LOWER SECONDARY SCIENCE TEXTBOOK

10.2 Properties of Gases

You should be able to:
• briefly describe the physical and chemical properties of the

gases found in air;
• describe tests to identify the following gases:

i) oxygen – rekindles a glowing splint,
ii) carbon dioxide – forms a white precipitate with limewater

(calcium hydroxide solution), and
iii) water vapour – turns blue cobalt chloride paper pink.
• list some uses of oxygen, carbon dioxide, nitrogen, helium,
neon and argon.

The gases in air have many properties.

Oxygen

Oxygen is the second most abundant gas in air and is
essential for life. Oxygen:
• has no smell (odourless),
• is colourless,
• supports life, and
• supports combustion (burning).

Super Scientist

Iron rusts when exposed to oxygen and moisture. In 1774, an English
chemist, Joseph
Priestly, first isolated
a gas which he called
‘super air’. When
he breathed in this
gas, he felt relaxed
and light-headed.
This ‘super air’ was
oxygen!

Gases 25

Identifying oxygen
When a glowing splint is inserted into a test tube containing
oxygen, it bursts into f lames (rekindles).

Glowing splint

WB Link Activity 10.1 Oxygen gas
Oxygen rekindles a glowing splint.

Science Bites Carbon dioxide

When fossil fuels are Carbon dioxide is the densest gas in air. It is used by plants
burnt, they produce for photosynthesis. Carbon dioxide:
carbon dioxide. Due • is odourless,
to the increased use • is colourless, and
of fossil fuels, the • does not support combustion.
percentage of carbon
dioxide in the air has Identifying carbon dioxide
increased. When carbon dioxide is passed through limewater (calcium
hydroxide), it forms a white precipitate called calcium
carbonate. A precipitate is a substance which is insoluble
in water.

Carbon dioxide

WB Link Activity 10.2 Clear limewater White precipitate
26 Gases
Before carbon dioxide After carbon dioxide
is bubbled through is bubbled through

Nitrogen

Nitrogen is the most abundant gas in the air. There is no
simple test for nitrogen as it is an unreactive gas. Nitrogen:
• is odourless,
• is colourless, and
• does not support combustion.

Noble gases

Noble gases are also known as inert gases. Helium, neon,
argon, krypton, xenon and radon are noble gases.

Period Group Æ
Ø
I II
III IV V VI VII 0

1 4

1H He

Hydrogen Helium

1 2

7 9 11 12 14 16 19 20

2 Li Be B C N O F Ne

Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

3 4 5 6 7 8 9 10

23 24 27 28 31 32 35.5 40

3 Na Mg Al Si P S Cl Ar

Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon

11 12 13 14 15 16 17 18

39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84

4K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

85 88 89 91 93 96 99 101 103 106 108 2 11 5 11 9 11 122 128 127 131

5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

133 137 139 178 181 184 185 190 192 195 197 201 204 207 209 At Rn

6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po Astatine Radon

Caesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium 85 86

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84

226 227

7 Fr Ra Ac

Francium Radium Actinium

87 88 89

The Periodic Table

These gases:
• are unreactive,
• are colourless, and
• do not support combustion.

Gases 27

Water vapour

The percentage of water vapour in the air varies with
temperature and pressure. Water vapour is:
• odourless, and
• colourless.
Identifying water vapour

Blue cobalt
chloride paper

WB Link Activity 10.3 Beaker
Boiling water

Testing for water vapour

Water or its vapour will turn blue cobalt chloride paper to pink.

Try this

Anhydrous copper sulfate is
a white powder. It turns blue
when water is added. It will
also turn blue slowly when
exposed to air, proving that
air contains water vapour.

28 Gases

Uses of gases in the air

Oxygen
This is the most important of all gases in the air. Oxygen
supports combustion. It is also used during respiration by
plants and animals.

When gases burn in pure oxygen, Scuba divers carry a tank that stores
they burn at very high temperatures. compressed air. It is used for breathing
Such temperatures are often high under water.
enough to melt most metals.

Carbon dioxide
There is only a small amount of carbon dioxide in the air but it
has many uses. Carbon dioxide is used in photosynthesis, f ire
extinguishers, the food industry and in the making of dry ice.

Carbon dioxide is used in Solid carbon dioxide is used to freeze and
some fire extinguishers. It preserve food like ice-cream. It is also known as
‘dry ice’.
does not support combustion.
Gases 29

Nitrogen
Nitrogen is generally unreactive. It is used as a
preservative in the food industry and to make fertilisers.

Fertilisers contain nitrogen These packets of crispy food contain nitrogen gas. This
compounds which are essential helps preserve the food.
for healthy plant growth.
Noble gases
The inert nature of these gases gives them many different
uses in daily life.

Argon gas in the bulb Helium is lighter than air and is used in airships and party
prevents the filament balloons.

from burning.

Quick Check Neon is used in advertising signs because it
is able to produce bright and colourful lights.
1. Describe a test to identify
oxygen gas.

2. Describe a test to identify
carbon dioxide gas.

3. Which gas in the air
supports combustion?

4. Which gas is
normally used in f ire
extinguishers?

5. Name three noble gases
found in air.

6. Which gas is used in
advertising signs?

30 Gases

10.3 Hydrogen

You should be able to:
• state the physical properties of hydrogen;
• describe a test to identify hydrogen;
• describe the preparation and collection of hydrogen by the

reaction of zinc with dilute acids;
• state the word equation for the preparation of hydrogen; and
• state the uses of hydrogen.

Properties of hydrogen

Hydrogen is the f irst element in the Periodic Table. It is the
lightest of all gases.

Period Group Æ
Ø
I II
III IV V VI VII 0

1 4

1H He

Hydrogen Helium

1 2

7 9 11 12 14 16 19 20

2 Li Be B C N O F Ne

Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

3 4 5 6 7 8 9 10

23 24 27 28 31 32 35.5 40

3 Na Mg Al Si P S Cl Ar

Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon

11 12 13 14 15 16 17 18

39 40 45 48 51 52 55 56 59 59 64 65 70 73 75 79 80 84

4K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

85 88 89 91 93 96 99 101 103 106 108 2 11 5 11 9 11 122 128 127 131

5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

133 137 139 178 181 184 185 190 192 195 197 201 204 207 209 At Rn

6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po Astatine Radon

Caesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium 85 86

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84

226 227

7 Fr Ra Ac

Francium Radium Actinium

87 88 89

Hydrogen in the Periodic Table

Hydrogen is: A lighted
• the lightest gas, pop splint
• odourless and colourless,
• insoluble in water,
• highly f lammable, and
• burns in air to produce water vapour.

Identifying hydrogen Acid
Metal
The presence of hydrogen can be tested by the following Testing for the presence
experiment. of hydrogen
Hydrogen gas is produced when a metal reacts with an acid.
If a lighted splint is held near the mouth of the test tube, the Gases 31
hydrogen burns with a ‘pop’ sound.

Preparation of hydrogen

Hydrogen is prepared by the following experiment. The zinc
reacts with hydrochloric acid and bubbles of hydrogen gas are
given off.

Thistle
funnel
Hydrochloric

acid

Side Delivery Hydrogen
arm tube gas
flask Test tube
Zinc Acid
granules Trough
containing
water

Preparation of hydrogen

The word equation for the reaction is:

zinc + hydrochloric acid zinc chloride + hydrogen
(metal) (acid) (a salt) (gas)

WB Link Activity 10.4 Other metals such as magnesium and iron, can also react with
acids to produce hydrogen.

Science Bites The Hindenburg disaster

The Hindenburg was
a giant hydrogen
airship built in
the 1930s by the
Germans. It was filled
with hydrogen, which
is lighter than air. In
1937, the Hindenburg
caught fire, killing
many people. Since
then, hydrogen has
never been used in
commercial airships
or balloons.

32 Gases

Uses of hydrogen

Hydrogen is produced on a large scale because it has a variety
of industrial and commercial uses.

Fuel Weather balloon

When hydrogen burns, it Hydrogen is the lightest gas
produces large amounts of and is therefore ideal for
energy. Hydrogen, as a fuel, weather balloons that go high
has the advantage of burning up in the atmosphere.
with no pollution products,
as its only by-product is
water.

Margarine Quick Check

Hydrogen is used in the 1. Name two
manufacture of margarine substances which
from vegetable oils. The oil react together to
becomes a solid when hydrogen form hydrogen gas
is bubbled through at a certain and a salt.
temperature in the presence of
a nickel catalyst. 2. How do you test for
hydrogen?

3. Give three uses of
hydrogen.

4. Name the
substance
produced when
hydrogen is burned
in air.

Gases 33

Summary

Gases

Oxygen Carbon Nitrogen
• makes up 20% dioxide • makes up 79%
• makes up 0.03%
of air of air of air
• colourless and • colourless and • colourless and
odourless
odourless • does not support odourless
• supports life combustion • does not
• required by plants
and combustion for photosynthesis support
• causes metals • used in f ire combustion
extinguishers • used to f ill
to corrode • solid form is used packets of food
• stored in tanks to preserve food to prevent
the food from
for use in turning bad
hospitals and • used to make
industries fertilisers

to test for to test for
oxygen carbon dioxide
a glowing splint a white precipitate
bursts into f lames is formed when
carbon dioxide is
34 Gases bubbled through
limewater

Noble Water Hydrogen
gases vapour
• its percentage • the lightest of all
• make up about 1% in air changes gases
of air • colourless
and odourless • odourless and
• helium, neon, colourless
argon, krypton, to test for
xenon and radon water vapour • insoluble in water
cobalt chloride • highly f lammable
• unreactive paper changes • burns to produce
• colourless from blue to pink
• do not support water vapour
• produced during
combustion
• Helium is light the reaction
between metals
and unreactive, and acids
hence it is used in • used as a fuel
airships and party • used to produce
balloons margarine
• Neon is used • used to f ill
in advertising weather balloons
signs because it
produces bright, to test for
coloured lights hydrogen
• Argon prevents
f ilaments in light ignites with a
bulbs from burning ‘pop’ sound in
the presence of a
lighted splint

Gases 35

Review Questions

1 Which gas has the highest percentage composition in air?
A Argon
B Oxygen
C Nitrogen
D Carbon dioxide

2 Which of these gases is not present in air?
A Oxygen
B Nitrogen
C Hydrogen
D Carbon dioxide

3 Which of these gases is f lammable?
A Neon
B Oxygen
C Hydrogen
D Carbon dioxide

4 Which of these gases produces a white precipitate when bubbled
through limewater?

A Oxygen
B Nitrogen
C Hydrogen
D Carbon dioxide

5 Which of these is the lightest gas in air?
A Helium
B Oxygen
C Nitrogen
D Hydrogen

6 Which of these pairs contain only noble gases?
A Helium and argon
B Argon and oxygen
C Helium and nitrogen
D Oxygen and nitrogen

36 Gases

7 Which of these can be used to test for the presence of water vapour?
A Blue litmus paper
B Concentrated sulfuric acid
C Blue cobalt chloride paper
D Blue copper sulphate crystals

8 Which of these is a use of hydrogen gas?
A Making frozen food
B To help patients breathe
C Production of f izzy drinks
D Manufacture of margarine

9 Carbon dioxide, oxygen and hydrogen gases are colourless and
odourless. Give one test for each gas that would help to identify them.

10 a) The diagram below shows the apparatus set-up that is used to
prepare hydrogen in the laboratory. Identify the apparatus shown.

b) Write a word equation for the chemical reaction that takes place.

Gases 37

Chapter Transport System
in Humans
11
The heart is a vital organ in humans. It is part of the transport
system and pumps blood to all parts of the body. What is the role
of blood in the body? What are blood vessels and why are they
important to us? You will be learning more about the transport
system in this chapter.

Firman Allah Subhanahu Wa Ta`ala
Tafsirnya:
Bacalah (wahai Muhammad) dengan
nama Tuhanmu Yang menciptakan
(sekalian makhluk). (1) Dia telah
menciptakan manusia daripada
segumpal darah. (2)

Read! In the Name of your Lord Who
has created (all that exists). (1) He has
created Man from a clot (a thick mass of
coagulated blood). (2)

(Surah Al-`Alaq: Ayat 1-2)

Let’s Explore

• What are the different parts of the
heart and their functions?

• How is blood transported to all parts
of the body?

• What are the components of blood?
• What are the roles of the heart and

blood vessels in the transport system?

338 Transport System in Humans

11.1 Structure of the
Heart

You should be able to:
• identify:

i) the parts of the heart – the four chambers: ventricles,
atria

ii) the types of blood vessels – pulmonary artery, pulmonary
vein, aorta, vena cava

iii) valves;
• state the function of the heart;
• briefly describe the transport (circulatory) system in

humans with reference to the heart and blood vessels.

The transport (circulatory) system

In humans, the transport system carries nutrients and
oxygen to the cells. It removes waste products like carbon
dioxide and excess water from the cells in the body. This
system is also known as the circulatory system.
The transport system consists of:
i) The heart – an organ that pumps blood throughout

the body
ii) Blood vessels – tubes that carry blood within the body
iii) Blood – a fluid that transports substances throughout

the body.

Heart

The position of the heart

39Transport System in Humans

The heart
The heart is a muscular organ and is about the size of a
clenched fist. It lies between the lungs. The heart acts as a
‘pump’ that transports blood to all parts of the body.

Pulmonary Aorta
artery
Pulmonary vein
Right atrium Left atrium
Valves

Vena cava

Right ventricle Left ventricle
Thin wall of the Thick wall of the
left ventricle
right ventricle

Blood containing Structure of the heart
more oxygen
Blood containing
more carbon dioxide

Try this The heart has four chambers. They are:
• two upper chambers called the right atrium and the left
The size of the heart
is closely related to atrium, and
body size. Generally, • two lower chambers called the right ventricle and the
the heart weighs
0.59% of the total left ventricle.
body mass. Calculate On the left side of the heart, the chambers have blood rich
the mass of your in oxygen (oxygenated blood) and on the right side, the
heart using this chambers have blood with less oxygen and more carbon
formula. dioxide (deoxygenated blood).
The left ventricle has a thicker wall than the right ventricle.
WB Link Activity 11.1 This is because it needs to exert a larger force in order to push
blood to all parts of the body.
The valves in the chambers prevent the blood from flowing
backwards. This ensures that the blood flows in one direction.

40 Transport System in Humans

Blood circulation

Blood flowing through the transport system is known as blood
circulation. The heart pumps the blood to the lungs and back
to the heart. The blood from the heart is then pumped to the
rest of the body and returns to the heart. The heart keeps
the blood circulating. The following diagram shows the path of
blood in the transport system.

2 3
The right ventricle pumps Blood entering
blood to the lungs. The blood the left atrium
releases carbon dioxide and from the lungs is
collects oxygen. rich in oxygen.

To the lungs From the lungs

1 Right atrium Left atrium
Blood entering the
right atrium from the 4
rest of the body has The left ventricle
very little oxygen. pumps blood to the
Instead, it is rich in rest of the body.
carbon dioxide.

Right ventricle
Left ventricle

From the rest To the rest of Science Bites
of the body the body
As the blood
Blood containing more oxygen circulates around the
Blood containing more carbon dioxide body, blood passes
through the heart
Circulation of blood in the transport system twice. This is called
double circulation.

Quick Check

1. What does the transport system consist of?
2. State the function(s) of the heart, blood and valves.

41Transport System in Humans

11.2 Blood

You should be able to:
• state that the main function of blood is to transport food

(nutrients) and oxygen to all parts of the body and to
remove waste products and carbon dioxide from the body;
• identify the components of blood – red blood cells, white
blood cells, plasma and platelets;
• identify the three main types of blood vessels as arteries,
veins and capillaries;
• describe the functions of arteries, veins and capillaries;
• show an awareness of the heartbeat, pulse and blood
pressure.

The body contains about 4-5 litres of blood that flows constantly
in our transport system.

Function of blood

Blood transports food (nutrients) and oxygen to all parts of
the body and removes waste products such as carbon dioxide.

Capillary wall

Key: Cell
Oxygen and nutrients pass from the blood into
the cells
Waste products pass from the cells into the blood

Transfer of oxygen from the blood into the tissues

As blood flows to different parts of the body, nutrients and
oxygen pass from the blood into the cells. Waste products
such as carbon dioxide pass from the cells into the blood.

42 Transport System in Humans

Blood and its components

Blood can be separated into its components – red blood cells,
white blood cells, plasma and platelets.

Plasma
(about 55% of total blood)

White blood cells and platelets
(less than 1% of total blood)
Red blood cells
(about 45% of total blood)
The components of blood

The following is a microscopic image of a blood sample.

Platelets

Plasma
White blood cell

Red blood cell

The components of blood Science Bites

Red blood cells When a person loses
Red blood cells are biconcave (concave on both sides) and too much blood, a
have no nucleus. blood transfusion is
carried out. There are
A group of red blood cells four main types of
blood – A, B, AB and
The biconcave shape increases the surface area of the red O. These are known
blood cell. This allows the cells to take in and release oxygen as blood groups.
at a faster rate. The blood being
transfused must be
matched with the
blood type of the
person.

43Transport System in Humans

White blood cells
White blood cells are larger than red blood cells. However, they
are fewer in number. The white blood cells protect the body
against infections and diseases.

Bacteria

White blood Bacteria engulfed
cell engulfing or taken into the
bacteria cytoplasm

A white blood cell destroying bacteria

Plasma
Plasma is a light yellow liquid, containing mainly water. Many
substances such as nutrients are dissolved in it. Red blood
cells, white blood cells and platelets are suspended in plasma.
Platelets
Less than 1% of blood is made up of platelets. When there is
a cut in the skin, platelets group together at the cut and this
causes blood to clot. This prevents further bleeding and allows
the skin to start healing.

WB Link Activity 11.2

44 Transport System in Humans

Blood vessels

Blood is transported by blood vessels. There are three types of
blood vessels – arteries, veins and capillaries.

Artery
Valve

Vein

Capillaries
Types of blood vessels

Arteries carry blood away from the heart under high pressure. Science Bites
Therefore, arteries have thick walls to withstand the pressure
of blood flowing through them. Using a stethoscope,
Veins carry blood back to the heart at low pressure. Therefore, we can hear our
they have thinner walls compared to the arteries. Valves are heart making
present in veins to ensure that blood flows in one direction. rhythmic ‘lub-dub’
Capillaries are tiny blood vessels that are found between the sounds. These
cells of almost all the tissues of the body. They are only one sounds are produced
cell thick. This allows a quick exchange of substances between when the valves open
the blood and the tissues. and close.

Pulse and blood pressure

Our heart keeps on pumping blood throughout our entire
lifetime at about 72 beats per minute (bpm). Each time the
heart beats, a pulse is produced. The number of pulses per
minute is known as the pulse rate. It is equivalent to the
heart rate.

Taking the pulse rate

45Transport System in Humans

During exercise, cells require more energy. As such, the
heart beats faster to allow nutrients and oxygen to reach
the cells faster.

WB Link Activity 11.3 The heart beats faster during
vigorous activities.

Blood pressure is the force that blood exerts on the walls
of arteries as the left ventricle pumps the blood to the rest of
the body. It can be measured using an instrument called the
sphygmomanometer. When we engage in physical activities
such as running, climbing a flight of stairs and hiking, our
heart beats faster. This results in increased blood pressure.

The sphygmomanometer

Quick Check

1. What are the functions of blood?
2. Name the four components of blood.
3. State the differences between an artery, a vein and a

capillary in terms of:
a) thickness.
b) function.
4. Define pulse rate and blood pressure.

46 Transport System in Humans

Summary

Transport System
in Humans

consists of

Heart Blood Blood
consists of vessels
is divided
into four • Red blood cells consist of
chambers • White blood cells • Arteries
• Plasma • Veins
• Left atrium • Platelets • Capillaries
• Right atrium
• Left ventricle
• Right ventricle

47Transport System in Humans

Review Questions

1 The human transport system is made up of three main components.
Which of the following are the three main components?
A Heart, blood and arteries
B Heart, blood vessels and blood
C Red blood cells, heart and blood vessels
D Red blood cells, white blood cells and platelets

2 Which of the numbered blood vessels carry oxygenated blood?

3
24
1

A 1 only
B 3 only
C 2 and 3 only
D 3 and 4 only
3 Which part of the heart exerts the highest pressure?
A Left atrium
B Left ventricle
C Pulmonary vein
D Pulmonary artery
4 Which one of the following statements about the heart is not true?
A It has blood vessels.
B It is an organ in our body.
C It is part of the digestive system.
D It contracts and relaxes continuously.

48 Transport System in Humans

5 What is the function of a white blood cell?
A It helps repair wounds.
B It helps in the clotting of blood.
C It protects the body against diseases.
D It carries oxygen to all parts of our body.

6 The diagram below represents our transport system. Which pair of
blood vessels carries blood that is rich in oxygen?

Lungs
AB

Heart

CD
Parts of the body

A A and B
B A and C
C B and D
D C and D
7 The following sentences describe how blood flows in the body.
Rearrange the sentences in the correct order to show how the
transport system works.
• The heart pumps blood to the lungs.
• The heart pumps blood to the rest of the body.
• The blood is now rich in oxygen and is transported back to the heart.
• In the lungs, the blood exchanges carbon dioxide for oxygen.
• The blood has more carbon dioxide and flows back to the heart again.
• As the blood is transported around the body, oxygen is used up

and carbon dioxide enters the blood.

8 State the role of blood plasma in our transport system.

9 State one difference between the blood carried in an artery and the
blood carried in a vein.

49Transport System in Humans

10 Observe the diagram below. State the differences between the blood
vessels found in the diagram.

Artery

Valve

Vein

Capillaries

11 Huda exercised for a few minutes before resting. The graph below
shows her pulse rate over a period of one hour.

150 Q

Pulse rate (beats per minute) 100 RS

P
50

10 20 30 40 50 60
Time (minutes)

a) Which part of the graph shows that she is exercising?
b) Which point(s) on the graph shows her normal pulse rate?
c) Why does her pulse rate increase when she is exercising?

50 Transport System in Humans

Chapter Plant and Animal

12 Nutrition

The pitcher plant is a plant that is usually found growing in
nutrient-poor soil. In order to supplement its nutrients, it needs
to feed on insects. To digest its food, the insect is trapped and
bathed in the plant’s digestive juices till it softens. This is how
the pitcher plant digests food to get the nutrients it needs. Do
you think we digest our food in the same way as these plants
do? Let us find out from this chapter.

Firman Allah Subhanahu Wa Ta`ala:
Tafsirnya:
Wahai anak Adam! Pakailah pakaian
kamu yang indah pada tiap-tiap kali
kamu ke masjid (atau mengerjakan
solat) dan makanlah serta minumlah
dan jangan pula kamu melampaui batas.
Sesungguhnya Allah tidak menyukai
orang yang melampaui batas.(31)

O Children of Adam! Take your adornment
(by wearing your clean clothes), while
praying [and going round (the Tawaf of)
the Ka`bah,] and eat and drink but waste
not by extravagance, certainly He (Allah)
likes not Al-Musrifiin (those who waste
by extravagance).(31)

(Surah Al-A`araf: 31)

Let’s Explore

• What is photosynthesis?
• What is the primary source of

food?
• Why do we need food?
• What is the importance of a

balanced diet?
• What is digestion?
• What is the role of enzymes in

digestion?

51Plant and Animal Nutrition

12.1 Photosynthesis

You should be able to:
• define photosynthesis as the process by which plants

manufacture food using carbon dioxide and water in the
presence of sunlight and chlorophyll;
• state the word equation for photosynthesis.

Photosynthesis is the process by which green plants, in the
presence of light energy and chlorophyll, make glucose (food)
from carbon dioxide and water. This process releases oxygen
as a by-product.

The process of photosynthesis can be summarised in this
word equation:

Carbon dioxide + Water Light energy Glucose + Oxygen
Chlorophyll

Source of Oxygen
energy

Carbon
dioxide is
absorbed
from the air

Oxygen
is given out
by the leaves

Water from soil

Photosynthesis in plants

Glucose, which is a simple sugar produced during
photosynthesis, provides energy for the plants.

Super Scientist

Joseph Priestley (1733–1804), a chemist,
discovered photosynthesis and interpreted
his first experiments on it. In 1772, he
observed that a mouse died when it
was left alone in a jar of air and another
survived when it was enclosed with a
plant. After further experiments, Priestley
had proved that plants could change the
composition of air.

52 Plant and Animal Nutrition

Raw materials and conditions necessary
for photosynthesis

In order for plants to photosynthesise, they must have the raw
materials as well as the appropriate conditions. Carbon dioxide
and water are the raw materials. The conditions required for
photosynthesis are the presence of sunlight and chlorophyll.

Light energy from the Sun
Light energy is converted to
chemical energy stored in
glucose.

Chlorophyll Carbon dioxide is Water from
This green pigment absorbs absorbed from the air. the roots
light energy and converts
it into chemical energy
needed to manufacture
glucose.

Raw materials and conditions necessary for photosynthesis in plants

Quick Check WB Link Activity 12.1

1. Def ine photosynthesis.
2. State the word equation for photosynthesis.

53Plant and Animal Nutrition

12.2 Food and its
Importance

You should be able to:
• state that plants are the primary source of food;
• state that food is a source of energy for living things;
• describe the dietary importance of protein, carbohydrates,

fats, f ibre, vitamins, mineral salts, and water;
• describe one test each for:

i) proteins using the Biuret test,
ii) glucose using Benedict’s solution,
iii) starch using iodine solution, and
iv) fats and oil using the grease spot test.
Plants are living organisms that produce their own food. This
makes them an important source of food for most living things.
We need food to:
• repair worn out tissues,
• maintain a healthy body,
• grow new cells and tissues, and
• provide us with energy for our daily activities like walking.

Humans and animals depend on food to supply them with energy for their
daily activities.

54 Plant and Animal Nutrition

Nutrients Science Bites

The food we eat may be grouped as follows: Proteins,
• proteins, carbohydrates, fats,
• carbohydrates, f ibre and vitamins
• fats, are known as organic
• f ibre, food substances
• vitamins, because they contain
• mineral salts, and the element, carbon.
• water. Water and mineral
All of these foods, except water and f ibre, are called nutrients. salts are known
Proteins, carbohydrates and fats are the three main types as inorganic food
of food that supply the body with energy. Different food substances.
substances have different roles in the body. Let us take a look
at the different types of food and their importance. Science Smart

Proteins According to the Joint
Proteins are one of the basic building blocks of the human Food and Agriculture
body, making up about 16% of our total body mass. Let us Organization (FAO),
look at their importance and the sources. World Health
Organization (WHO)
Sources of proteins and United Nations
University (UNU)
Expert Consultation
on Protein & Amino
Acid Requirements
in Human Nutrition,
2002, a median
requirement of 660 g
per day of protein
can be estimated as
the best estimate of
a population average
requirement for
healthy adults. (Note:
The safe level of
protein intake would
be 830 g per day.)

Importance of proteins Sources of proteins
They are needed to: Proteins can be found in
• provide us with energy, food such as meat, f ish,
• build new cells for body growth, and milk, eggs, nuts and
• repair of worn-out tissues. cheese.

Importance and sources of proteins

Def iciency of proteins may lead to a disease known as
kwashiorkor, which causes swollen abdomens.

Kwashiorkor in a
young child

55Plant and Animal Nutrition

Test for proteins
The Biuret test is used to detect the presence of proteins.
A few drops of Biuret solution are added to the food sample
containing proteins, shaking after each drop. Proteins are
present if the colour of the sample changes to purple.

Biuret’s
solution

Food sample Purple
in solution colour

WB Link Activity 12.2 Shake
Biuret’s test
Science Bites
Carbohydrates
Carbohydrates are Carbohydrates are the principle source of energy in most
a good source of humans. It provides between 40–80 % of total energy intake
energy. However, in different populations*. Sugars and starch are examples of
when consumed in carbohydrates. There are many kinds of sugars such as glucose
excessive amounts, and sucrose. Starch is present in plant food such as potatoes,
it can be converted tapioca and rice. The following table shows the importance
to fats. and sources of carbohydrates.

Sources of carbohydrates

Importance of Sources of carbohydrates
carbohydrates

Carbohydrates are Carbohydrates are found mainly in food
an immediate source like rice, bread, noodles and potatoes.
of energy.

Importance and sources of carbohydrates

*Based on the food pyramid structure (Gangsa Pemakanan Sihat) and National
Dietary Guidelines.

56 Plant and Animal Nutrition

Test for starch
Iodine is used to test for the presence of starch. A few drops
of iodine solution are added to the food sample containing
starch. Starch is present when the colour of iodine turns
from brown to blue-black. It is absent when the colour
remains unchanged.

Drops of iodine Turns blue-black
solution
Piece of
bread

Iodine test

Test for glucose
Benedict’s solution is used to test for the presence of
glucose in food samples. The food samples must be in solution
form. An equal volume of Benedict’s solution is added to
the solution. The mixture is then warmed in a beaker of hot
water. Glucose is present if the colour of the sample changes
to an orange or red precipitate. It is absent when the colour
remains unchanged.

Benedict’s
solution

Food Orange
containing precipitate
glucose
Activity 12.3 &
Benedict’s test
WB Link Activity 12.4

Fats
Fats provide almost twice as much energy as proteins and
carbohydrates. They are important for good health. The
following table shows the importance and sources of fats.

Importance of fats Sources of fats
Fats provide us with: Fats can be found in food such as
• energy, and oil, butter and nuts.
• warmth.

Importance and sources of fats

57Plant and Animal Nutrition

Test for fats
The grease spot test is used to detect the presence of fats.
When a drop of food sample is placed or smeared on a piece
of f ilter paper and allowed to dry, a translucent spot is formed.
This spot is known as the grease spot and it indicates the
presence of fat.

Food sample
Filter paper

WB Link Activity 12.5 Grease spot test

Fibre
Fibre is obtained from plant materials. Fibre cannot be
digested and will be passed out of the body. Fibre absorbs
water, making the waste matter soft, preventing constipation.
Constipation is the result of eating too little f ibre and causes
faeces to become dry and hard, making it diff icult to expel
from the body. The following table shows the importance and
sources of f ibre.

Sources of fibre

Importance of fibre Sources of fibre

Fibre keeps our digestive system A variety of beans, fruits,
healthy by: vegetables and whole grain
• providing bulk to faeces, and products such as wholemeal
• helping to prevent constipation. breads, oats and cereals

Importance and sources of fibre

58 Plant and Animal Nutrition

Vitamins Science Bites
Vitamins are naturally occurring chemicals in minute quantities
and can be found in most of the foods we consume. It has a Ultraviolet rays from
variety of functions in our body. Nonetheless, we only require the Sun help the skin
a small amount to keep us healthy. The table below shows the to produce Vitamin D.
importance of vitamins in our diet.

Sources of vitamins

Vitamin Main sources Functions Deficiency

A • Some yellow or It is needed for Deficiency of vitamin A
orange fruits such as healthy skin and causes night blindness
mangoes and papayas eyes. (poor night vision).
• Some vegetables such
as spinach, broccoli,
tomatoes and carrots

B • Fish, potatoes, and It is needed Deficiency of vitamin B
vegetables such as for a healthy causes beri-beri, a
broccoli and spinach nervous system. disease that leads to
the loss of function to
the muscles.

C • Citrus fruits such as It is needed for Deficiency of vitamin C
oranges, lemons, healthy blood, leads to a disease
kiwis and limes skin and gums. called scurvy, which
is characterised by
It increases the swollen bleeding gums,
body’s natural muscle weakness and
defences against joint pains.
diseases.

D • Eggs, cheese and It is needed for Deficiency of vitamin D
some fish such as strong bones causes weak and brittle
and teeth. bones leading to a
tuna

bone disease known as
rickets.

Importance of vitamins in our food intake

59Plant and Animal Nutrition

Mineral salts
Mineral salts, such as calcium and iron, are only required in
small amounts to keep us healthy and prevent diseases. Dark
green leafy vegetables and egg yolk contain a lot of iron.
Cheese, milk and peas are rich in calcium. The table below
shows the importance of mineral salts in our diet.

Sources of mineral salts

Minerals salts Main sources Functions Deficiency

• Dairy products It is essential to keep A deficiency in
such as milk, bones and teeth calcium leads
Calcium cheese and yoghurt strong and healthy. to rickets and
• Dark green leafy osteoporosis (brittle
vegetables bones).

• Liver, meat, It is essential for the A deficiency in
soybeans and formation of healthy iron can lead to a
Iron dark green leafy red blood cells. blood disease called
vegetables such as anaemia.
spinach

Iodine • Seafood such as It is essential for A deficiency of
crabs and seaweed normal growth. iodine leads to goitre
It is important for (swelling of the
the formation of thyroid gland in the
hormones of the neck).
thyroid glands.

Fluoride • Fish, tea and most It is essential for the A deficiency of
types of vegetables formation of healthy fluoride leads to an
bones and teeth. increased risk of
dental cavities.

The importance of mineral salts in our food intake

60 Plant and Animal Nutrition

Water Science Smart
Water is essential to life. Humans can live for several weeks
without food, but only for a few days without water. Water is You must drink at
important as water carries substances around the body and least six to eight
helps to remove wastes. Every day, you lose water through glasses of water
your breath, sweat, urine and faeces. For your body to function every day to make
properly, you must make sure that you consume enough water. sure that you
The table below shows the importance and sources of water consume enough
in our diet. water.

Fruits such as watermelon
contain a lot of water.

Importance of water Sources of water
Water: Beverages and foods that
• prevents constipation, contain water such as
• maintains normal body watermelons, cucumbers
temperature, and and radishes.
• prevents dehydration.

Importance and sources of water

61Plant and Animal Nutrition

Composition of foods

You can easily check the types of nutrients you are taking in
by looking at the food labels on a food package. By reading the
food labels, you can find out information about:
• all the ingredients that make up a food product, and
• the amount of energy, protein, fat, dietary fibre and nutrients

provided by the food products.

Quick Check The Nutrition Information Panel (NIP) is a table that
lists the quantities of key components of food and is
1. Why do we need required on most packaged food.
food?
INGREDIENTS: PREPARED
2. State the importance NAVY BEANS, WATER, SALT,
of proteins, SUGAR, DEHYDRATED
carbohydrates, fats, ONION, CALCIUM CHLORIDE
fibre, vitamins,
mineral salts and The ingredient list provides information about all
water. the ingredients that make up the food product in
this package.
3. How would you test
the presence of the
following in food:
i. protein?
ii. glucose?
iii. starch?
iv. fats?

62 Plant and Animal Nutrition

12.3 Balanced Diet

You should be able to:
• explain the importance of a balanced diet;
• state the effects of an unbalanced diet with reference to

obesity, diabetes, being underweight and coronary-related
conditions.

A balanced diet contains the correct proportion of proteins,
carbohydrates, fats, vitamins, mineral salts, f ibre and water.
Eating a balanced diet is important for all individuals. Each
individual has different nutritional needs. A balanced diet for
one person may not be balanced for another. Following the
HEALTHY PLATE’ portion or the food pyramid are two
main ways to ensure that your meal is a balanced diet.

‘HEALTHY PLATE’ portion

A ‘HEALTHY PLATE’ portion comprises of the following:

One serving of fruit A glass A glass
of water of milk

Half a plate of vegetables

Quarter plate of e
of proteins
carbohydrates Quarter plat
The ‘HEALTHY PLATE’ portion

63Plant and Animal Nutrition

Food Pyramid

The diagram below is the food pyramid. It divides foods
into groups, showing the correct proportion of the food
groups to eat.

EAT THE LEAST

EAT MODERATELY

EAT THE MOST

EAT ACCORDINGLY

Reduce the intake of
Fatty, oily, salty and sugary foods

Take a moderate intake of
Proteins:

2-3 servings a day
(1 serving = 2 pieces of ikan rumahan; or 1 piece of chicken thigh;

or 1 piece of tofu)
Dairy products:
2-3 servings a day
(1 serving = 1 glass of milk; or 1 slice of cheese)
Increase the intake of

Fruits:
2-3 servings a day
(1 serving: 1 apple or orange; or 6 rambutans; or 1 slice of watermelon
or papaya or pineapple)

Vegetables:
2-3 servings a day
(1 serving: 1 scoop of vegetables or 3 spoonfuls of vegetables)
Eat accordingly of
Complex carbohydrates:
8-12 servings a day
(1 serving: 1 scoop of rice or noodles; or 1 slice of bread; or 1 potato;
or 3 pieces of dry crackers)

64 Plant and Animal Nutrition

Eating junk food such as fast foods or foods high in salt, oil or
sugar may have harmful effects on health.

Junk food

An unbalanced diet

A diet consisting of too much or too little of a particular type
of food is an unbalanced diet. It does not supply the right
amounts of nutrients needed and often leads to malnutrition.
The effects of an unbalanced diet include:
• obesity,
• diabetes,
• underweight, and
• developing coronary heart diseases.
Obesity
When a person regularly eats too much of carbohydrates and
fats and does not exercise enough, he or she will become
overweight. If this continues, it may lead to obesity (extremely
overweight). Obesity causes major health problems, such as
heart diseases, stroke and diabetes. It also puts a strain on
the joints in the body.

Being overweight could An unhealthy lifestyle can also cause obesity.
lead to diseases.

Quick Check

1. State the importance of a balanced diet.
2. What are the effects of an unbalanced diet?

65Plant and Animal Nutrition

Diabetes
Diabetes is a disease caused by high levels of sugar in the
blood. This may lead to many other conditions such as kidney
damage and blindness. Diabetes can affect people of any age.
There is no cure for it. An unbalanced diet or a diet with high
sugar content can increase the risk of developing diabetes.
Underweight
When the amount of food that a person takes in is much less
than what is required daily, he or she may weigh less than
the expected weight of a healthy person. He or she is said to
be underweight. When a person is underweight, he or she
might not have enough nutrients for daily activities. Severely
underweight individuals may have poor physical stamina and a
weak immune system, leaving them open to infection.
Coronary heart diseases
A diet that contains a large amount of fats may lead to
coronary heart disease. The unhealthy diet that contains
large amounts of fats, or processed foods, may cause weight
gain. This can cause stress on the heart, as it needs to pump
blood harder to the larger body.

Teenagers need more energy than the elderly.

66 Plant and Animal Nutrition

12.4 Food Additives and Science Bites
Processed Food
‘Diet’ drinks contain
You should be able to: food additives that
• explain the harmful effects of food additives with reference to: are sweeteners,
for example the
i) children becoming too active, and chemical aspartame.
ii) cancer. This chemical is 200
Processed foods are defined as foods that are prepared and times sweeter than
packaged commercially for general consumption. Examples of an equal amount
processed foods are pickled foods, canned tuna and canned of sugar. It is less
drinks. During food processing, substances are added to the fattening because it
food to improve its texture, enhance its flavour, maintain contains less calories.
freshness and to protect the nutritional value of food. These However, it has been
substances are called food additives. claimed that it causes
headaches, mood
Pickled foods and canned foods contain food additives. swings and epilepsy.
There are even fears
There are three important types of food additives, that aspartame
preservatives, flavourings and colourings. increases the risk of
certain cancers.
Preservatives

Preservatives are added to food to keep food fresh for a
longer time and protect it against deterioration caused by
microorganisms. Some examples of preservatives are salts in
pickled foods, and nitrates in sausages.

Nitrates are used in the
preservation of sausages to keep
them fresh for a longer time.

67Plant and Animal Nutrition

Flavourings

Flavourings are added to enhance the f lavour of the food. An
example of f lavouring is monosodium glutamate (MSG).

Some instant noodles contain MSG, as a
flavouring.

Colourings

Food colouring is a substance that is added to foods or drinks
to improve their colour. An example of a food colouring is
tartrazine, which gives food its bright yellow colour. Food
colourings are used both in commercial food production and in
domestic cooking.

Local kuihs contain different colourings Candies contain colourings to enhance
to enhance their appearance. their appearance and taste.

Effects of food additives

Over recent years, there have been growing concerns
about the possible side effects of food additives. Frequent
and regular intake of food additives may cause harmful effects
such as:
• hyperactivity in children, and
• cancer.

68 Plant and Animal Nutrition

Hyperactivity in children
Some foods which contain additives such as colourings may
cause young children to become hyperactive. This results in
the child being restless and agitated.
Cancer
Most food additives used in food processing are artificial
substances. Some food additives, such as sodium benzoate
in soft drinks and tartrazine in candies, have been linked
to cancer.
It is important to check the food labels of the food that you
buy. The ingredients on the label will tell you if additives are
present in the food. It is advisable to consume food that
contains less or no additives to ensure a healthy diet.

Sparkling flavoured drink Ingredients for mushroom
Ingredients: Carbonated chicken flavoured instant noodles
water, sugar, citric acid,
flavourings, preservative Ingredients for noodle cake:
(sodium benzoate) and Wheat flour, palm oil, salt and food
quinine. Contains permitted conditioners (sodium carbonate,
food additives of non-animal sodium polyphosphate and
origins. potassium carbonate)

Ingredients for soup:
Salt, dextrose, hydrolysed vegetable
protein, mixed spices, mushroom
extract, and extract of seafood
and permitted flavour enhancers
(Monosodium glutamate, yeast
extract, disodium inosinate and
disodium guanylate), colour
(caramel).

Food labels indicate the presence of additives as its ingredients.

Quick Check

1. Give three reasons why food additives are used.
2. Give two possible harmful side effects of food additives.

69Plant and Animal Nutrition

12.5 Digestion in
Mammals

You should be able to:
• describe the role of teeth in mastication;
• explain why food must be digested;
• identify the main structures of the alimentary canal (mouth,

salivary glands, oesophagus, stomach, small intestine, large
intestine, liver, gall bladder, pancreas, rectum and anus);
• state the main function(s) of the mouth, stomach, small
intestine and large intestine;
• describe the role of digestive enzymes present in the
mouth, stomach and small intestine (limit to the three
classes of enzymes i.e. carbohydrase, protease and lipase);
• investigate how starch can be digested by saliva into a form
of simple sugar.

Why must food be digested?

The cells of our body need food for growth and energy. Food
contains carbohydrates, proteins and fats. These substances
are made of large and complex particles. As only small and
simple particles can pass through the cell membranes into the
cell, the food we eat must be broken down. In this section, you
will learn more about digestion and the digestive system.

Enzymes
Our body produces enzymes. They speed up the process
of digestion. The enzymes involved in the digestion of food
are carbohydrase, protease and lipase. Each enzyme acts on
specific food as shown in the table below.

Carbohydrase Protease

Starch Simple sugars Proteins Amino acids

Lipase

Fats Fatty acids
and glycerol

Enzyme Food End products
Carbohydrase Carbohydrates Simple sugars
Protease Proteins Amino acids
Lipase Fats Fatty acids and glycerol

The action of enzymes on food

70 Plant and Animal Nutrition

The digestive system Science Smart

Digestion occurs in the digestive system. All mammals have A gland is an organ
similar digestive systems. The digestive system has two parts: that secretes a
i. the alimentary canal – consists of the mouth, chemical substance.
For example, salivary
oesophagus, stomach, small intestine and large intestine glands secrete saliva.
(includes the rectum and anus);
ii. the associated organs consist of the liver and pancreas.
Let us take a look at the parts and their functions.

Salivary glands Mouth
Oesophagus
(or gullet)

Liver Stomach The
Gall bladder alimentary
Bile duct canal

Pancreas

Small intestine
Large intestine

Rectum
Anus

Parts of the digestive system

Food travels through our body along the alimentary canal Try this
which begins at the mouth and ends at the anus.
Mouth Eat a small spoonful
Digestion starts in the mouth. Chewing action by the teeth of rice. Chew the rice
(mastication) breaks down large pieces of food into smaller gently for about one
pieces. Chewing also makes the food easier to swallow. The minute. How does it
tongue helps to mix the food with saliva. The saliva contains taste after chewing for
carbohydrase that helps to digest starch into simple sugar. The some time? What has
tongue rolls the food into a ball. The ball of food is then moved happened to the rice?
down to the stomach through the oesophagus.
WB Link Activity 12.6

71Plant and Animal Nutrition

Stomach
The stomach is a muscular organ that secretes gastric
juices, which contain an acid and proteases. The acid
helps the proteases in the digestion of protein. It also kills
microorganisms. The stomach mixes the food with the gastric
juice through a churning action.
Small intestine
In an adult, the small intestine is about 6 to 7 metres long.
It contains the enzymes carbohydrase, protease and lipase.
These complete the digestion of the food into its simplest
forms (simple sugars, amino acids, fatty acids and glycerol).
These are then absorbed into the bloodstream.
Large intestine
In an adult, the large intestine is about 1.5 metres long.
Undigested food, fibre, water, minerals and vitamins pass
into the large intestine. Only water, minerals and vitamins are
absorbed. The rest of the undigested food (waste materials)
is temporarily stored in the rectum before being removed as
faeces through the anus.

How does food move?

Food is digested as it moves along the alimentary canal. The
muscles in the wall contract and relax, producing a wave-
like pattern called peristalsis, which pushes the food down.
Peristalsis allows the food to be mixed with the digestive juices,
while pushing the food along the alimentary canal.

Oesophagus

Food

Stomach

Peristalsis

72 Plant and Animal Nutrition

Absorption of food

Digested food consists of many simple and soluble particles
which move through the walls of the small intestine into
the blood.

Simple sugars, amino acids,
fatty acids and glycerol particles
can get into the blood.

Carbohydrates, proteins, and Blood
fat particles cannot get into the
intestinal wall.

Absorption of food in the small intestine

Quick Check

1. Why should food be digested?
2. Identify the structures of the alimentary canal in the

digestive system.
3. State the function(s) of the stomach and small intestine.
4. How is food moved through the oesophagus to the

stomach?
5. What are the enzymes that help to break down:

a) proteins,
b) carbohydrates, and
c) fats?

73Plant and Animal Nutrition

Summary

Food and Nutrition

used for are digested in the should be eaten
Energy Digestive system
in correct
proportions

Growth through Balanced
Maintaining alimentary canal diet

a healthy • Mouth Which contains may contain
body • Oesophagus enzymes that
• Stomach help to break Food
obtained by • Small down food additives
into simpler
intestine substances cause
• Large • Hyperactivity
• Cancer
intestine
• Rectum
• Anus

Plants contains Proteins Proteins protease Amino acids
through Carbohydrates Starch carbohydrase Simple sugars
Fats lipase Fatty acids + Glycerol
Photosynthesis Fats

Dietary f ibre

Vitamins

Mineral salts

Water

Carbon dioxide + Water Light energy Glucose + Oxygen

Chlorophyll

74 Plant and Animal Nutrition