water surface

and escapes into the
to

Mist
surrounding air as
hot water vapour. Hot
ls

water vapour is also

known as steam. When
A

the hot water vapour

loses heat to the cool
surrounding air, it
)

condenses to form tiny

(c

Gas particles
inside a bubble water droplets. This is
Liquid particles the mist that we see.
of water

62 Chapter 4
 Evaporation
Evaporation is the process where liquid
changes into gas. But this change in state

d
Gas particles
happens only at the surface of the liquid. of water
vapour

Lt
When the liquid is exposed to warmer
surroundings, some liquid particles at the
surface gain enough energy to escape

te
from the surface of the liquid. When this Liquid particles
happens, water changes from liquid to of water

P
gas. Evaporation can happen at any
temperature below the boiling point.

on
ti
ca
du

The puddle of water

E

will disappear after

some time as water
evaporates.
n

During evaporation,
we can also observe mist We can hang our
wet clothes here!
to

rising from the liquid. The mist

is the water vapour that has They will dry as water
condensed to form water evaporates from
droplets in the air. them.
ls
A

mist We can see that in both boiling and evaporation, the

liquid changes into a gas. However, boiling occurs
)

throughout the liquid while evaporation occurs on

(c

the surface of the liquid. Boiling only occurs at the

boiling point of the substance while evaporation can
occur at any temperature below the boiling point.

Physical Changes 63
 Let’s investigate!
3
that
To plan an ex perimen t to find out the factors
Aim:
ation.
affect the rate of evapor

d
Lt
Materials:
 Trays of different sizes Weighing scale
 Beakers of different sizes  Containers with lids

te
 Stopwatch Table fan
Bunsen burner  Ruler

P
 Water  Candle
 Thermometer  Moisture absorber

on
Instructions:
1 Plan an experiment to find out the factors that affect the rate of evaporation.

ti
2 Use the following template to help you plan your experiment.
ca
Factor to test for: Temperature / Wind / Humidity / Surface area
du

Independent variable: _________________________________________

Dependent variable: _________________________________________

E

Constant variables: _________________________________________

n

Experimental set-up:
to
ls
A
)
(c

Steps:
__________________________________________________________________

__________________________________________________________________

64 Chapter 4
 3 Record your results in a table.
4 What can you conclude from your results?
________________________________________________________________

d
Lt
The temperature of the surroundings, the amount of wind, humidity of the
surroundings and surface area exposed affect the rate of evaporation.

Wet clothes dry faster on a hot day as the

te
temperature of the surroundings is high.

P
By spreading out and
hanging our clothes, we increase the
surface area of the wet clothes exposed

on
to the surroundings. There is more
surface area for evaporation to take
place. This way, the clothes will take a
shorter time to dry.

ti
A hot day

The clothes will dry even faster on a

ca
hot and windy day.
du

Humidity refers to the

amount of water vapour in the air.
Our clothes can dry faster in a dry
E

and less humid environment with

less water vapour in the air.
n

A hot and windy day

to

Solve this!

1 What is happening to the water shown in the photo

ls

on the right?
___________________________________________
A

2 Which observation tells you so?

___________________________________________
)

3 What is the temperature of water shown in the photo? ________

(c

4 The pot of water is then placed on a table. After a while, the amount of

water decreases in the pot. What factors affect how fast this happens?
_______________________________________________________________
kboo
k
or
Worksheet 3
W

Physical Changes 65
 Crack the case

has Matter

d
Physical properties

Lt
such as

te
___________at
___________
which a substance

P
of a
changes states
substance

on
ti
ca
Freezing or
solidifying Melting
du

Occurs at ___________ or
E

Liquid Solid Solid Liquid

___________ point (0 ºC)
n
to

st
use to he lp th e girls dry their gowns in the shorte
ls

Which item can Cyru s

time? Tick (🗸). d hottest mode and blow
wi nd sp eed an
A

hig he st
Set the hair dryer to its
it on the gowns.
highe st wind sp ee d an d place the gowns near
Turn the table fan on its
)

the fan.
(c

e go wns with the pa pe r fan as quickly as possible.

Fan th
s with all his m ight using his mouth and lungs.
Blow at the gown

66 Chapter 4
 undergoes
Physical Changes

d
Lt
Can be reversible or not easily reversible

te
such as

Changes in Changes in
Changes in shape,

P
states mixtures
colour or texture

on
Occurs at any temperatu
re

ti
Occurs at a specific below boiling point
temperature
ca
du

Boiling Condensing
E

Occurs at
n

Gas Liquid
___________
to

point (100 ºC)

ls

Evaporating
A

Liquid Gas

Occurs at the
)

___________ of the
(c

Occurs throughout
liquid
the liquid

kboo
k
or
Consolidation worksheet
W

Physical Changes 67
 CHAPTER 5 Heat and Electricity

Why are my lamps so

d
dim while yours are
brightly lit? Are my lamps

Lt
not working?
It cannot be, Ada.
We bought the
same lamps!

te
P
on
ti
When I touch
these toys, the metal
toys in the doll's house
ca
feel warmer than the
plastic and wooden
toys!
du
E
n
to

Ada and Vera are putting tog

ether their dolls' houses.
To light up the rooms, they co
nnect two lamps to a cell.
What can Ada do to make he
r lamps shine brighter?
How are the circuits
ls

connected in the
dolls' houses?
A

What Will I Learn

How does electricity
Create, represent and compare circuits using diagrams flow differently from the
and
)

conventional symbols. battery to each lamp in the

(c

Compare the brightness of lamps in series and para

llel circuits.
two different circuits?
Describe electrical conductivity and thermal conductiv
ity as How do the to
properties of a substance. y
parts gain hea
t in
the dolls' house
s?
68 Chapter 5
 Retrace our steps
How does heat energy get transferred?
If you leave a cup of
When a substance gains heat, energy warm water on the
from the surroundings is transferred to it. table, what happens
to the temperature of

d
Similarly, when a substance loses heat,
the water after a while?
energy from the substance is transferred

Lt
Describe the energy
to its surroundings. transfer.

Let’s investigate!
1

te
slow down the melting of ice cubes using the right materials.
Aim: To

P
Materials:
 Materials such as newspaper, aluminium foil, plastic sheet, bubble

on
wrap and fabric
 Ice cubes   Weighing scale   Rubber bands
Instructions:
ti
1 Measure and record the mass of each ice cube.
ca
2 Wrap each ice cube with one of the materials. Use a rubber band to

secure it. Leave one ice cube unwrapped as a control.

du

3 When the control ice cube has melted, unwrap all the ice cubes.

4 Measure the mass of each ice cube and record it in a table.

E

5 Calculate the mass lost as ice that has melted and record it in your table.

6 Which material is the best in slowing down the melting of ice cubes?
n

Rank the materials from the best to the worst.

Conclusion:
to

When an ice cube is taken out of the freezer, _________ from the
surroundings will be transferred to the ice, causing the ice to _________.
ls

When the ice cube is wrapped by a material, heat from the surroundings
transfers to the ( material / ice cube ) first, before reaching the ( material /
A

ice cube ). So, the transfer of heat to the ice cube slows down. The ice cube
does not ( gain / lose ) heat as fast and therefore melts slower. We call this
)

material a thermal ( conductor / insulator ).

(c

Think-Pair-Share

Which materials from Let’s Investigate 1 do you think can keep a bowl of hot food hot
for a longer period of time?

Heat and Electricity 69

 Thermal conductors and insulators

Materials are made up of different substances. Different substances allow heat

to pass through quickly or slowly.
Substances such as metals allow heat to transfer quickly. We say that they can

d
conduct heat well and are good thermal conductors.

Lt
Two panes of glass

Space
filled with

te
air or a
type of
gas

P
Which spoon should

on
I use to stir the food
Air is a good thermal with?
Double-glazed insulator. It is used between
windows two panes of glass within

ti
double-glazed windows. This
will reduce heat transfer into The knob
and out of the house.
ca
on the pot lid
is made of an
Wood insulator such
Metal
as plastic, wood
du

or rubber so
that the person
holding it will
not get burnt.
E

Bubble wrap has

n

air trapped inside. Air is a

good thermal insulator. It can
to

keep my hot food warm and

Metal is a
cold food cool!
good thermal
conductor.
ls
A

Thermal insulators A cooking pot is made of

)

slow down the metal. Metals are good thermal

(c

transfer of heat from conductors so the pot can heat

the hot object to its Thermal insulators slow down the transfer up quickly. Heat energy applied
surroundings. So, the of heat from the surroundings to the to the cooking pot will transfer
hot object does not cold object. So, objects placed inside the through the metal quickly. If we
lose heat quickly and insulator do not gain heat quickly and can touch the metal part of the pot,
remains warm longer. remain cold for a longer period of time. we may get burnt.

70 Chapter 5
 Some substances do not allow heat to transfer quickly. They are poor thermal
conductors or thermal insulators. Non-metals such as wood are usually
thermal insulators.

d
Lt
te
Notice that heat
I wear gloves always flows from a hotter area to a
before I take the tray of colder area. Heat flows from an object

P
bread out from the oven. of higher temperature to an object
Oven gloves are made of lower temperature. We can also
of thermal insulators like describe it as heat being gained or lost.

on
fabric. Fabric can trap Heat is the flow of thermal energy
air and air is also a good from one object to another.
Although
thermal insulator. diamonds are

ti
non-metal,
they are unique
as they are
ca
good thermal
conductors.
We can use this
du

property to test
if a diamond is
real.
E
n
to
ls

Fabric
A

How can we
tell if this door
knob is made of
)

diamond?
(c

Think-Pair-Share

Hot water is placed in a metal cup and a plastic cup. After 15 minutes, which cup of water will be
cooler? Why?

Heat and Electricity 71

 Let’s investigate!
2
al
erm al energy is transferred through a therm
Aim: To model how th
al insulator.
conductor and a therm

d
How fast should I That is so slow,

Lt
pass the ball to the Cyrus!
next person?

Why do you

te
think Cyrus is
passing the
ball so slowly

P
to Tim?

on
Form groups of six and stand close to one another.

ti
1

2 One person will role-play a good thermal conductor. Another person will
ca
role-play a thermal insulator.
3 You will be given some balls. Pass the balls down the row from one person
du

to the next.
4 The balls represent thermal energy and the passing of the balls from one

person to the next represents the transfer of thermal energy.

E

Think-Pair-Share
n

During winter, we wear thick coats and puffy jackets to keep us warm. What are the coats
made of? Are the materials thermal conductors or insulators? Do they contain trapped air in
between the layers? Discuss how they keep us warm in the cold weather.
to

Thermal conductivity of a substance is the ability of the substance to conduct

ls

heat. It is a physical property of the substance.

A

kboo
k
Solve this! or
Worksheet 1
W

Which of the following are good thermal conductors? Circle.

)
(c

Woollen yarn Diamond Steel plate Silver spoon Plastic bottle

72 Chapter 5
 Retrace our steps

How does electricity pass through a circuit? What electrical

components are
needed to construct
a circuit to light up
Let’s investigate!
3 a lamp? What will

d
happen if there is a
ts using different break in the circuit?

Lt
Aim: To construct circui
mpare circuits drawn.
components and to co How many different
circuits can we make
with the same set of

te
Materials:
equipment?

P
Buzzer
Wires Motor

on
Cells Switch Lamps

Instructions:

different circuits. ti
1 Using the materials provided, construct two What precautions do we
need to take when handling
ca
electricity? How can we stay
safe when building circuits?
2 Draw the circuits that you have constructed below.
du
E
n
to
ls

3 Find a friend who has constructed the same circuit as you. Compare your
A

drawing with your friend’s. Did both of you draw each component in the
same way? Is it easy to identify the components in your friend’s drawing?
)

Question:
(c

How should we draw our electrical components so that the components can
be easily and correctly identified? ______________________________________
___________________________________________________________________
Heat and Electricity 73
 Electric circuit diagrams are used by everyone from all over the world. To
make sure that anyone in the world can understand the circuit drawn, we use
conventional symbols to represent the components.
Conventional symbols

d
are used everywhere in
the world so that everyone

Lt
Cell Motor
can recognise them. This
symbol represents a
junction of conductors.

te
Battery Open switch

When two or more

cells are connected

P
together, what do
they form? Lamp Closed switch

on
Wire

ti
Buzzer
ca
Conventional symbols to represent circuit components
du

Using these symbols, we can draw circuit diagrams to represent electrical

circuits.
E

What if there is more than

Cell one lamp in a circuit? What
Cell
are the different ways
n

we can arrange them in

a circuit?
to

Wire
Wire
Lamp
ls

Switch Lamp
A

Switch
)

Simple circuit diagram

(c

A circuit consisting of a lamp, a cell and a switch connected

by wires can be represented in a simple circuit diagram.

Clues Conventional – Following a standard way in which something is commonly done

74 Chapter 5
 How does the arrangement of components in a circuit affect the
brightness of a lamp?

Circuits can be connected in different ways. There are two types of circuits —

d
series circuits and parallel circuits.

Lt
In a series circuit, components are connected side by side. There is only one
complete loop. So, electricity flows through a single path.

te
P
There is only
one path for
me to run on!

on
ti
ca
Both lamps share the energy
that flows through the circuit.
du

In a parallel circuit, components are connected in branches. There is more

than one complete loop. Electricity flows through more than one path.
E

I am at a
junction now! There
n

are two paths for me

to choose from!
to

I can choose
the first path!
ls
A
)

I can choose
(c

the second
path!
The lamps are arranged in two Path 1
different loops. Path 2

Heat and Electricity 75

 Retrace our steps
Let’s investigate!
4 In a series circuit,

uc t a se ries circuit and a parallel circuit what happens to the

Aim: To cons tr brightness of the
ight ne ss of the lamps in both

d
and co m pare the br lamp when more
components are
circuits.

Lt
added to the circuit?
Why?
Materials:
Wires Two switches

te
Six lamps Two cells

P
Instructions:
1 Construct the circuits shown in these circuit diagrams:

on
ti
ca
du

2 Predict which lamps will be brighter when we close the switch. Circle.
I predict the lamps in the ( series / parallel ) circuit will be brighter.
E

3 Close the switch. Observe the brightness of the lamps in both circuits. Circle.
n

The lamps in the ( series / parallel ) circuit are brighter.

to

4 Add one more lamp to each circuit. What happens to the brightness of
the lamps?
ls

Series circuit: All the lamps have ___________________________________

Parallel circuit: All the lamps have __________________________________
A

Questions:
)

1 How many complete loops does each circuit have?

(c

________________________________________________________________
2 In which circuit are the lamps brighter? Circle. ( Series / Parallel ) circuit
3 Is your prediction correct? Circle. ( Yes / No )

76 Chapter 5
 Electricity is the flow of electrical energy in a closed circuit. Electrical energy
that flows through a circuit comes from the cell. The stored energy in the cell
changes into electrical energy in the circuit
In a series circuit, the two lamps are placed in one loop. Electrical energy flows

d
through the same path and is shared between the two lamps. Hence, the

Lt
lamps are dimmer.

te
P
Series circuit

In a parallel circuit, the lamps are placed in two separate loops. Electricity flows

on
through two different paths. Each path receives the same amount of electrical
energy from the cell. Hence, both lamps have the same brightness.

ti
The two paths in
this parallel circuit receive
double the amount of
ca
energy compared with the
single path in a series circuit.
This means that the cell in
du

the parallel circuit will

run out faster!
Parallel circuit
E

Since there is only one lamp in each path in the parallel circuit, each lamp in
the parallel circuit receives more electrical energy than each lamp in the series
circuit. So, the lamps in the parallel circuit are brighter.
n
to

Solve this!

The circuit diagrams below show two different circuits.

ls

Circuit A Circuit B
A
)
(c

1 Label the components in Circuit A.

2 What type of circuit does each diagram show? In which circuit will the lamps

be brighter? Worksheet 2 or
kboo
k
W

Heat and Electricity 77

 What substances can conduct electricity?
The ability of a
How do we know substance to conduct
What are some
if a substance can electricity is called
materials that allow
conduct electricity electrical conductivity.

d
electricity to pass
or not?
through?

Lt
te
P
We learnt that
an electrical conductor allows

on
electricity to pass through it while
an electrical insulator does not
allow electricity to pass
through it.

ti
ca
Let’s investigate!
5
cal
experim ent to find out if a material is an electri
Aim: To plan an
du

conductor or insulator.

Materials:
E

 Materials such as paper, rubber band, steel nail, copper nail, brass fastener,
coin, plastic sheet, wood, cotton and pencil lead
n

Wires     Lamp     Cells

What would you
to

observe in the circuit

Instructions: if a material is an
1 Observe each material. Predict which material is
electrical conductor?
ls

an electrical conductor or an electrical insulator.

A

Give reasons.
2 Using the materials given, plan an experiment to test your
)

predictions. Use the following template to help you plan.

(c

Independent variable: ______________________________________

Dependent variable: _______________________________________
Constant variables: ______________________________

78 Chapter 5
 Experimental set-up:

Steps:
___________________________

d
___________________________

Lt
___________________________
___________________________

te
3 Record your observations in a table like this.

P
Is it an electrical Is it an electrical
Material Observation conductor? insulator?
Paper

on
Cotton

Coin

Plastic sheet

ti
ca
4 Then, construct a table with headings to group the materials into electrical
du

conductors and insulators.

Questions:
1 Are your predictions correct?
E

2 How are the electrical conductors similar? ___________________________

3 How are the electrical insulators similar? _____________________________

n

4 Did the result of any of the materials tested surprise you?

to

An exception is
pencil lead that is made
If an electrical conductor is connected to the circuit,
ls

of graphite. Graphite is
the lamp will light up since it allows electricity to pass not a metal but it is an
electrical conductor.
through it. If an electrical insulator is connected, the
A

lamp will not light up since electricity cannot pass

through it.
)

Generally, most metals are electrical conductors and

(c

most non-metals are electrical insulators.

Electrical conductivity of a substance is the ability of
the substance to allow electricity to flow through it. It is
a physical property of a substance.
Heat and Electricity 79
 Science in context

Many objects around us use electricity. Knowledge of electricity and

electrical circuits is important and useful so that we can fix these objects
when they are damaged.

d
Lt
Think-Pair-Share

Use the Internet or books to find out more about jobs that require electrical skills. You can also
interview someone who works with electricity. Create a poster and share with your friend.

te
I am an electrical engineer. I fix
electrical circuits in appliances

P
that are not working. I stay safe by
wearing insulating gloves to protect
myself from getting electrical shocks.

on
ti There is a sensor inside
ca
the dryer that keeps the
Insulating heating system at a certain
gloves temperature. It is called a
du

thermostat. This helps to

We need the electricians to fix the ensure that your clothes in
dryer that is not working. They the dryer are dried properly.
test the heating material with an
E

instrument called a multimeter. The

multimeter measures the amount of
electricity running through the dryer.
n
to
ls

These tools have

different electrical
A

conductivity. Can you

identify parts that are
electrical conductors
)

or insulators?
(c

Solve this!

Which of the following is a good conductor of electricity? Circle.

Aluminium foil   Plastic card   Paper   Silver fork

80 Chapter 5
 Crack the case

Electricity Heat

d
Can pass through Can transfer quickly
electrical through thermal

Lt
Flows in a ___________
___________ ___________
consisting of ___________
such as

te
forming
Can be modelled using Most ___________

P
___________________ with
conventional ___________ Cannot pass Cannot transfer

on
through quickly through
Cell Closed switch electrical thermal
___________ ___________

ti
Battery or cells
Open switch

Wire such as
ca
Most ___________
du

Different types of circuits

Parallel circuit
such as
E

e the
What can Ada do to mak
shine
Series circuit lamps in her doll's house
n

brighter? Tick (🗸).

to

 dd more batteries to the

A
same circuit.
Components are
ls

connected in more  dd more lamps to the

A
than one loop. same circuit.
A

nts
Lamps in a  earrange the compone
R
Components are to form a parallel circuit.
parallel circuit
)

connected in one loop.

will be_________
 se longer wires in the
(c

than those in a U
Electrical energy is shared. series circuit. same circuit.
Lamps will be _________
if we increase the number or
kboo
k
Consolidation worksheet
of lamps.
W

Heat and Electricity 81

 CHAPTER 6 Light

How can the children use mi

rrors to make the corridors
and staircase landings safer
?

d
A

Lt
B

te
P
on
C

E ti
ca
F G
D
du
E
n
to

What Will I Learn

ction when it is reflected from a
Describe how a light ray changes dire
ls

plane mirror.
the appearance of the Moon
Observe and describe the changes in
A

throughout the month.

ction when it travels through
Describe how a light ray changes dire
s as refraction.
different mediums and state this proces
)
(c

Can light tr Where should they

avel
What are the through a w place the mirrors to
all?
properties of Can the dir avoid accidents that
ection
light? How do we of light be could likely happen?
see an object? changed?

82 Chapter 6
 What happens when light is reflected off an object?

Light source

d
Retrace our steps
Light shines

Lt
on an object What do we need to
see things?
How does light travel to
our eyes?
Do you notice Light gets reflected

te
How do we see things
how light travels? It into our eyes that are not sources
travels in a straight line of light?
from a light source!

P
on
ti
Light from the Sun reflects off the surfaces of objects into our eyes.

Light travels in a straight line from a light source like the Sun. When
ca
light from the light source hits the surface of an object, it gets reflected.
When light is reflected, it changes direction and travels into our eyes.
du

How light reflects off a plane mirror

Some objects can reflect light better than others. A plane mirror has
E

a very smooth surface. The smooth surface of a plane mirror is a very

good reflector of light.
n
to

Let’s investigate!
1
observe what happens when light reflects off a plane mirror.
ls

Aim: To
Be careful when
A

Materials: using the ray box. Do

not point the light ray
 Ray box  Blank paper  Protractor at others as this
 Plane mirror  Ruler could hurt their
)

eyes.
(c

Instructions:
1 Using a ray box, shine a ray of light towards the

plane mirror at an angle of 50° between the

mirror and the light ray. Draw your observation
by completing the following diagram.
Light 83
 Plane mirror

What do you
50° notice about the
dotted line in this

d
diagram?

Lt
Light ray

te
Ray box

P
Using a protractor, measure the angles between the light rays and the

on
2

dotted line. Label them in your diagram as Angle a and Angle b.

Angle a = __________°

ti
Angle b = __________°
ca
3 Repeat Step 1 by shining the light ray towards the plane mirror at an angle
of 30° between the mirror and the light ray. Draw your observation by
du

completing the diagram below.

E

Plane mirror What do you notice

about the angle of the
light ray that reflects
n

30° off the mirror? Did the

angle become smaller
to

or bigger now?
Light ray
ls

Ray box
A
)

Using a protractor, measure the angles between the light rays and the
(c

dotted line. Label them in your diagram as Angle c and Angle d.

Angle c = __________°
Angle d = __________°

84 Chapter 6
 Questions:
1 What happens to the direction of the light ray when it hits the plane mirror?

________________________________________________________________

d
2 Compare Angles a and b with Angles c and d. What do you notice?

Lt
________________________________________________________________

Conclusions:
The _______________ of light changes when it hits the plane mirror. The light

te
ray is reflected.
The angle at which the light ray hits the mirror is ( the same as / larger than /

P
smaller than ) the angle of the reflected light ray.

on
Reflected

ti
light ray
ca
Mirror
du

Incoming light ray

E

When light reflects off the surface of an object, the angle formed between the
reflected light ray and the dotted line is always the same as the angle formed
n

between the incoming light ray hitting the object and the dotted line.
to

How light reflects off smooth and rough surfaces

ls
A
)
(c

Smooth plane
mirror A very smooth
surface

When light hits a smooth surface like a mirror, almost all the light is reflected. The reflected rays
bounce off in the same direction. If we stand in front of a smooth surface like a mirror, we see a clear
image of ourselves.

Light 85
 d
Wood

Lt
A rough or uneven surface

When light hits a rough and uneven surface, light is scattered in different directions. If we stand in
front of a rough surface, we do not see a clear image of ourselves.

te
Watch out!

P
When light is reflected off a plane mirror,
there is no change in the colour and shape Image
of the image we see in the mirror. Only

on
the direction of light changes as it bounces
off the surface.
This is why we see a clear reflection of

ti
ourselves in the mirror.
To see a full reflection of ourselves, do we Mirror
ca
need the mirror to be as tall as us? Why or
why not?
du

Solve this!
E

Complete the diagrams to show how light travels when it hits a surface.
n

1 a 1 b

 
to

Two plane
ls

mirrors
Plane mirror
A

2 a
2 b
)

 
(c

Smooth surface Rough surface

kboo
k
or
Worksheet 1
W

86 Chapter 6
 What does the Moon look like on different days of the month?

2 Let’s investigate!

d
Moon appears to change as it orbits Earth.
Aim: To find out how the shape of the

Lt
Instructions: White foam ball
represents the Moon

te
P
Wooden rod
You Light bulb

on
represent represents the Sun
Earth

ti
1 Hold a white foam ball and stand in front 7

of the light bulb so that you, the foam ball 8 6

ca
and the light bulb form a straight line.
2 Then, turn slowly in an anticlockwise
du

direction in a full circle while staying at Sun 5

1
the same spot. Keep the ball directly in (Light bulb)

front of you and slightly above your head.

E

Earth (You)
3 What do you notice about the ball at
2 4
different positions (1 to 8) while you turn?
n

3
Is the ball fully lit, mostly lit, half lit, slightly
to

lit or not lit at all? Draw a diagram to show.

Questions:
ls

1 Did the shape of the ball change as you turn? Circle. ( Yes / No )

2 How much of the ball is lit up at each position? Why does the ball look different
A

at different positions?
________________________________________________________________
)

________________________________________________________________
(c

Conclusion:
The shape of the Moon appears to change because the __________ of the Moon
changes as it orbits the Earth. At different positions, different parts of the Moon
__________ light from the Sun to Earth. Light 87
 The Moon is a natural satellite of Earth. It is made of rocks
Retrace our steps
and does not give off light. We can see the Moon from
Earth because the Moon reflects light from the Sun to the How do we see
the Moon from

d
surface of Earth.
Earth? What is a
At any given time, half the Moon faces the Sun and is lit up satellite?

Lt
by the Sun. The other half of the Moon that does not face
the Sun remains dark.

te
This is the shape
of Moon seen

P
from Earth!
Waning crescent

on
ti
ca
At this position, the
Moon is in between the New Moon
Earth and the Sun.
The side of the Moon that
du

is dark faces the Earth,

while the side of the Moon
that is lit up faces away
from the Earth. We call Half the Moon
E

this a new Moon. During is always

this phase, the Moon is facing the Sun.
not visible from the Earth.
n
to
ls
A

Waxing
crescent
)
(c

On Earth, we can only see a small

part of the brightly-lit side of the Moon.
This is called a crescent Moon.

88 Chapter 6
 The Moon takes about one month to orbit the Earth. As the Moon orbits
Earth, it changes position. As it orbits, we see different amounts of the
brightly-lit side of the Moon from Earth. Hence, the Moon appears to change

d
its shape every day throughout the month. This apparent change in the

Lt
shape of the Moon is also called the different phases of the Moon.  

At this position, the Earth is in

te
Third quarter between the Sun and the Moon.
The side of the Moon that is lit
Waning gibbous up faces the Earth, while the

P
side of the Moon that is dark
faces away from the Earth.
We call this a full Moon. During
this phase, we see the Moon

on
appearing like a complete circle.

ti Full
Moon
ca
du

Earth
E
n

Orbit of Moon
to

Waxing
ls

gibbous
A

On Earth, we can see more than half

First quarter
of the brightly-lit side of the Moon.
This is called a gibbous Moon.
)
(c

On Earth, we can see half of

the brightly-lit side of the Moon.
This is called a half Moon.

Light 89
 Solve this!

1 Draw in the boxes to show the Moon phases we would see on Earth when
the Moon is in the different positions.

d
Lt
Light rays from
Moon the Sun

Earth

te
P
on
ti
ca
2 Name the different phases of the Moon.
du
E
n
to
ls
A
)
(c

kboo
k
or
Worksheet 2
W

90 Chapter 6
 What happens when light travels through transparent and
translucent objects?
Think-Pair-Share

d
Look around you. What types of materials do you think light can pass through?

Lt
The space or material where light travels through is referred to as the medium.
When light hits transparent and translucent objects, light can travel through
these objects. Transparent mediums allow most of the light to pass through

te
while translucent mediums allow some light to pass through.
I can see the

P
The lenses on my glasses picture of the rabbit at the I can see the trees outside
are made of a transparent bottom of the cup because the house through the
plastic. So is the front part of water is transparent. glass windows. I wonder

on
the picture frame! I can see Light can travel what happens when light
through both of them. through it! rays travel through the
glass panels?

ti
ca
du

Air, water, clear plastic and glass are examples of mediums where light can
E

travel through.
n
to

Let’s investigate!
3
hen it travels from one medium to another.
ppens to light w
Aim: To find out what ha
ls

Materials:
A

We need to make this a

Ray box fair test! What should we take note
of about the size of the glass block,
Transparent rectangular container plastic block and transparent
)

container?
Oil
(c

Water
Glass block
Clear plastic block
White paper
Light 91
 Instructions:
1 Place a glass block on a piece of white paper. Shine a ray of light through

the glass block. What did you observe? Draw your observation in the
diagram below.

d
Ray box

Lt
Glass block

te
2 Replace the glass block with a plastic block. Repeat Step 1.

P
Ray box

on
Plastic block

ti
ca
3 Replace the glass block with a transparent container filled with oil or water.
Repeat Step 1. Label in the diagram which medium you used.
du

Ray box
E

Container filled with

___________
n
to

Questions:
1 What are the mediums that light can travel through? Tick (🗸).
ls

Air   Water   Oil   Plastic   Glass

A

2 Did the light ray continue to travel in the same direction when it entered
another medium from the air? ______________________________________
)

________________________________________________________________
(c

3 Did the light ray continue to travel in the same direction when it exited the
medium into the air? ______________________________________________
________________________________________________________________
92 Chapter 6
 This bending of light when light travels from one medium to another is called
refraction.
When light travels from one medium to another, it moves faster or slower,
causing it to change direction and bend.

d
Lt
Light bends this way as it travels Light bends differently as it travels
from air to glass. from glass to air.

te
More
than

P
Air 180°
Glass block
Less

on
Refracted
light than
180°
Glass block
Air

ti
Refracted
light
ca
Here, light entering glass travels Here, light entering air travels
slower and bends. faster and bends.
du

Refraction can cause objects to appear bent

Can we observe refraction in real life? What happens when we put a pencil into
a transparent beaker filled with water?
E

When we look at a pencil in water, the pencil appears to be bent. The pencil
appears bent because of refraction.
n
to

2 As light travels in a straight line, when the

refracted light enters our eyes, our brain
No, it is not thinks that the tip of the pencil is here.
ls

broken.
A

Is the pencil
broken?
1 Light ray travels
from the pencil tip,
)

through the water

(c

and into the air.

Light bends when it
travels from water
to air.

Light 93
 Refraction can cause objects to appear reversed

Think-Pair-Share

Fill a transparent glass with water. Draw an arrow pointing to

d
the right on a piece of paper. Place the arrow behind the glass
of water.

Lt
Observe what happens to the direction of the arrow.
What is happening to the light as it travels through the water?

te
Standing in front
of the glass If the container is
looking at the

P
Glass of water not curved, but a
from above arrow rectangular box,
will the arrow still

on
be reversed?

Arrow

ti
ca
Light is refracted twice when travelling through the cylindrical glass of water.
Due to the shape of the glass, the light rays bend so much that they cross
du

paths when they exit the glass of water. The image of the arrow that we see
becomes reversed.
E

Solve this!
n

Cyrus dropped a coin into an opaque cup. He could not see the coin from
where he stood. Next, Vera pours some water into the cup. Now, Cyrus can see
to

the coin! Complete the diagram below to show how the light ray travels such
that Cyrus could see the coin after water is poured.
ls
A

Cyrus could not Cyrus can see the

see the coin. coin now.
)
(c

kboo
k
or
Worksheet 3
W

94 Chapter 6
 Crack the case

Light

d
 Travels in a
_________ line _________ when it

Lt
hits an object
 Changes direction _________ or bends
when it meets when it travels from
a surface or

te
a b one _________ to
another medium another

P
Angle __ = Angle __
causing
The Moon
such as

on
Rough objects
Smooth objects
Different amounts of

ti
light from the Sun are
reflected from the Moon such
as Light rays Light rays are
ca
into our eyes. This allows are reflected reflected in
us to see the different in _________ _________
_________ of the Moon. direction. We directions. We
du

_________ a _________ a
Plane mirrors clear image. clear image.
E

Objects in water
to appear
n

_________
What can the children do to make the corridors
to

and staircase landings safer? Objects

They can place mirrors at locations ___________. to appear
ls

Why? Tick (🗸). _________

 ight can reflect off the children and into the
A

L
mirrors.
Light can reflect off the mirrors and allow the
)

children to see their own images.

(c

Light can reflect off the mirrors and allow the

children to see the images of others.
Light can refract through the mirrors and kboo
k

allow the children to see the images of others.

or
Consolidation worksheet
W

Light 95
 CHAPTER 7 Chemical Changes
Tim's parents have been aw
ay on a holiday for two week
fruits left on the kitchen coun s. Tim notices some

d
ter and calls his mother to as
k if he can eat them.

Lt
I can see some

te
changes on some
of these fruits! How
do I tell the ones

P
that are still good?
You can eat the fruits
but if some of the fruits

on
are not good, please
throw them away!

ti
ca
du
E
n
to
ls

Is the rotting of
A

fruits a chemical
What Will I Learn change or a physical
Describe what chemical reactions are change? Can it be
)

and write them as word equations. reversed?

(c

t
Observe and describe the evidence tha What are some
a chemical reaction has occurred. indicators that a
chemical reaction
has taken place?

96 Chapter 7
 What is a chemical reaction?
Think-Pair-Share

Crumple a piece of paper into a ball. What has happened to the paper? Your teacher

d
will burn another piece of paper. Observe what happens to this piece of paper. Which
is a physical change and a chemical change?

Lt
Retrace our steps

te
What are physical
and chemical
changes?

P
on
When a piece of paper is crumpled, a force is applied to change its

ti
shape. However, we can easily return this paper to its original form by
ca
unfolding it. This change is reversible. Since no new substances are
formed, it is called a physical change.
du

When a piece of paper is burnt,

black ashes are formed and we
can see smoke. The ashes formed
E

are different from the paper in their

colour and texture. Ash is the new
substance formed. The change
n

cannot be reversed, so it is not

to

possible to change the ashes back When papers are burnt, the ashes
produced are black and brittle.
to paper again.
ls

During burning, new substances are formed. We say that burning is a

chemical change. In this process, the paper reacts with oxygen in the
A

air. The chemical reaction between paper and oxygen is also known as
combustion.
)

Think-Pair-Share
(c

You will be given a candle. What do you think will happen when the candle is lit?
Discuss with your friends and write down a list of questions that you have about the
burning candle. Light up the candle. Do you observe any changes as the candle burns?
Are these changes physical or chemical?

Chemical Changes 97
 When a candle is lit, the heat causes the wax to melt. There is a change in state
of the wax from a solid to a liquid. We have learnt that a change of state is a
physical change.

d
However, the burning of a candle is more than just the melting of the wax. It is also

Lt
a combustion reaction. During combustion, wax reacts with oxygen in the air to
produce new substances like carbon dioxide and water vapour. As new substances
are formed, combustion is a type of chemical change.

te
We can represent a chemical reaction using a word equation. A word equation can
tell us the reactants before the chemical reaction occurs and the products formed

P
after the reaction has occurred.

on
Wax + Oxygen ➔ Carbon dioxide + Water vapour

ti
Reactants Products
ca
Since wax changes its
du

state and new substances

are formed when we burn
The flame causes candles, the burning of a
the wax to melt. The candle is both a physical
Wick
E

melted wax flows up and chemical change!

the wick and burns
through combustion. Liquid
wax
n

Solid
wax
to
ls
A

Oh no, my paper
lantern!
)
(c

98 Chapter 7
 Solve this!

Charcoal is burnt in a barbecue pit to cook food. Charcoal is first broken into

d
smaller pieces, then it is placed inside the pit to burn. When charcoal is burnt, it

Lt
reacts with oxygen in the air to produce carbon dioxide gas and water vapour.
1 Identify the physical change and chemical change in this scenario.
Physical change: _________________________________________________

te
Chemical change: ________________________________________________

P
2 Write down the word equation for the chemical reaction. Label the
reactants and products in your word equation.

on
ti or
kboo
k
Worksheet 1
ca

W
du
E
n
to
ls
A
)
(c

Chemical Changes 99
 What evidence can tell us that a chemical reaction has taken place?

We can look out for

We have learnt that new evidence that can

d
substances are formed tell us that a new
during a chemical reaction. substance is formed!

Lt
How can we tell when this
happens?

te
P
During a chemical reaction, there can be evidence or indicators that tell

on
us that new products are formed. These indicators help us to infer that a
chemical reaction has occurred.

ti
Colour change and odour change
Sometimes, a chemical reaction can cause a colour change or an odour
ca
change. The change in colour or odour can be an indicator that new products
are formed, signalling that a chemical reaction has occurred. We can use our
du

sense of sight and smell to observe these changes during the reaction.
E

Let’s investigate!
1
n

at.
the odour and colour of sugar change with he
Aim: To find out how
to

We should not smell

Materials:
ls

a chemical reaction
Half a cup of sugar up close. Instead, we
should gently wave
A

Cooking pot What steps should the smell towards

we take to carry out our nose.
Stove a chemical reaction
safely?
Spoon or stirrer
)
(c

100 Chapter 7
 Instructions:
1 Pour some sugar into the cooking pot. Observe

the colour and smell of the sugar.

Put the pot on a stove and heat it at low heat.

d
2

Stir the sugar while heating. Continue stirring

Lt
3

until you observe some changes. Record your

observations in the table below.

te
Before heating After heating
Colour of sugar Smell of sugar Colour of sugar Smell of sugar

P
on
Questions:
1 Did the colour of the sugar change after heating? __________

ti
2 Did the smell of the sugar change after heating? __________
Is a new substance formed after the sugar is heated to a very high
ca
3

temperature? How can you tell? ____________________________________

du

Sugar usually has a faint

After we heat melting sugar to a high enough sweet smell. After the
temperature, we observe that the colour of the chemical reaction has
E

sugar has changed from white to brown. The smell occurred, the smell becomes
buttery and nutty!
of the sugar also changes. These
observations let us know that a
n

new substance is formed. So, we

to

say that the change of colour and

odour are indicators that a chemical
ls

reaction has occurred when we heat

melting sugar.
A

During a chemical reaction, a

Sugar undergoing a chemical
substance changes and becomes reaction after being heated
)

a new substance with different

(c

properties.

For example, after an apple is exposed to

oxygen in the air, it undergoes a chemical
reaction and changes colour. We can
observe that a new substance is formed.

Chemical Changes 101

 Science in context

Sometimes, fuels in cars do not have enough oxygen to burn properly or

completely. The chemical reaction will then produce soot and harmful gases like

d
carbon monoxide.

Lt
Catalytic converters are fitted in cars to help change the harmful substances
into something less harmful. These catalytic converters do so by carrying out
chemical reactions as well! The products released from the catalytic converters

te
are less harmful to us and our environment.
I see black smoke
coming out of these cars!

P
The colour change is an
indicator that tells us that a
new substance, soot,

on
is formed.

ti
ca
du

Watch out! Does a colour change

or an odour change
Sometimes, colour change may be seen even when there is no always mean that a
chemical reaction occurring.
E

chemical reaction has

For example, when we mix different coloured inks together, the happened?
mixture we get has a different colour. This does not mean that
a chemical reaction has happened because we can reverse
n

this process. We can separate the ink into the

different colours that make up the mixture. Since
to

we can reverse the process, this means that no

new substances are formed. This tells us that the
mixing of paints is a physical change.
ls

Watch this video to see how this process can be

reversed!
A

Temperature change and formation of gas

)
(c

We have learnt that mixing

vinegar and bicarbonate of soda
will result in a chemical reaction.
What are some indicators that tell
us that a chemical reaction has
occurred?

102 Chapter 7
 Let’s investigate!
2
egar is added to bicarbonate of soda.
ppens when vin
Aim: To observe what ha

d
Materials:

Lt
Tray Measuring cylinder
Bicarbonate of soda Thermometer
Empty plastic bottle Balloon

te
Vinegar

P
Instructions:

on
1 Place the empty plastic bottle on the tray.

2 Using the measuring cylinder, measure 10 cm3 of vinegar and pour it into
the plastic bottle. Use a thermometer to measure the temperature of the
vinegar.
ti
ca
Temperature = _____ºC
3 Scoop 1 teaspoon of bicarbonate of soda into the plastic bottle. Observe
du

any changes. Place a balloon quickly over the mouth of the bottle.
4 Draw and describe what you observed in the set-up. Label the reactants
E

and products.
n
to
ls
A
)
(c

5 After adding bicarbonate of soda to the vinegar, measure the temperature

of the substances.

Temperature = _______ºC

Chemical Changes 103

 6 Carefully remove the balloon by pinching the ends of the balloon and tying
a knot. Look for an appropriate instrument to find out the mass of what is
stored inside the balloon at the end of the experiment.
Describe your steps below.

d
Lt
te
P
on
ti
How can you tell that this reaction has formed a new substance? Discuss
with your classmates.
ca
Questions:
1 A gas is formed from this reaction. Name the gas.
du

________________________________________________________________

2 How do you tell that this gas is formed?

E

________________________________________________________________
n
to

Not all chemical reactions show colour change or You can also gently
odour change in the substances. Some chemical touch the sides of
reactions show other indicators such as a change the container to
ls

feel the change in

in temperature or the formation of bubbles. temperature.
A

When we add bicarbonate of soda to vinegar,

they react to produce carbon dioxide and sodium
)

acetate, which are new substances.

(c

During this reaction, the temperature of the

surroundings decreases.

104 Chapter 7
 Another name for
vinegar is acetic
acid. Another name
for bicarbonate of
soda is sodium
We observe bicarbonate.

d
bubbles due to
the formation of

Lt
carbon dioxide
gas during the
chemical reaction.

This reaction can be represented using a word equation.

te
Sodium bicarbonate + Acetic acid ➔ Carbon dioxide + Sodium acetate
Watch out!

P
Sometimes, we can see
I see bubbles in this bubbles appearing even though a

on
fizzy drink! Is this a chemical reaction did not occur. These
chemical reaction? gas bubbles are not produced from a
chemical change. The gas is carbon
dioxide dissolved in the fizzy drink! When

ti
we open the can, the dissolved carbon
dioxide escapes from the
drink as bubbles!
ca
du

Solve this!
E

The iron bars are exposed to air and moisture for two weeks and have
undergone a chemical change.
n
to
ls
A

How the iron bars looked like at first How the iron bars look like now

Which indicator tells you that a chemical reaction has occurred?

)

________________________________________________________________
(c

2 Write a word equation for this chemical reaction.

________________________________________________________________
kboo
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or
Worksheet 2
105
W

Chemical Changes
 Crack the case

Chemical Reactions

d
involve can be

Lt
The interaction of substances called
_______________ to form new substances Represented using
word equations

te
called _______________

P
on
A  +  B  ➔  C  +  D

______________ ______________

ti
ca
for example
du

_________ + Sodium bicarbonate ➔

Iron + Oxygen + Water ➔ _________
_________ + Sodium acetate
E
n
to
ls
A

Wood + Oxygen ➔ _____________ + Water vapour

)
(c

106 Chapter 7
 can be
Observed with some indicators

d
Lt
_______________ produced _______________ change

te
P
on
___________ change and ___________ change

ti
ca
du
E
n

).
does Tim know wh ich fru its to throw away? Tick (🗸
How
to

tions
ed to throw th e fruits aw ay because chemical reac
No ne
can be reversed.
ls

has gone bad.

Smell each fruit to see if it
A

d.
k at the colour of ea ch fruit to see if it has gone ba
Loo
if it has gone bad.
Squeeze each fruit to see
)

see if it has gone bad.

(c

peratu re of ea ch fruit to
Feel the tem

kboo
k
or
Consolidation worksheet
W

Chemical Changes 107

 CHAPTER 8 Dissolving
Vera is having some friends
over for a party. Her friends
minutes. Vera is preparing so are arriving in a few
me iced drinks and trying to

d
sweeten the drinks. She decid find something to
es to make a brown sugar so
sugar to cold water. lution by adding brown

Lt
te
My friends are
arriving soon! This

P
does not look right...
What should I do?

on
ti
ca
du
E
n
to
ls
A

What Will I Learn

s dissolving in liquids and use
Describe how temperature affects solid
)

s.
particle model to describe the proces
What can Vera do
(c

What is the solute to make the brown

What is the sugar solution
and solvent here?
problem that as quickly as
What affects how fast
Vera is facing? possible?
a solute dissolves in a
solvent?
108 Chapter 8
 Is dissolving a physical change or a chemical change?

Retrace our steps

d
How do we tell if a physical or a chemical
change has occurred? Do chemical changes

Lt
always occur when we add substances
together? My sugar is no longer
My sugar seems to white! Look at this
have disappeared. brown sticky substance!

te
Is this a chemical It smells nice! Is a new
change or a substance formed?
physical change?

P
on
1 Let ’s investigate!
ti
ca
Aim: To find out if dissolving is a physical or a chemical change.
du

Materials:
Salt Stirrer Metal plate Tripod stand
E

Water Two beakers Bunsen burner Retort stand

n

Instructions:
1 Observe the salt and water given to you. Describe and draw what
to

they look like.

ls
A
)
(c

2 Add some salt to the beaker of water. Stir the mixture until all the salt
has dissolved.
Dissolving 109
 3 Heat the beaker of salt water using a Bunsen burner. Place a cool metal
plate at an angle above Beaker 1, with Beaker 2 on the side. Your set-up
should look like this:
Retort stand

d
Be careful when
Cool metal plate
using the Bunsen

Lt
burner or during
heating.
Beaker 1

Salt water

te
Beaker 2

Tripod stand

P
Bunsen burner

on
4 Heat until no more water is left in Beaker 1. Observe what is left in
Beaker 1 and what is collected in Beaker 2. Draw and describe your
observations below.
ti
ca
du
E
n

Questions:
to

1 Compare your observations in Step 1 and Step 4. Are the substances

the same? __________

ls

2 What are the substances collected in the beakers in Step 4 likely to be?

Beaker 1: __________
A

Beaker 2: __________

Conclusion:
)

The solute and solvent collected at the end are the __________ as the
(c

substances used at the start. When salt dissolves in water, ( no new substances
/ new substances ) are formed. As such, dissolving is a ( physical / chemical )
change. Substances ( can / cannot ) return to their original forms, hence
dissolving a substance is a ( reversible / irreversible ) process.
110 Chapter 8
 Adding a substance to another substance does not
always result in a chemical reaction. For example, when Retrace our steps

we dissolve a solute in a solvent, particles of the solute

What happens
are mixed with the solvent. When the particles are evenly
to the particles

d
mixed, a solution is formed. The solute and solvent in the of a solid when
solution have not changed. Since no new substances it dissolves in a

Lt
liquid?
are formed in this process, no chemical reaction has
occurred. Dissolving is a physical change.

te
Salt solute

P
on
Water
solvent 1. Arrangement 2. As water 3. After a while, 4. After we heat the salt
of salt and water particles move the salt particles solution, we obtain salt
particles at the around one are evenly mixed and water again. No new

ti
start another, they with the water substances are formed.
pull the salt particles. We say
Water particle particles apart. that the salt has
ca
Salt particle fully dissolved in
water.
du

Solve this!

Jimmy has some salt and baking powder. He wants to find out what happens
when they are added to water. Jimmy stirs salt into the first beaker of water
E

while he stirs baking powder into the second beaker of water. Both solids seem
to disappear in the water. Jimmy observes bubbles forming in the beaker
n

containing the baking powder. When Jimmy heats the beaker containing the
baking powder, more bubbles appear. When he heats the salt solution, he
to

obtains a white and dry solid that looks and tastes like salt.
ls

1 Which pair of substances underwent a physical change?

________________________________________________________________
A

2 Give reasons for your answer.

)

________________________________________________________________
(c

________________________________________________________________

kboo
k
or
Worksheet 1
W

Dissolving 111
 How does temperature affect how solids dissolve in liquids?

My hot tea tastes

How did your sugar
sweet after dissolving the
cube dissolve so

d
sugar cube! The property
quickly? I can still
of sugar is still present
see the sugar cube

Lt
after mixing.
at the bottom of my
cold tea!

te
What effect does
temperature have
My hot tea has
on dissolving?
already dissolved

P
two sugar cubes!

on
ti
ca
Can temperature
affect how much
and how fast sugar
du

dissolves?

Temperature affects the amount of solid that can fully dissolve in a liquid
E
n

Let’s investigate!
2
nt of
water affects the amou
to

w the tem pe rature of

Aim: To find out ho
olve in water.
sugar that can fully diss How do you tell that
ls

the beaker of water has

Materials: fully dissolved the sugar?
A

What will you observe

if an additional amount
of sugar is added to this
beaker of water?
)

Beakers of water at three Sugar Thermometer Stirrer

(c

different temperatures

Instructions:
1 Plan an experiment to find out how the temperature of

water can affect the amount of sugar it can fully dissolve.

112 Chapter 8
 2 Use the following questions to guide you in your plan.
a What is the independent variable?

______________________________________________________________
What is the dependent variable?

d
b

______________________________________________________________

Lt
c What variables are you going to keep constant?
______________________________________________________________

te
d How are you going to measure the temperature of water?
______________________________________________________________

P
e How are you going to measure the amount of sugar?
______________________________________________________________

on
3 Predict how the temperature of water will affect the amount of sugar it can
fully dissolve.

ti
______________________________________________________________
ca
4 Carry out your plan. Record your results in the table below.
We can put
du

our dependent
We can put our variable here.
independent
variable here.
E
n
to

5 Plot a line graph to show the amount of sugar that can be fully dissolved at
different temperatures.
ls
A
)
(c

Dissolving 113
 The temperature of the
Question: water can change very
quickly. What can you
Did your results match your prediction? ( Yes / No ) do to ensure that your
results are as accurate
as possible?
Conclusion:

d
As the temperature of the water ____________,

Lt
the amount of sugar that can be fully dissolved
in the water ____________.

te
As temperature increases, the solid particles in the solute and the liquid
particles in the solvent gain more energy. With more energy, the solid particles

P
vibrate faster and are less held together. With more energy, the liquid particles
move faster and collide with more solid particles. This allows the liquid solvent

on
particles to pull more solid solute particles apart, causing a greater amount of
solute to be dissolved.

ti
Therefore, at higher temperatures, a greater amount of solute can dissolve in
ca
the solvent.
20 ºC 80 ºC
du

Sugar
E
n
to

Water Both water at 20 ºC and 80 ºC can fully dissolve 200 g of sugar.

ls

20 ºC 80 ºC
A
)
(c

Water at 80 ºC can fully dissolve 400 g of sugar but water at 20 ºC cannot.

114 Chapter 8
 Temperature affects how fast solids dissolve in a liquid

Let’s investigate!
3

d
r
m : To find out how the temperature of wate
Ai
can dissolve in water.

Lt
affects how fast sugar

Materials:

te
 Beakers of water at three Stopwatch
different temperatures Thermometer

P
Sugar cubes Stirrer Cold Room Hot
temperature
Instructions:

on
1 Predict how the temperature of water will affect how fast a sugar cube can

dissolve. ________________________________________________________

ti
2 Measure and record the temperature of water in each beaker in the table.
3 Add one sugar cube to the beaker of cold water Take note of the
ca
number of times you
and start the stopwatch. Stir.
stirred to fully dissolve the
4 Once the sugar cube has fully dissolved, stop the sugar cube.
du

stopwatch and record the time taken in the table below.

5 Repeat Steps 3 and 4 for the other beakers. Stir the same number
E

of times as Step 3.
Temperature of water (ºC) Time taken for sugar cube to dissolve (___)
n
to

Plot a line graph below to present your results.

ls

6
A
)
(c

Dissolving 115
 Questions:
1 How do you tell how fast or slow the sugar cube dissolves?

For the same amount of sugar, the longer the time taken for it to dissolve
means the ( faster / slower ) the sugar cube dissolves.

d
2 Did your results match your prediction? ( Yes / No )

Lt
Conclusion:
When the temperature of the water ______________, the sugar cube dissolves

te
______________ in water.

P
As temperature increases, the solid particles in the solute and liquid particles
in the solvent gain more energy. With more energy, the liquid particles move

on
faster and collide with the solid particles more frequently. This allows more
chances for the liquid particles to pull the solid particles apart. So, the solute
can be broken apart in a shorter time, causing it to dissolve faster.

ti
ca
Therefore, in solvents of higher temperatures, solutes dissolve more quickly.
du

20 ºC 80 ºC
Sugar
E
n

Water
to
ls
A
)
(c

Within a given length of time, the water particles at a higher temperature collide with
the sugar particles more frequently than the water particles at a lower temperature.

116 Chapter 8
 Let us role-play to I represent a particle in a
understand how solute! The rest represent
temperature affects the particles in a solvent! How

d
dissolving of a solute in should we move if the
a solvent! temperature increases?

Lt
te
P
on
Will we bump
Will we bump into
into more friends,
Tim more frequently

ti
including Tim, if
if the temperature
the temperature
increases?
increases?
ca
Watch out!
du

Cold drinks can still

dissolve sugar. It just
Since my tea is takes a longer time to
hot, can I dissolve dissolve. To make the
E

any amount of sugar dissolve faster,

sugar in it? you can stir the
mixture!
n
to

My cold tea tastes

ls

bland. Do I need to heat

A solvent at a higher the tea first before I can
temperature may allow more solute
A

dissolve sugar in it to
to dissolve but this does not mean that make it sweet?
the solvent can dissolve any amount of
solute. There is a limit to the amount
)

of solute the solvent

(c

can dissolve!

Think-Pair-Share

We have learnt that stirring helps to dissolve a solid faster in a solvent. Using your
knowledge of particle model, explain how stirring affects how fast solids dissolve in liquids.

Dissolving 117
 Solve this!

Chan conducts an experiment to find out how the temperature of water

affects the time taken for 20 g of salt to dissolve in water at different
temperatures. He stirs each beaker of solution the same number of times.

d
Lt
te
20 °C 40 °C 60 °C 80 °C

P
He plots his results in a graph shown below.

on
Time 50
(s) 45 In a line of best fit,
40 we try to balance
the points on

ti
35 both sides of the
30 straight line in
ca
25 the graph.
20
15
du

10
5
0
E

20 40 60 80
Temperature
(°C)
n

1 Help Chan draw a line of best fit in the graph above.

to

2 Describe the pattern shown by his results.

ls

________________________________________________________________
________________________________________________________________
A

3 Using the particle model, explain the pattern stated in 2 .

)

________________________________________________________________
(c

________________________________________________________________

________________________________________________________________
kboo
k
or
Worksheet 2
W

118 Chapter 8
 Crack the case

Dissolving
is a is affected by

d
Lt
Physical change Temperature

affects

te
P
No new substances The amount of solute How fast a solute
are formed that can dissolve fully can dissolve in
a solvent

on
in a solvent
for example

When a solid is dissolved ti

ca
in a liquid, the solid and
liquid in the solution do At higher temperatures, At higher temperatures,
________ solids can be
du

solids can dissolve

not change.
dissolved in a liquid. ________ in a liquid.
E
n
to

in
sh ould Vera do to m ak e her brown sugar solution
What
).
time for the party? Tick (🗸
ls

n sugar to the water.

 he should add more brow
S
A

own sugar in water.

 he should not stir the br
S
should stir the brown sugar in colder water.
 he
S
)

sugar in hot water.

 he should stir the brown
(c

kboo
k
or
Consolidation worksheet
W

Dissolving 119
 CHAPTER 9 Rocks and Soil

Why is this pot leaking

water? Why are my plants

d
not growing well? Did you use only the
material from this bag for

Lt
your potted plants?

I thought

te
all rocks were hard!
Why does my rock keep
y
CIa breaking? What should

P
I use to loosen
SiIt the soil?

on
Sand
ti
ca
du

What can Tim do to help his

tomato plants grow
well? What rock can Vera us
e to loosen the soil?
E
n

What Will I Learn

to

Classify rocks as metamorphic, igneous and sedimentary, and descri

be the features of each
type of rock.
Describe the rock cycle and the formation of metamorphic, igneou
ls

s and sedimentary rocks.

Describe how fossils can form in sedimentary rocks.
A

Classify soils based on their clay, sand and organic content.

Describe how the change in soil composition can affect plant growt
h.
)

Why are Tim’s What is soil made What

(c

g
plants not growin of ? What mixture properties of
of can help Tim rocks can help
well? What type
material did Tim grow his tomato Vera to loosen
use? plants well? the soil?

120 Chapter 9
 Retrace our steps
How can we describe rocks?
Name some rocks
Rocks are made up of grains of minerals. The you have learnt
grains in a rock can have different colours, shapes about. What are

d
and sizes, giving each rock its unique properties. some properties
they have?

Lt
Think-Pair-Share

Walk around the neighbourhood. Touch and look at some rocks.

Observe and describe the texture, size and colour of the rock. Do they feel and look

te
the same? Do you think they are made up of the same materials?

P
Rocks have different types and arrangements of grains
We can describe rocks by looking at their grains. Some grains

on
are visible to our eyes. Some grains are too small and we need a
magnifying glass or microscope to see them. We can also look at the
arrangement of grains in the rock.

ti
There are
some gaps between
the rounded grains
ca
in sandstone.
du

Granite has large mineral Sandstone has large but

E

grains tightly fitted together. rounded mineral grains.

n
to

I cannot see the grains in

my limestone! They are so This structure is
small and fine! made of limestone!
ls

Can you guess how this

arch collapsed?
We are in Malta! The
A

Azure Window looks

magnificent! But, part of it
collapsed in 2017!
)
(c

Limestone also has

rounded grains with gaps
between them. Water can
run through it easily.

Rocks and Soil 121

 How the grains are arranged in a rock can affect the amount of gaps and
spaces between the grains in the rock. This can determine if the rock can hold
water or allow water to pass through it.

d
Having no gaps between These gaps can hold or
the grains makes the store water. Rocks with gaps

Lt
rock non-porous. between the grains are porous.

te
P
on
ti
ca
du

If the grains are packed If the grains are loosely packed,

tightly, water cannot water can flow through easily.
pass through easily. We say the rock is permeable.
E

Think-Pair-Share

Watch the video to see how we can test rocks to find out if they are
n

porous or permeable. You can carry out your own tests on rocks you
find too!
to
ls

What are the types of rocks?

A

There are three different types of rocks — igneous, sedimentary and

metamorphic rocks. These rocks can be formed due to physical changes and,
)

sometimes, chemical changes. As there is a large variety of rocks with different

(c

properties, we can classify rocks according to how they are formed.

Porous – Having spaces within to hold fluids like water

Clues Permeable – Having spaces within that allow gases or fluids like water to pass through

122 Chapter 9
 Think-Pair-Share

Using the Internet or books, research to find out about igneous, sedimentary and metamorphic
rocks. Use the guiding questions below:

d
What type of grains do they have?
What conditions and processes are involved in the formation of each type of rock?

Lt
Choose one rock for each type. Draw and label the features of each rock you chose.

Igneous rocks

te
Igneous rocks are formed from molten rock or magma that has cooled and
solidified to become a solid.

P
The ways magma cools underground and on the surface are different.
Magma underground usually cools slowly to form rocks. These igneous rocks

on
often have large or coarse mineral grains. As the magma cools slowly, the
minerals in the rock have time to grow into crystals.

ti
Magma that flows out of the volcano is called lava. Lava usually cools quickly
and solidifies into fine-grained rocks or rocks with air bubbles. Sometimes,
ca
lava cools so quickly that little or no crystals can be formed. This is because
crystals do not have time to form in these igneous rocks.
du

Rock formed when magma cools Rocks formed when lava cools quickly
slowly
Smooth and Air bubbles due
Fine grains
glassy to gases in lava
E

Crystal

Coarse grains
n

Granite Basalt Obsidian Pumice

to

Examples of igneous rocks

Obsidian has been used

since ancient times to
ls

make weapons because

it has sharp edges!
A
)
(c

Clues Coarse – Rough in texture

Rocks and Soil 123

 Sedimentary rocks
Rocks break down into smaller pieces called sediments. The process of
breaking down is called weathering.

d
Wind and rain help to carry sediments to be deposited over land and in

Lt
water. When sediments are carried away by wind and water and deposited
elsewhere, this process is known as erosion.

te
Sedimentary rocks are formed by
layers of sediments. These layers

P
are piled on top of one another.

on
This is the Rainbow

ti
Wow! The sediments have
Mountain in Peru.
been deposited in layers
Look at the layers of
over the years.
ca
sediments!

3 As the sediment layers

du

stack on top of each other,

their weight squeezes the
layers together. After a
E

long time, sedimentary

Retrace our steps rocks are formed.
n

What are the

different types
to

of fossils we After a living thing like a shark Most of its body parts and
have learnt dies, it is buried by sediments. remains are broken down,
about? leaving the hard parts, like
ls

its skeleton, behind.

A

It is very rare for

living things to become
fossils. After living things
)

die, their bodies are usually

broken down over time by
(c

other living things such as

bacteria and fungi. We call
this process decaying.
Example of how a fossil is formed over time

124 Chapter 9
 Retrace our steps

Sedimentary rocks are often found to contain fossils. Is squeezing or

How are fossils formed in sedimentary rocks? breaking down rocks
into smaller pieces a
physical or chemical

d
change?
After sediments are deposited in water, they

Lt
1

settle to the bottom in layers and are buried.

This process is known as sedimentation.

te
2 Dead plants and animals trapped between

P
the layers of sediments become fossils.

on
ti
ca
Fossils are the preserved remains,
traces or impressions of living
du

things that were once alive. This

includes bones, skins, shells, hair
and even footprints.
E

To form fossils, the body of the

n

living thing must stay away from

heat, water and air. Hence, fossils
to

As more layers of sediments After a long time, due to

are piled on top of one Earth’s movement, this are usually found in sedimentary
another, the sediments sedimentary rock with the rocks because they are pressed
ls

around the skeleton are fossilised shark may appear

squeezed, turning it into on Earth’s surface. tightly in between the layers.
a sedimentary rock.
A

Fossils can even include remains

of animals and plants from a few
millions years ago during the
)

Ice Age!
(c

Sediments – Solid materials that are carried away and placed in a new location
Clues Deposit – To leave and place something at a location
Decay – To break down due to the action of bacteria, fungi or other living things

Rocks and Soil 125

 We can see layers in a sedimentary rock.

Splits easily Layers

d
into layers

Lt
Shale Sandstone

Examples of sedimentary rocks with a layered pattern

te
If a sedimentary rock is mostly made up of one type of mineral

P
or has very fine grains, it may not have visible layers.

on
Siltstone is made up of very fine grains.

Siltstone

Sedimentary rocks are also the only type of rock that may contain fossils of
animals or plants.
ti
ca
Limestone feels I can see the
powdery because it Can you find the coarse grains on
du

has fine grains. fossils in these this sandstone!

rocks?
E
n
to

Limestone Sandstone

Examples of sedimentary rocks with fossils trapped inside

ls

Fossils are useful as they give scientists some ideas on how living things and
A

the environment have changed over time.

Think-Pair-Share
)

Using the Internet or books, research to find out how fossils can inform us about the changing
(c

Earth. Use the guiding questions below:

How long ago was the first fossil found?
What does the place where the fossil was found tell us about how it was formed?
What does the formation of fossils tell us about changes to the climate at that particular place?

126 Chapter 9
 1 Let ’s investigate!

Aim: To model the process of fossil formation.

d
Materials:
 Sand    Fish bone    Water    Salt   Foam cups

Lt
Instructions:
1 Place a cleaned fish bone into a foam cup and fill a quarter of this cup

te
with sand. This is Cup 1.
2 Fill a quarter of another foam cup, Cup 2, with water and salt. Keep stirring

P
and adding salt until no more salt can dissolve. Pour this salt solution
into Cup 1.

on
3 Leave Cup 1 under the hot Sun for a few days. Peel the cup from its contents

when the mixture is dry.

Questions:
1 What do you see after you peel off the cup?

ti
ca
2 Does this experiment model the actual process of fossil formation? Discuss

the similarities and differences with your classmates.

du

Science in context
Wow! The oldest
fossil was found to
E

We found out that be 3.5 billion years

dinosaurs existed old! This means that
millions of years ago Earth is at least 3.5
n

because of their billion years old!

fossils!
to

Fossils can help

us estimate the age
ls

of Earth, known as
geological time. We know
how old a fossil is by looking
A

at its rock minerals and the

depth of the sedimentary
layers where the fossil
)

was found.
(c

Baryonyx
By looking at the features in fossils,
palaeontologists can determine what living
things in the past looked like and even guess
what their diet could be. The snout of the
Baryonyx looks similar to a crocodile's snout.
This suggests that this animal eats fish! Rocks and Soil 127
 Metamorphic rocks
Metamorphic rocks are formed from igneous, sedimentary or other metamorphic
rocks under strong heat and high pressure from Earth’s movement.

d
The rocks are heated but the temperature is not high enough to melt the rocks.
Instead, minerals in these heated rocks go through physical and chemical

Lt
changes. Metamorphic rocks are formed this way. We call this process
metamorphism. No, that is
Look, I am pressing on this
not enough
limestone to apply pressure.

te
Metamorphism pressure and
Will it turn into marble?
sounds like metamorphosis! Do heat to change
you remember what animals this rock!

P
undergo metamorphosis?

on
Heat from magma

ti
Rocks under pressure from Earth
ca
Magma
du

Heat from the magma and high pressure from deep inside Earth
can cause the surrounding rocks to change into metamorphic rocks.

Metamorphic rock without layers Metamorphic rocks with layers

E

Coarse grains Fine grains

Coarse
n

grains
Band Thin and flat
layer
to

Marble Gneiss Slate

Examples of metamorphic rocks

ls

What happens if I heat

Sometimes, the high heat and a mixture of soft candies,
A

pressure can cause layers in biscuits and marshmallows in

the oven and then squash
the rock to curve and bend. them? Does this model the
Hence, we may see wavy bands formation of metamorphic
)

or layers of different coloured rocks?

(c

minerals in a metamorphic rock.

Wavy bands

Metamorphic rocks usually contain tightly packed grains.

So, metamorphic rocks are often hard and non-porous.

128 Chapter 9
 2 Let ’s investigate!

s.
Aim: To identify and classify different types of rock

d
Instructions:

Lt
1 Observe the features of the rocks given to you. Circle.

Are there any layers Are there any

Rock Can you see the grains?

te
or visible bands? fossils inside?
Yes / No Yes / No
A Yes / No

P
It is ( bigger / smaller ) The layers are
than a grain of rice. ( straight / wavy ).

on
Yes / No Yes / No
B It is ( bigger / smaller ) The layers are Yes / No
than a grain of rice. ( straight / wavy ).

ti
Yes / No Yes / No
C It is ( bigger / smaller ) The layers are Yes / No
ca
than a grain of rice. ( straight / wavy ).
du

2 Conduct some tests on the rocks. Circle your observations in the table.
a Scratch each rock with an iron nail to test for hardness.
E

b Drip some water on each rock to test for water permeability.

Rock Can it be scratched? Does water pass through it easily?

n

A Yes / No Yes / No
to

B Yes / No Yes / No
ls

C Yes / No Yes / No
A

3 Sort and group your rocks based on their similarities and differences.
4 Create a classification key to help you identify the type of rocks.
)

You will be given another set of unnamed rocks. Use your classification key
(c

to classify them into groups.

Rocks and Soil 129

 Solve this!

1 Look at each rock below. What type of rock is it likely to be? Describe the
features that helped you to identify the rock type.

d
Lt
___________________ ___________________ ___________________

te
___________________ ___________________ ___________________

P
___________________ ___________________ ___________________
___________________ ___________________ ___________________

on
2 Which rock above most likely contains fossils? How are these fossils formed?

ti
________________________________________________________________
ca
________________________________________________________________
kboo
k
or
Worksheets 1 & 2

W
du

What is the rock cycle?

The formation of sedimentary and metamorphic rocks tells us that one type
E

of rock can undergo changes to become another type of rock.

A rock cycle describes the process of rocks continuously transforming into one
n

of the three types of rock over a long period of time.

to

Scientists use cycles

ls

to explain a repeated Add heat and

pressure The transformation
sequence of events. Do
of rocks in the rock
you remember the water
A

cycle may take up

cycle? What other cycles Limestone Marble to tens of millions of
have you learnt? (Sedimentary rock) (Metamorphic rock)
years!
)
(c

Add heat and

pressure

Sandstone Quartzite
(Sedimentary rock) (Metamorphic rock)

130 Chapter 9
 3 Let ’s investigate!

s involved.
Aim: To model the rock cycle to find out the processe

d
Materials:

Lt
Rock classification key Cups of hot water
10 cm squares of aluminium foil sheets Heavy books
Crayons of different colours  Bunsen burner

te
Grater or oven

P
Why do we need
It is because the
to use a model
rock cycle takes

on
to show the rock
too long to occur!
cycle?

Instructions: ti
ca
1 Grate a few different coloured crayons carefully onto a piece

of aluminium foil. Repeat with other colours to create

du

many layers.
2 Fold the foil to wrap up the layers.
E

3 Press on the foil-wrapped crayon bits as hard as you can.

Then, gently unwrap and observe the substance inside.

n

4 Compare it to the rock classification key you created

earlier.
to

It looks like a/an ( igneous / metamorphic / sedimentary )

crayon rock.
ls

5 Wrap the crayon rock back in the foil. Drop it into a cup of
A

hot water for a few minutes. Then, remove it from the hot
water and press it down with heavy books.
)

6 Repeat Step 5 a few times. Then, gently unwrap the foil once
(c

the crayon rock has cooled down. Observe your crayon rock.
7 Compare it to your rock classification key.
It looks like a/an ( igneous / metamorphic / sedimentary )
crayon rock.
Rocks and Soil 131
 8 Wrap your crayon rock back in aluminium foil.
Heat your crayon rock using a Bunsen burner or
an oven until it melts. Then, remove it from the heat.
Once it has cooled down, gently unwrap it and observe.

d
Compare it to your rock classification key.
9

Lt
It looks like a/an ( igneous / metamorphic / sedimentary )
crayon rock.

te
Questions:
1 What are the processes that took place during the transformation of the

P
crayon rock from one type to another? You may circle more than one.
Melting  Boiling  Solidifying  Rusting  Changing shape

on
2 Draw a diagram to show the transformation of your crayon rock.

ti
ca
du
E
n
to

Conclusion:
ls

In this investigation, different types of rocks can be ( physically / chemically )

A

changed from one type to another. This continuous change is also known as
the r_____ c_____.
)
(c

Think-Pair-Share

In groups, discuss and draw the rock cycle. Include important processes that occur when
rocks change from one type to another. Present your rock cycle to the class.

132 Chapter 9
 Rock cycle

Igneous rocks

d
are formed when Not all rocks are formed by

Lt
magma cools molten rocks from volcanos!
and solidifies. Weathering and erosion Different rock types are
made in different ways.

te
Igneous rock
Deposition

P
Some underground rocks
Solidifying move up to the surface Sedimentation
due to Earth’s movement.

on
and squeezing
Burial, high
temperatures
Magma and pressures

ti
Sedimentary rock

Burial, high temperatures

ca
Melting and pressures

Metamorphic rock
du

Melting
E

When the temperature is high enough, As igneous and sedimentary rocks get
metamorphic and sedimentary rocks buried deeper in Earth, these rocks can
can melt and become magma. The transform into metamorphic rocks through
n

rock cycle repeats. burial, when the lowest layer of rocks is

under high temperatures and pressures.
to
ls

Solve this!
A

Refer to Let's investigate 3 and answer the following questions.

)
(c

Can your igneous or metamorphic crayon rocks be turned into sedimentary

1

crayon rocks? How would you do it?

I would break the crayon rocks down into small pieces like ____________ and
layer them. After the process of _______________, I would press hard on the
layers to form sedimentary crayon rocks.
Rocks and Soil 133
 2 Can your igneous or sedimentary crayon rocks be turned into metamorphic
crayon rocks? How would you do it?
I would apply high ____________ and ____________ to the crayon rocks. After
the process of _______________, metamorphic crayon rocks will be formed.

d
3 Can your metamorphic or sedimentary crayon rocks be turned into igneous

Lt
crayon rocks? How would you do it?
I would ____________ the crayon rocks by applying heat. After a while, the
crayon rocks will ____________ and igneous crayon rocks will be formed.

te
kboo
k
or
Worksheet 3

P
What are the layers of soil under the surface of Earth?
Over many years, igneous, sedimentary and metamorphic rocks become

on
tightly packed in the crust of Earth. They can form a hard solid mass, called
the bedrock.

ti
ca
Humus
Topsoil
Crust
du

Subsoil
Upper
mantle Parent 1.2 m
material
Lower
E

mantle Bedrock
n

Outer core Soil is divided into different

to

layers — Humus, topsoil, subsoil,

Inner core parent material and bedrock.
ls

At the crust layer, rocks can be broken down into smaller pieces by rain, heat,
ice and wind through weathering. Over time, weathering of rocks can form soil.
A

Soil makes up the top layer of Earth’s crust.

Think-Pair-Share
)

Observe the samples of soil given to you. Think about these questions:
(c

What do you know about soil?

Where do we see soil?
What do we usually use it for? Why is soil important to us?

134 Chapter 9
 What is soil made up of?
Soil is generally formed through the breaking down of rocks. Hence, soil can
contain mineral grains like rocks do. Different types of soil are made up of

d
different amounts of sand, silt and clay. This is known as the composition of soil.

Lt
Rice: 8 mm Sand: 2 mm Silt: 0.05 mm Clay: Very small grains

te
Clay, silt and sand are grains of different sizes.

P
We classify soil based on its composition. Different compositions affect the
texture and consistency of the soil. Texture refers to how rough or smooth the

on
soil may feel to touch. Consistency refers to how well the materials in soil are
held together.

4 Let ’s investigate!
ti
ca
Wear gloves when
handling soil since we
Aim: To find out how soil composition do not know what living
things or materials may
du

affects the consistency and texture of soil. be found in soil.

Materials:
E

 Three different dry soil samples labelled A, B and C Water

Gloves   Magnifying glass  Three clear containers
n

with lid
Instructions:
to

1 Observe the colour of each soil sample. Then, use a magnifying glass to

observe any materials or living things found in each sample.

ls

2 a To test for consistency, try to break a small piece of soil sample.

Does it break apart easily?

A

If the soil breaks

easily without pressing, we say it
is loose. If the soil breaks when we
)

press it lightly, it is friable. If we need

to use a large force to break the
(c

soil, then the soil is firm.

Clues Friable – Breaks apart with little force

Rocks and Soil 135

 b To test for texture, place the soil sample on your palm and add a few
drops of water. Then, rub the moist soil with your fingers.
c Take more of each soil sample. Add a few drops of water to each.
Try to mould each one into a ball.

d
Lt
Can all the samples be If the soil feels
rolled into a ball? Does gritty, it has a grainy
the ball break easily? texture. If the soil feels

te
Does it feel sticky? powdery and smooth, it
has a silky texture. If the
soil feels gummy, it has

P
a sticky texture.

on
3 Record your observations in the table. Circle.
Can it be rolled Does the ball
Sample Consistency Texture

ti
into a ball? feel sticky?
Loose / Friable / Grainy / Silky /
A Yes / No Yes / No
ca
Firm Sticky

Loose / Friable / Grainy / Silky /

B Yes / No Yes / No
Firm Sticky
du

Loose / Friable / Grainy / Silky /

C Yes / No Yes / No
Firm Sticky
E

4 Now, let’s find out the composition of each soil sample.

a Fill a clear container with each soil sample and water. Cover each
n

container with a lid and shake the container. Leave the containers to
to

rest on the table for a day.

b In the table below, predict and draw what you might see in each
ls

container the next day.

A

Sample A Sample B Sample C

I predict Result I predict Result I predict Result
)
(c

136 Chapter 9
 Draw and record what you see in each container the next day in the
c

same table.
Measure the height of the different layers of soil and label. What do you
see floating at the top of each container?

d
Questions:

Lt
What is the consistency and texture of each soil sample? Based on these
properties, what do you think makes up each soil sample? Circle.

te
Soil sample A is ( loose / friable / firm ) and ( grainy / silky / sticky ). It is likely to
have the most amount of ( sand / clay / silt ).

P
 oil sample B is ( loose / friable / firm ) and ( grainy / silky / sticky ). It is likely to
S
have the most amount of ( sand / clay / silt ).

on
Soil sample C is ( loose / friable / firm ) and ( grainy / silky / sticky ). It is likely to
have the most amount of ( sand / clay / silt ).

ti
ca
Decreasing size
du

Sand has the biggest

grain size while clay has
the smallest grain size.
E
n
to

Sand Silt Clay

Grain size of different soil minerals

ls

What will happen

A

if we pour water through these

grains? Which one will let water
pass through easily? Which one
)

can hold more water?

(c

Think-Pair-Share

Which type of mineral grains do you think holds water well? Clay, silt or sand? Why do you say so?

Rocks and Soil 137

 What are the different types of soil?
When we add water to the soil, the different materials in the soil settle into
different layers. The smaller grains are lighter so they float in water. The
bigger grains are heavier so they sink to the bottom. This allows us to see the

d
composition of each type of soil.

Lt
Sandy soil Loamy soil Clay soil

te
Humus Humus Humus
Clay Clay Clay
Silt Silt Silt

P
Sand Sand Sand

on
Sandy soil contains a large Loamy soil is a good Clay soil contains more
amount of sand. Sand has mixture of sand, clay and clay. When wet, clay soil is
a bigger grain size. So, this silt. It is a little grainy but very sticky. When dry, it is
type of soil has a grainy can be silky and slightly firm and hard as concrete.
texture and does not hold sticky. This is good for Clay soil is not suitable for

ti
water as well as the rest. growing plants as loamy most plants as the roots
This soil also breaks apart soil is friable and roots can are unable to push through
ca
easily. We say that sandy push through the soil to get the firm clay to get water
soil is loose. water and nutrients. and nutrients.
du

Humus
When living things die, they are Notice what
is the lightest and floats
E

usually broken down through the at the top? These

process of decaying. When they are the organic
materials.
are broken down, organic materials
n

are formed. We call these organic

to

materials humus. Humus usually Small creatures

forms the top layer of soil. like earthworms help
to break down living
ls

Organic materials contain nutrients things that are dead

into useful minerals
that help plants grow well. If the soil and nutrients in the
A

contains lots of nutrients for plants humus layer.

to grow well, we say the soil is fertile.

)

So, we can tell how fertile the soil is by

We may find
looking at the humus layer of the soil.
(c

decaying leaves
or dead animals
Loamy soil contains a large amount in humus.
of humus which provides nutrients
for growing plants.
kboo
k
or
Worksheet 4
W

138 Chapter 9
 Are all soils good for growing plants?
Soil is very important to us. We use it to grow most of our crops.

Soil stores water Can we use any soil to

d
and nutrients for grow plants? Are all the
plants to grow. soils the same?

Lt
5 Let ’s investigate!

te
growing tomato plants.
Aim: To find out which soil type is the most ideal for

P
Materials:
What can we check

on
 Loamy soil  Clay soil  Tomato seeds to see if the plant is
 Sandy soil  Containers  Water growing well?

Instructions:

ti
1 Plan an experiment to find out which soil sample is the best for
ca
growing a tomato plant.
Use the following questions to guide you in your plan.
2
du

What are the independent variable and dependent variable?

 ____________________________________________________________

Which variables should be kept constant?

E

 ____________________________________________________________
n

3 Monitor the growth of your plants over two weeks. Record your
observations in the table below. We can put
to

our dependent
variable here.
We can put our
ls

independent
variable here.
A
)
(c

Question:
Which soil sample is the best for plant growth? Why?
________________________________________________________________
________________________________________________________________
Rocks and Soil 139
 Clay soil is not good for
most plants as there is not
There is no perfect enough oxygen inside the
soil. Different plants soil for the roots. This can

d
grow best in different cause the roots to rot.
soil types.

Lt
te
P
on
ti
ca
Sandy soil cannot hold water well Clay soil can hold water well, making
du

and allows water to pass through it it sticky. This type of soil is suitable for
easily. So, this type of soil is suitable for plants that need a lot of water such
growing plants that do not require a lot as rice crops.
E

of water such as cacti and palm trees.

n

Solve this!
to

1 Identify the type of soil in each jar.

ls

Clay
A

Silt
Sand
)
(c

Clues Rot – To become decayed or weakened, usually by the action of bacteria or fungi

140 Chapter 9
 Minerals and organic materials in the soil are
I rotate my crops
every year so that the used up by plants. This can change the soil
nutrients in the soil have time composition. So, when crops are repeatedly
to replace themselves. I can grown through activities such as gardening

d
also change the composition
of the soil by adding fertilisers. and farming, the composition of soil changes

Lt
This will make the soil over time.
more suitable for Fertilisers contain
plant growth. Fertilisers also decomposing plants and
contain important faeces of animals. These

te
minerals like help to increase the amount
nitrogen to help of organic materials in
plants grow well! the soil!

P
on
ti
ca
du

Loamy soil holds enough water and allows roots

Watch to find
to push into the soil to obtain water and nutrients. out more about
This type of soil is suitable for growing most
E

how human
activity can affect
garden plants like vegetables. the quality of soil.
n

Vera uses two different types of soil to grow her rose plants, Soil A and B.
to

She waters her rose plants every morning before going to school. When she
returns in the evening, Soil A feels wet and sticky to touch, while Soil B feels
ls

slightly moist. A few weeks later, she observes that the rose plant growing in
Soil A is dying.
A

Which types of soil does Vera have?

a

Soil A: ____________________     Soil B: ____________________

)
(c

b After growing the rose plant in the same pot of Soil B for many months,

Vera noticed that the rose plant is dying now. What could have caused
the rose plant to die?___________________________________________
kboo
k
or
Worksheet 5
W

Rocks and Soil 141

 Crack the case

undergo weathering to form

Rocks

d
can be
classified into

Lt
te
Under high
temperature and

P
__________
Igneous Sedimentary Metamorphic

on
rocks rocks rocks

ti Erosion and
sedimentation
ca
Erosion and
sedimentation
may
du

contain
melts to
form
melts to
solidifies
E

form
to form Magma
n
to

can be used Fossils

to measure
ls
A

__________ time
)
(c

142 Chapter 9
 consists of
Soil Different layers

with

d
Humus
Topsoil

Lt
Different composition Subsoil
Parent
material
Bedrock

te
Sandy soil Clay soil Loamy soil

P
Humus Humus Humus
Clay Clay Clay
Silt Silt Silt

on
Sand Sand Sand
Also contains a
high amount of

ti
__________ that
Consistency: Consistency: Consistency: is important for
ca
__________ __________ __________ plant growth
Texture: Texture: Texture:
du

__________ __________ __________

over time
E

______________ of soil can change which can affect plant growth

n
to

? Tick ( ).
ls

What can Tim and Vera do

ts.
into his pot to grow his plan
Tim can add clay and silt
A

im can ad d clay into his pot to grow his plants.

T
.
d m or e sa nd int o his pot to grow his plants
)

Tim ca n ad
ck ins tead to loosen the soil.
(c

Vera ca n use a gr an ite ro

n us e a lim es to ne rock instead to loosen the soil.

Vera ca
kboo
k
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Consolidation worksheet
W

Rocks and Soil 143

 CHAPTER 10 Food Webs
The children are participatin
g in a school project and are
grasshoppers and a frog. Th given a tank with plants,
ey have to add another anim
al to the tank and ensure

d
that this animal can still survi
ve after five days.

Lt
Grass
hopp
er
Spid
er

te
Fro
Snai g
l
Fun fac
Bass ca t:

P
n only
survive
in
water th Plants
at is
3-metre

on
deep!

Turtle Bass

ti
Where should
we place our tank?
There is no school
ca
for the next five
days, we will not be
able to feed them!
du
E

We should
n

make sure that this

animal that we add
to

will not be eaten up

by the others.
ls

What do the
living things in
What Will I Learn
A

the tank need to

survive?
Interpret feeding relationships in food webs and identify the
food chains within them. What is the source
)

of energy for the

Describe how toxic substances can move through a food
(c

living things in
chain or food web.
the tank?
Identify the energy source of a food chain or food web. Which living
Describe how energy is transferred through a food chain or thing in the tank
food web. is a prey? Which
is a predator?
144 Chapter 10
 How do food webs show interactions in an ecosystem?
Living things found in a specific environment
Retrace our steps
interact with other living things and their
surrounding environment. What are food

d
chains? What are
Living things depend on other living things for some types of living

Lt
survival. They can also be affected by non-living things found in a
food chain?
factors in their environment such as air, water
and temperature.

te
An ecosystem consists of all the living and non-living things that exist
and interact with one another in the same environment.

P
Think-Pair-Share

on
1 We have learnt to use food chains to show feeding relationships between
living things. Using the Internet or books, research a simple food chain you can find
in a garden.
Draw a food chain that you have found. Label the living things with the following

ti
2

helping words:
ca
We can describe the feeding relationships between living things
du

using a food web. A food web is made up of many food chains in an

ecosystem.
Similar to a food chain, a food web always starts with a producer.
E

A producer is a living thing that carries out a process called

photosynthesis to make food in the form of sugar.
n
to

Sunlight
Carbon Sunlight
+ Water Sugar + Oxygen
dioxide
Chlorophyll
ls

Oxygen
A

Carbon dioxide
)

Photosynthesis takes place Water

(c

inside the leaves of plants

Photosynthesis – A process by which plants use sunlight, carbon dioxide and

Clues water with the help of chlorophyll to make food and produce
oxygen

Food Webs 145

 Similar to a food chain, a food web also ends with a consumer. A consumer
feeds on plants or animals or both for energy.
Here is an example of a simple food chain, where the grass is the producer and
the animals are the consumers. There are different types of consumers.

d
Lt
Producer Consumers

A primary consumer A consumer that A consumer that

te
feeds on producers. feeds on a primary feeds on a secondary
It is also the first consumer is called a consumer is called a
consumer found secondary consumer. tertiary consumer.
in the food chain.

P
on
ti
Grasshoppers are herbivores. Frogs and hawks are carnivores.
A consumer that only feeds A carnivore is a consumer that
ca
on plants is called a herbivore. only feeds on other animals.

An omnivore is a
Momo is an omnivore.
consumer that feeds on
du

He feeds on small
both plants and
insects and plants
animals.
parts!
Look at the food chain
E

above. Who is the prey

and who is the predator?
Can you label them?
n
to

What about me?

Which type of
consumer am I? Prey
Predato
ls

r
A

A predator is an
animal that hunts and eats
other animals. A prey is an
animal that gets eaten by
)

the predator.
(c

146 Chapter 10
 1 Let ’s investigate!

are connected
Aim: To model how living things in an ocean habitat
in a food web.

d
Materials:

Lt
Plant and animal cards from the ocean habitat
Strings

te
Arrow cards

Instructions:

P
1 Read the information about the plant or animal on the card given to you.

This will be your role. Are you a producer or consumer?

on
I am a ( producer / consumer ) because I ___________________________.
2 Describe the feeding relationship between you and your classmates.

ti
a Is your classmate a producer? Do you feed on producers?

b Is your classmate your prey?

ca
c Is your classmate your predator?

Use a string to connect yourself to your classmates to form a food chain.

du

Paste an arrow on the string to represent the feeding relationships

between you and your classmates.
3 Find more classmates so that your food chain shares a consumer or
E

producer with another food chain in your class. You have now formed a
food web!
n

4 Draw the food web formed by your class!

to

In a food The sea lion

chain, energy is eats both crabs
and small fishes!
ls

transferred from
the crab and small
fish to the sea
A

lion. The arrows

point towards the
sea lion!
)

We use If an animal feeds on

(c

arrows to show more than one type

how energy is of living thing, you can
transferred from form multiple links to
one living thing to the card.
another.

Food Webs 147

 Can you think of more
Questions: producers or consumers
to add to the food web
Using the food web formed by your class: that you have drawn?
1 How many food chains can you find?

d
2 What is the longest possible food chain you can identify?

Lt
3 Identify the producers in the food web. What will happen
if all the producers are removed from the food web?

te
P
on
What are you
eating for lunch

ti
today? I am eating seafood
soup! It has shrimps,
mussels, clams and kelp.
ca
Wow! I can form
du

a food web with the

living things around us,
including the ingredients
in our food that were
E

once alive.
n
to

Human
ls

Clam
A

Mussel Kelp
)

Shrimp
(c

Plankton Simple food web

Plankton – Very small plants or animals that are found in water and often
Clues become food for other aquatic animals

148 Chapter 10
 The arrow
represents 'eaten
by'. This means the Sea
clam is eaten by Sea otter bird
Crab How many types of
the sea otter.

d
predators does the
mussel have?

Lt
Clam
Rock

te
Shrimp snail

Plankton

P
Mussel

on
A food web may look complex because it links several food chains together.
We say that the feeding relationships in a food web are interconnected.

Most living things are eaten by more than one other living thing in the
ecosystem.
ti
ca
From this food web, we can see that each living thing can have different types
of predators feeding on them:
 In this habitat, rock snails only have one type of predator — sea birds. There is
du

only one arrow pointing from rock snails to their predators.

 Clams, shrimps and mussels have two types of It has not
predators. There are two arrows pointing away
E

rained for many days.

from each of them. Corn plants in this field
are all dying. What will
n

happen to the other

The living things in a food web are interdependent. living things in this
to

When the number of one living thing drops, it will habitat?

affect the number of its prey, predators, or both.

This can then affect the number of other living
ls

things in the food web.

A

If the amount of food decreases, consumers will have less food to eat. Some
consumers may die due to the shortage of food. Other consumers may
)

depend heavily on another food source, affecting the number of other living
(c

things in another food chain.

Interconnect – To connect two or more things together

Clues Interdependent – To depend on each other

Food Webs 149

 What happens if the amount of corn decreases?

Frogs and rats will

Amount of corn Number of have to find other food
decreases grasshoppers sources to feed on. If
decreases not, they may die.

d
Number of rats
decreases

Lt
te
Number of frogs decreases

P
If the amount of corn
decreases, there is less food
for the grasshoppers to eat.

on
This may cause the number of
grasshoppers in the food web
to decrease too.

Solve this!

ti
ca
In the food web below, identify three food chains with at least three living things in
each of them.
du

Hawk Chicken

Frog
E

Lizard
n
to

Grasshopper Slug
ls

Grass
A

1 ________________________________________________________________
)
(c

2 ________________________________________________________________

3 ________________________________________________________________
kboo
k
or
Worksheet 1
W

150 Chapter 10
 Retrace our steps
How does energy flow in a food web?
What is the main
source of energy of
Eagle
a food chain? How is
energy transferred

d
1  The Sun provides the between the different
main source of energy living things?
to food chains.

Lt
5  When tertiary consumers
eat secondary consumers,
some energy is transferred.

te
4  When secondary consumers

P
Snake eat primary consumers, some
Plants do not get their
energy is transferred.
food from the soil, but
they obtain water and

on
minerals from the soil 3  When primary consumers eat
for growth. producers, some energy is
transferred to the consumer.
Rabbit

ti
Grasshopper

 Energy from the Can you identify the

ca
2

Sun is taken in Grass

primary, secondary and
and converted tertiary consumers in this
into food by food web?
du

producers
through
photosynthesis.
Producers
E

then store the

energy in their
plant parts.
n
to

Where do living
After energy is transferred from one living things get the
ls

energy they need

thing to another, the consumer uses some to survive?
of this energy to move, while some of the
A

energy is lost to the environment as heat.

So, not all energy will be transferred to
the next consumer in the food web. Most
)

of the time, only about 10% of energy is

(c

transferred to the next consumer.

The way energy passes through an
ecosystem is described as energy flow.

Food Webs 151

 2 Let ’s investigate!

chain or food web.

Aim: To model how energy is transferred in a food

d
Materials: Retrace our steps

Lt
Balls that represent energy What process
do plants undergo
Baskets that represent plants in order to take
Role cards for rabbits, snakes and eagles in energy from

te
the Sun?
Instructions:
1 The class will be divided into three groups — rabbits, snakes and eagles

P
depending on the card you receive. You will be representing these animals
in the food chain shown below:

on
Plant ➞ Rabbit ➞ Snake ➞ Eagle
2 Your teacher will be the Sun, who has all the energy balls.

ti
3 There will be baskets placed at different corners of the classrooms to act
as plants. Your teacher will transfer the energy balls into the baskets.
ca
This means the plants now have ________ from the Sun to make ________.
4 Round 1: Depending on the card you get, you can now 'feed on' other
du

living things by taking energy balls from them. Do you take all the energy
balls from them? Round 1 ends when there are no more energy balls in
the basket.
E

5 Your teacher will reset the game by collecting all the balls and putting them
in the baskets.
n

6  ound 2: In this round, all the rabbits are dead. All the students representing
R
to

rabbits will sit down. Other students will continue to play the game. Can
the energy balls be transferred from the basket to other consumers in the
ls

food chain?
7 Your teacher will reset the game again.
A

Round 3: In this round, there is no Sun. Your teacher will not put any balls in
8

the baskets. What happens to the living things in the food chain?
)

Questions:
(c

1 When you were eaten by a consumer, did you pass all the energy balls to

your consumer? Why or why not?

________________________________________________________________
________________________________________________________________
152 Chapter 10
 2 Refer to Round 1. What happens after all the plants are eaten up?
________________________________________________________________
________________________________________________________________

d
3 Refer to Round 2. What happens if all the rabbits die? What does this tell you

Lt
about the food chain if all the rabbits are missing from the food chain?
________________________________________________________________
________________________________________________________________

te
4 Refer to Round 3. What happens if there is no Sun? What happens if the

Sun’s energy cannot reach Earth and the plants?

P
________________________________________________________________

on
________________________________________________________________
5 What can you say about the number of energy balls carried by the students
representing eagles and the number of energy balls your teacher placed in

ti
the plant baskets at the start of the round?
ca
________________________________________________________________

The Sun is our main energy source. Energy

du

Do you know that

from the Sun is needed so that energy can if the Sun stops giving
flow in the food web from the producers to out light energy, living
things will not be able
the consumers.
E

to survive on Earth?

Solve this!
n

1 What is the main source of energy in an ecosystem?

to

2 Using the clues below, draw a diagram to represent how energy may flow
through the following living things in an ecosystem:
ls

Raccoon  Grasshopper  Owl  Plant  Snake  Sun
The grasshopper is a herbivore.
A

The raccoon feeds on plant parts and grasshoppers.

The owl feeds on raccoons and grasshoppers.
)

The snake feeds on owls and raccoons.

(c

3 What is the amount of energy that may be transferred from the producer

to the primary and secondary consumers? Circle.

Grass Rabbit Fox
100 units of 120 units / 80units / Worksheet 2
or
kboo
k
W

energy 100 units / 10 units /

10 units 1 unit Food Webs 153
 Science in context

How do human activities impact the ecosystem?

Humans are part of the ecosystem and we depend on living and non-living

d
things around us for survival. The way we interact with the ecosystem will

Lt
affect other living things and our activities may have a positive or negative
impact on the ecosystem.

Negative impacts on ecosystem

te
Humans may introduce changes to the environment in many negative ways —
pollution, overhunting, deforestation and introducing the wrong types of living

P
things to an area.

on
ti
ca
Some farmers may burn plants Introducing the wrong types of Excessive whale hunting may
du

to clear land quickly for farming. plants or animals to an area may cause its kind to become
This can produce a lot of air disrupt the food web. endangered or extinct.
pollutants, contributing to air
Cane toads that were introduced Overhunting causes some
pollution and global warming.
into Australia do not have natural types of animals to die faster
E

Many lives of animals and plants predators there. They also feed on than they can reproduce. This
are lost. a lot of animals and reproduce very can affect the number of prey
quickly. As such, this can negatively and predators in the food web.
affect the number of prey and
n

Deforestation occurs predators in the food web.

when trees are cut down
to

faster than they are We burn fossil

replanted. Deforestation fuels to power
can cause many animals machines that When we rear
help us in farming farm animals,
ls

to lose their habitats and

food sources. As a result, such as growing these animals may
many animals may die. plants for food compete with other
A

production. Using living things in the Poachers are

more machines natural habitat for people who illegally
releases more food. Over time, living hunt and kill animals,
greenhouse gases things in the natural which upsets the
)

into the air which habitat may not ecosystem.

contributes to have enough food to
(c

global warming. survive.

154 Chapter 10
 Positive impacts on ecosystem
We can create parks and natural reserves to protect some types of animals
and plants from extinction.

d
Lt
te
P
The David Sheldrick Wildlife The Tiritiri Matangi Open The Kruger National Park in
Trust in Kenya shelters Sanctuary in New Zealand South Africa protects animals
orphaned elephants. protects endangered reptiles from overhunting.

on
and birds like this takahe.

We can also find ways to reduce the negative impacts of our activities and
restore the environment.

Oil booms prevent oil from

ti
Skimmers are machines that remove
ca
further spreading in the ocean. oil from the water surface.
du
E
n

Technology can help us design machines and find new ways to

We can replant trees
to

reduce the impact of pollution. Equipment such as oil booms and

in areas affected by
skimmers help us to clean up an oil spill.
deforestation. This process
is called reforestation.
ls

Ecologists use science to

understand the relationships between
A

plants, animals and their environment

to better protect them.

Overusing land Pollutants enter

)

for growing crops rivers, seas and oceans,

(c

causes soil erosion. affecting the food web. Wildlife

Sanctuary
Parks
Reforestation

Food Webs 155

 How do harmful substances affect living things in the food web?

Factories and human activities like mining, spraying pesticides and littering can
release toxic substances into the ecosystem. These toxic substances can move
through a food web and harm living things, resulting in illnesses and even death.

d
Traces of heavy metals Lead from old water Mercury used to paint ship

Lt
such as mercury, lead and pipes can also leak into hulls can enter the waters.
arsenic from mining may flow nearby water bodies.
into seas and oceans.

te
P
on
Pesticides may
contain harmful substances
such as mercury and DDT. 280 million tonnes

ti
When crops are sprayed with of plastic enters the
these pesticides, the substances oceans every year.
ca
can contaminate the soil. Crops
can take in these toxic substances.
du

Toxic substances such

as heavy metals and
E

microplastics may enter

Crops
planktons in the water.
When we dump litter into
n

oceans, plastic waste can

When humans break down into microplastics.
consume crops
to

Microplastics can stay in the

and chickens, high ocean for a long time as they take
amounts of toxic very long to break down.
substances are
ls

passed on to them.

Chicken feed
A

contains a
small amount
of arsenic
Another common toxic
)

for muscle
growth in substance found in the
(c

chickens. food chains is cadmium.

Research to find out where this
When chickens consume more substance comes from and
chicken feed, arsenic increases in how it can affect living things
amount in the chicken’s body.
in a food chain.

156 Chapter 10
 Most living things can survive with a very, very small amount of toxic substance in
their bodies. These substances can become harmful if they are present in large
amounts in living things. The process where toxic substances increase in amount in
the body of a living thing is known as bioaccumulation.

d
Toxic substances in living things can also be transferred from one living thing

Lt
to another in a food chain or food web. Toxic substances can build up in the
consumers in the food chain over time. As such, consumers higher up in the food
chain are usually the most affected.

te
When humans and whales consume these sea creatures, they ingest
a large amount of the toxic substances.

P
on
ti
When shrimps eat Toxic substances
plankton, the toxic such as heavy metals
substances enter and microplastics are
ca
the shrimp's body. collected in shellfish
Shrimps retain the when they filter them
toxic substances in out from the ocean.
their bodies.
du
E

Toxic substances
get passed on
into the bodies of
consumers that
n

feed on shrimps.
to

The ingested microplastics may The amount of

block the digestive systems of toxic substances
ls

consumers. collected in each

animal greatly
increases higher
A

in the food chain.

)

Watch this video to learn about how

(c

toxic substances affect living things in Heavy metals Microplastics

a food chain.
Toxic substances – Harmful materials that can cause living things to become sick,
Clues poisoned or die when absorbed
Ingest – To swallow and absorb

Food Webs 157

 In this model,
each red dot represents
1 unit of a toxic substance. This gets worse!
When the shrimp eats Tuna When the tuna eats four
two krill, it accumulates shrimps, it accumulates
2 units of the toxic 8 units of the toxic
substance. substance.

d
Lt
Shrimp

te
Krill

P
The amount of toxic substances increases higher
up in the food chain. The concentration of the toxic
substance increases as predators eat more prey.

on
Think-Pair-Share

Let's use a physical model to show the effect of toxic substances

ti
in a food chain. You and your classmates will role-play living things
in a food chain. Students role-playing plants will be given blocks
ca
that represent toxic substances. What happens to the toxic
substances when herbivores eat these plants? What happens to
the toxic substances when other animals eat these herbivores?
du

Solve this!
E

Complete the passage with the following helping words.

n

Bioaccumulation   Concentration   Living thing
Ingest   Illnesses   Toxic
to

________________ is the process where ________________ substances

ls

increase in amount and build up in the body of a ________________.

A

Consumers feeding on producers or prey affected by these harmful

substances will ________________ these substances. If the substance
)

accumulates to a high ________________ in a living thing, this may cause

(c

________________ or even death. k

kboo
or
Worksheet 3
W

Clues Concentration – Amount of substance per unit volume

158 Chapter 10
 Describes the
Crack the case _____________ between
Food Web living things and shows
how energy is transferred
is made up

d
of many
Mountain lion interconnected ____________

Lt
Lettuce ➞ Rabbit ➞ Fox ➞ Mountain lion
Lettuce ➞ Squirrel ➞ Fox ➞ Mountain lion

te
Fox

Primary Secondary Tertiary

P
Producer consumer consumer
consumer
Squirrel

on
Rabbit

Carries out ___________  Herbivores, _________

to make its own food using and _________

ti
energy from the ______ Prey and _________
Lettuce
ca
when toxic substances Toxic substances can be _________ or
enter a food chain or web transferred from one living can ________ if the
thing to another and build up cause ______________ of
du

Bioaccumulation in the consumers over time the toxic substance

occurs is high enough
E

to their tank? Tick ( ).

n

ou ld th e ch ild re n ad d
Which animal sh
it ca n fe ed on th e gr asshoppers in the tank.
as
to

 hey should add a spider

T
a sn ai l as it ca n fe ed on the plants in the tank.
 hey should add
T
e plants and frog in the
ls

tu rtle as it ca n fe ed on th
 hey should add a
T
n feed on the turtle.
tank. No other animals ca
A

as it ca n fe ed on the frog in the tank. No other

 hey should add a bass
T
ss.
animals can feed on the ba
)

their tank? Tick ( ).

Where should they place
(c

ta nk in a plac e wi th su nlight so that the plants

 hey should place their
T
esis.
can carry out photosynth s have
ac e th eir ta nk in a sh ad y place so that the animal
 hey should pl
T
a cooler place to sleep.
kboo
k
or
Consolidation worksheet
W

Food Webs 159

 CHAPTER 11 Growing Up and Pubert
y
The children were enjoying lun
ch together. When they finish
stains on her pants and left ed, Vera noticed some

d
the room in a hurry. What ad
Vera's friends to care for he vice would you give to
r?

Lt
I will go and
check on her! Where is Vera

te
going?

P
I do not feel so well.
Please excuse me,
I need to go to the

on
bathroom.

ti
ca
Did Vera sit on
spilled ketchup?
du

Does she need

help?
E
n
to
ls
A

What Will I Learn

Name the parts of the reproductive system in humans.
)

Describe puberty in humans and the physical changes that occur

(c

What are some What caused the What would Ve

physical changes th stains on Vera's ra
at need during th
can occur in girls an pants? What is she is
d time?
boys during puberty? experiencing now?
160 Chapter 11
 What is puberty?
Growing up is a natural part of life's process. After reaching a certain
age, living things, including humans, can start to reproduce.

d
Puberty is a part of our life cycle. It is a period where our body matures
and becomes ready for reproduction. During puberty, our reproductive

Lt
organs mature. We also grow quickly and experience changes in
our body.
Girls may begin puberty earlier than

te
boys. Puberty in girls usually takes
place between ages of 8 and 13.

P
Puberty in boys commonly occurs
between ages of 9 and 14.

on
The age when puberty begins
is different for everyone. Puberty
usually starts between the age of 8

ti
to 14.
ca
The following day, the children were visiting Vera's baby cousin...

When our reproductive organs

du

How does the

mature, we are able to reproduce body know when
and have babies. Biologically, we are to start developing
maturing and becoming an adult as the reproductive
part of the human life cycle. Growing into an adult also
E

organs?
involves maturing into a
person with responsibilities.
n
to
ls
A

In different countries, the legal It depends on our brain!

)

age to be known as an 'adult' is The brain releases a substance

(c

different too. A child growing and called a hormone, which tells

developing into an adult is called parts of the body to start the
an adolescent. It usually happens development process.
between the ages of 10 to 19.

Growing Up and Puberty 161

 What are the changes that occur during puberty?

Wow, she has This is my mummy when

changed so much! she was 7 years old.

d
Lt
te
Think-Pair-Share

P
Recall what you used to like when you were about 7 years old. Draw a portrait of yourself then
and one of yourself now.

on
Then, think about what you liked before and what you like now.
What are some changes you noticed? Discuss. I used to like
I used to like listening to play soccer.
At 7 years old Now to music. Now, I still like Now, I like

ti
to listen to music but I basketball!
Hobbies enjoy dancing too!
ca
Favourite sports

Favourite music
du

Favourite show
E

Recently, my skin has

My voice is starting
n

become so oily that I Increase in

to change. How height (cm/year) 10 Boys
have to use this special
about yours?
to

Girls
cleanser to keep my
8
face clean and fresh!
What did you notice
6
about your height? Did
ls

you know that the bones

in your arms and legs 4
A

become longer during

puberty? 2
)

0
8 9 10 11 12 13 14 15 16 17 18
(c

Age (years)

Referring to the graph,

what can you say about the
relationship between the
increase in height and age?
Discuss.

162 Chapter 11
 Physical changes in our body
Our bodies undergo many physical changes during puberty. Some changes
happen in boys and girls. Some changes only occur in boys while others only
occur in girls.

d
In boys In both boys and girls In girls

Lt
Facial hair The skin produces
develops on the an oily substance that
jaw and above the can cause one to smell
mouth. bad if it is not washed
Breasts develop and
off regularly. It may
become bigger to be
also block skin pores,
ready to provide milk

te
Voice breaks and causing pimples or
deepens suddenly or for a baby after giving
spots to develop.
over a long period. birth.

Hair develops under

P
the armpits and around
Shoulders become Menstruation starts.
the pubic area.
broader. Boys may develop
longer and more

on
noticeable hairs Hips become wider.
Muscles develop on their arms, legs
all over the body and and chest.
strength increases. Hair growth can happen
very differently in
different people.

ti
Testes and penis
become bigger. Both boys and girls
will experience a period
ca
of rapid growth where
they grow taller and
become heavier. This is
called a growth spurt.
du

Watch this video to learn more

about changes during puberty.
Solve this!
E

List and describe some physical changes that boys and girls may experience
during puberty. Group the physical changes into the Venn diagram below.
n

Physical changes
Physical changes Physical changes in both in girls
to

in boys
ls
A
)
(c

kboo
k
or
Worksheet 1
W

Pubic area – A region near the reproductive organs on the outside of the body
Clues Growth spurt - Short period of time where a person experiences quick growth in height
and weight

Growing Up and Puberty 163

 What are the organs in our reproductive system?

The human reproductive system is made up of a group of organs working

together to help us reproduce. The reproductive organs are different in males
and females.

d
Female reproductive system

Lt
Several organs make up the female reproductive system. These reproductive
organs are inside the female body.

te
Oviduct Uterus

P
The oviduct is a narrow tube The uterus is a hollow and
that extends from the ovary muscular organ. This is where
to the uterus. The egg travels the baby develops and grows
through this tube to the uterus. when inside the mother's body.

on
ti
ca
Egg
du

Ovary
There are two ovaries in the
female body. Eggs and female
sex hormones are produced
E

here. Eggs are released from

the ovaries when they mature.
Flowering plants
n

have eggs in their ovaries

too! Unlike the eggs in Vagina
to

humans, eggs in flowering The vagina is a muscular and hollow tube that has an
plants stay in the ovary – opening at the end. The male reproductive organ enters
they do not move. the female body through this opening to deposit male
ls

reproductive cells known as sperms. It is also a birth

passage. A fully developed baby leaves the mother’s
body through this passage during natural childbirth.
A

As our bodies go through puberty, our reproductive organs mature and

)

release a group of hormones called sex hormones into our blood.

The amount of sex hormones in our blood increases and changes
(c

differently for males and females. This affects how our bodies change.
This is also why some physical changes only occur in males and some
others in females. Some physical changes occur in both genders.

164 Chapter 11
 Retrace our steps

Male reproductive system What are the body

Unlike the female reproductive system, some of the systems that you have
learnt? Are there any
male reproductive organs are outside the body.

d
differences between
these body systems in

Lt
boys and girls?

te
Sperm duct
The sperm
duct is a long
narrow tube that

P
extends from
the testis to the
penis. Sperms

on
travel to the
penis through
this tube.

ti Penis
The penis is
ca
found outside
the male body.
It is inserted into
du

the female body

through the
vagina to deposit
Testis sperms.
A male has two testes. Each testis
E

is held and protected by a bag of

skin. The testes produce sperms
and male sex hormones. kboo
k
or
Worksheet 2
n

W
to

Apart from being part

The sperms in of the male reproductive
a male body have a similar system, the penis is also
ls

function as the pollen used for passing urine out

grains in the male part of a of the male body.
A

flowering plant.
)
(c

Growing Up and Puberty 165

 Menstrual cycle in females
A female experiences menstruation during puberty. The start of
The fertilisation
menstruation signals that the body is capable of reproduction process is similar

d
where a female could become pregnant with a baby. to how the pollen
grain fertilises

Lt
To prepare for pregnancy, the body undergoes the menstrual the egg in the
cycle which usually takes place for around 28 days. ovary of a
flower.

te
Egg Oviduct

During each

P
menstrual cycle, a
matured egg will
be released from
one of the ovaries.
Egg

on
The egg travels Ovary
through the The lining of the
oviduct. If the egg uterus is filled with
meets a sperm blood vessels. The
here, fertilisation lining thickens
Lining of

ti
will occur. along the muscular
the uterus walls of the uterus.
It prepares to
ca
If the egg is fertilised, it will support the
travel to the uterus and growth of a baby if
Menstruation commonly lasts for 3 to 7 days. become attached to the fertilisation occurs.
After this, bloody discharge from the vagina lining of the uterus. The
stops. The uterus starts to repair itself. female becomes pregnant
du

In the ovaries, another egg starts to mature. The and the cycle stops here.
cycle repeats.
If the egg does not meet a
sperm, fertilisation does not
occur. The unfertilised egg
Egg
E

dies. The female body will

get rid of the unfertilised egg.
The lining of the uterus will
also be removed or shed. The
unfertilised egg and lining of
n

the uterus will be discharged

through the vagina. This
to

process is menstruation and it

occurs once in around 28 days.

Vagina Find out about the

physical and mental
ls

Why is there a changes that may occur

need to remove when menstruation begins.
A

the unfertilised egg

and the lining of the An unfertilised egg can
uterus? cause health problems
if it remains in the body.
)

Menstruation helps the

body to avoid these.
(c

Pregnant – Having a baby developing inside the female body

Clues
Fertilisation – An egg joining a sperm in the female reproductive system to grow into an offspring
Discharge – To remove by passing out or releasing

166 Chapter 11
 Everyone grows and This is a sanitary pad.
matures at different rates. For It helps to absorb the
girls, do not worry if you do not What is this? bloody discharge during
start to menstruate at the menstruation. It keeps me

d
same time as others! clean and hygienic.

Lt
te
P
on
Do you know? In some
places, people refer to the
process of menstruation as

ti
'getting a period'.
Science in context
ca
In order to have young, our reproductive systems need to be healthy.
du

If there are problems with our reproductive system, we can look for doctors
who specialise in reproductive systems.
E

I am a gynaecologist.
I look after the health of the female
reproductive system. I am also an
n

obstetrician! I give advice and care to

women during pregnancy, delivery
to

and after childbirth.

De
Ob partm
Gy stetri ent
ls

nae cs of
col and
ogy For girls, we can look for
I am an andrologist. a gynaecologist if we
I manage the health of experience any menstruation
A

the male reproductive issues during puberty.

system.
)

y
log
(c

dro
of An
ent
rtm
pa
De

For boys, we can look

for an andrologist.

Growing Up and Puberty 167

 Solve this!

1 Match each organ in the human reproductive system to its function.

d
The egg moves through this
Ovary
tube to get to the uterus

Lt
An opening from which the
Oviduct lining of the uterus and the
unfertilised egg are discharged

te
Where sperms are
Penis

P
produced

Where a baby grows

on
Sperm duct
and develops

Where eggs are

Testis
ti produced and mature
ca
From which urine is removed
Uterus
and sperms are released
du

Sperms move through this

Vagina
tube to get to the penis
E

Classify the reproductive organs above into male and female organs.
n

2
to

Reproductive organs in male Reproductive organs in female

ls
A
)
(c

kboo
k
or
Worksheet 3
168 Chapter 11
W
 Crack the case
Reproductive System It is a period in
our life cycle
is made up of where our
Male body matures
Reproductive organs and becomes

d
Sperm ready for
duct

Lt
mature during reproduction.

Puberty

te
cause physical
changes in
Males Females

P
______ ______  ________ develops on
1. _ 1. Hips _________
jaw and above the mouth

on
2. _ ________ develop
 ________ develop all
2. _ and become bigger
over the body 3. ______________
Female

ti
Oviduct 3. S houlders become starts where
_________ unfertilised egg
ca
4. Voice _________ and lining of the
uterus are removed
5. _ _______ and _________ through the vagina
become bigger
du

Uterus
______

Both males and females

E

______ 1. Growth spurt

and around pubic area
2. Hair _________ under armpits
in pores and causes pimples
n

3. _________ skin that blocks sk

to
ls

ra? Tick (🗸).

How should the children help Ve
A

d as Vera is experiencing
Ada can give Vera a sanitary pa
pare a change of clothes for
menstruation. Ada can also pre
Vera too.
)

quickly as Vera is hurt.

(c

Tim should call the ambulance

e papers from her bag. Tell Vera
Cyrus can pass Vera some tissu
ketchup sauce on her chair.
aloud that she has spilled some kboo
k
or
Consolidation worksheet
W

Growing Up and Puberty 169

 Science keywords

Chapter 1 Page Chapter 6 Page

grams, kilograms, mass 3 reflected 83
gravity, newtons, weight 4 crescent Moon, Earth, new Moon, Sun 88
planets, Solar System, Sun 8 full Moon, gibbous Moon, half Moon, orbit, phase 89

d
orbit 10 medium 91
Moon, satellite 11 refraction 93

Lt
balanced, normal force 12
accelerate, applied force, friction, speed, unbalanced 14
Chapter 7 Page
decelerate 15
chemical reaction, combustion 97
buoyant force 16

te
products, reactants 98
displace, volume 17
colour change, indicator, odour change 100
float, sink 20

P
Chapter 8 Page
Chapter 2 Page
dissolve, solute, solution 111
body system, exhale, inhale, respiratory system 23
energy, particles 114

on
alveoli, bronchi, bronchioles, lungs, trachea 24
arteries, blood, blood vessels, capillaries, circulatory
28
system, heart, red blood cells, veins
Chapter 9 Page
circulation, double circulatory system, respiration 29
grains, rock, mineral 121
pulse 30

ti
igneous rock, magma 123
erosion, decay, sedimentary rock, sediment,
124
weathering
Chapter 3 Page
ca
fossil, sedimentation 125
infection, infectious disease, pathogen 37
geological time 127
fungi, host, spore, transmit, virus 38
metamorphic rock, metamorphism, pressure 128
bacteria 39
du

rock cycle 130

parasite 40
burial, melting, solidify 133
transmission 41
bedrock, soil 134
hygiene 43
clay, composition, consistency, sand, silt, texture 135
insect vector 44
E

clay soil, humus, loamy soil, organic material, sandy soil 138
barrier, defence mechanism, mucus, secretion, skin,
47
stomach acid

Chapter 10 Page
n

Chapter 4 Page ecosystem, food chain, food web, photosynthesis,

145
producer
physical change, reversible, substance 51
to

carnivore, herbivore, omnivore, predator, prey, primary

gas, liquid, mass, physical property, solid, temperature 146
54 consumer, secondary consumer, tertiary consumer
melting 56 energy flow 151
freezing, solidifying 57 energy source 153
ls

boiling, condensation 58 air pollution, deforestation,

154
global warming, overhunting
carbon dioxide, helium, hydrogen, nitrogen, oxygen 60
reforestation 155
energy, evaporation, steam
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62
toxic substance 156
bioaccumulation, ingest 157
Chapter 5 Page concentration 158
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energy, heat 69
thermal conductor 70
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Chapter 11 Page
thermal insulator 71
adolescent, hormone, puberty 161
thermal conductivity 72
breasts, menstruation, penis, pubic area, testes 163
buzzer, cell, circuit, circuit diagram, component, lamp, switch 74
egg, ovary, oviduct, reproductive system,
parallel circuit, series circuit 75 164
sperm, uterus, vagina
electrical conductivity 78 sperm duct 165
electrical conductor, electrical insulator 79 menstrual cycle 166

170 Science keywords

 Credits
Chapter 2 — p.31: Jarun Ontakrai/Shutterstock.com (Blood cells)

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Chapter 3 — p.38: Kateryna Kon/Shutterstock.com (Rhinovirus); nobeastsofierce/Shutterstock.com (Measles virus); Kateryna Kon/Shutterstock.com
(Fungus); p.39: Kateryna Kon/Shutterstock.com (Mycobacterium tuberculosis bacteria); Kateryna Kon/Shutterstock.com (Vibrio cholerae); p.40: Kateryna

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Kon/Shutterstock.com (Malaria); Kateryna Kon/Shutterstock.com (Toxoplasmosis parasite)

Chapter 4 — p.51: ReaLiia/Shutterstock.com (A hand holding crushed paper); Gus Andi/Shutterstock.com (Crushed tin can); ifong/Shutterstock.com
(Ice cube melting); Kei Shooting/Shutterstock.com (Boiling water); Gepardu/Shutterstock.com (Folded and unfolded paper); p.53: Mita Stock Images/
Shutterstock.com (Sandcastle); xpixel/Shutterstock.com (Broken green bottle); Ermak Oksana/Shutterstock.com (Blue torn paper strips); p.54: t.max/
Shutterstock.com (Haircut); Leestudio/Shutterstock.com (Cutting nails for a kid using nail clipper); p.61: Nikita_Stepanov/Shutterstock.com (Aluminium

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can); Realstockvector/Shutterstock.com (Silverwares); Superstar Production/Shutterstock.com (Red chair); JeniFoto/Shutterstock.com (Plastic beach
toys); Woodpond/Shutterstock.com (Pouring water from a plastic bottle into a glass beaker); Yellow Cat/Shutterstock.com (Hand with chocolate); Soft
Lighting/Shutterstock.com (Melted metal); p.65: Steven Coling/Shutterstock.com (Boiling water on gas flame)

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Chapter 5 — p.72: Meeza Design/Shutterstock.com (Red yarn); Retouch man/Shutterstock.com (Diamond); koosen/Shutterstock.com (Stainless steel
empty plate); ILYA AKINSHIN/Shutterstock.com (Spoon); AlenKadr/Shutterstock.com (Plastic bottle)

Chapter 7 — p.97: g215/Shutterstock.com (Burning paper); p.101: KrimKate/Shutterstock.com (Cooking sugar); Abramov Timur/Shutterstock.com (Apple

on
rotting); p.105: Toukung design/Shutterstock.com (Iron bars); aydngvn/Shutterstock.com (Rusted iron bars); p.106: Panupong786/Shutterstock.com (Iron
nail); MRS. NUCH SRIBUANOY/Shutterstock.com (Rusted iron nail); N-studio/Shutterstock.com (Burning wood)

Chapter 9 — p.121: michal812/Shutterstock.com (Granite rock); Aleksandr Pobedimskiy/Shutterstock.com (Sandstone rock); ZGPhotography/Shutterstock.
com (The beautiful Azure Window); Aleksandr Pobedimskiy/Shutterstock.com (Limestone with sea shells); p.123: Tyler Boyes/Shutterstock.com (Basalt);
Bjoern Wylezich/Shutterstock.com (Obsidian); Stas Malyarevsky/Shutterstock.com (White pumice); p.126: Yes058 Montree Nanta/Shutterstock.com

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(Shale); Susan Newcomb/Shutterstock.com (Sandstone); vvoe/Shutterstock.com (Siltstone); Aleksandr Pobedimskiy/Shutterstock.com (Limestone);
anne-tipodees/Shutterstock.com (Fossil in sandstone); p.127: Paulo Afonso/Shutterstock.com (Oldest fossil); p.128: vvoe/Shutterstock.com (Marble);
Tyler Boyes/Shutterstock.com (Gneiss); Yes058 Montree Nanta/Shutterstock.com (Slate); Nikitin Victor/Shutterstock.com (Metamorphic rock);
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p.130: www.sandatlas.org/Shutterstock.com (Igneous rock); KrimKate/Shutterstock.com (Polished siltstone); Yes058 Montree Nanta/Shutterstock.com
(Schist rock); Aleksandr Pobedimskiy/Shutterstock.com (White limestone); vvoe/Shutterstock.com (White marble); michal812/Shutterstock.com (Brown
sandstone); www.sandatlas.org/Shutterstock.com (Quartzite); p.138: photoste/Shutterstock.com (Worms in the ground); Sarah Saa/Shutterstock.com
(Plant decay); p.140: govindamadhava108/Shutterstock.com (Sandy soil); Niwet Kumphet/Shutterstock.com (Clay Soil)
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Chapter 10 — p.151: Vikki Olds/Shutterstock.com (Nutrition facts of chocolate); p.154: Gorlov-KV/Shutterstock.com (Wildfire); Peter Yeeles/Shutterstock.
com (Cane toad in tropical rainforest); Andrei Stepanov/Shutterstock.com (Whale hunt); p.155: Jordi C/Shutterstock.com (Orphaned elephants);
Jef Wodniack/Shutterstock.com (Takahe); WitR/Shutterstock.com (Safari in Kruger National Park); Breck P. Kent/Shutterstock.com (Cleaning up spilled
crude oil); TFoxFoto/Shutterstock.com (A large powered surface oil skimmer); Motortion Films/Shutterstock.com (Close-up of volunteers planting)
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Active Science

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The series is developed hold discussions that precede the teaching of every key
to comprehensively cover all the learning objectives of concept. Learners will need to collaborate with their
the Cambridge Primary Science curriculum framework peers, infer concepts and draw conclusions. Learners
(0097). The series adopts an Active Learning approach, will solve the case by the end of the chapter. This is

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which allows learners to actively build their own supplemented by colourful illustrations and easy-to-
understanding through exploration, discussion and read explanations to solidify their understanding. Well-
problem-solving. crafted exercises at various learning points help learners

on
to assess their learning and build process skills.
Learners will investigate science strands like Biology,
Chemistry, Physics and Earth and Space. Learners are Learners will also learn how to apply scientific knowledge
also taught to Think and Work Scientifically, which to the real world in Science in Context. With greater

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develops learners’ scientific enquiry skills and practical involvement in their learning, learners are challenged
skills. to think critically, reason logically and become effective
problem solvers. They will also develop a love for science
To encourage problem-based learning (PBL), each
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as they recognise its importance and relevance in their
chapter starts with a case problem. In each chapter, daily lives.
learners will explore anchor investigation activities and
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The series • Textbook • Downloadable resources for teachers,

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consists of: • Workbook including printables for hands-on

• Teacher’s Guide activities, worksheets and
• Digital Textbook, Workbook, test papers.
and Teacher’s Guide
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