HBSC 3203

Table of Content
Reading List …………………………………………………………………… i
TOPIC 1 : THE AIR AND RESOURCES AROUND US ………………… 1
TOPIC 2 : METALS …............................................................................ 41
TOPIC 3 : ELECTROLYSIS…………………………..………….………… 66
TOPIC 4 : OXIDATION AND REDUCTION ……………………………… 85
Appendix 1
Appendix 2
TOPIC 5 : SPEED OF CHEMICAL REACTIONS ………….…………… 137
TOPIC 6 : HYDROCARBON COMPOUNDS I …………………………. 172
TOPIC 7 : HYDROCARBON COMPOUNDS II ………………………… 238
Appendix 3
Appendix 4
TOPIC 8 : NATURAL MATERIALS AND MANUFACTURED OR
MAN–MADE MATERIALS …………………………………… 275

Topiicȱ1X TheȱAirȱandȱ
Resourcesȱ
AroundȱUsȱ
LEARNING OUTCOMES
By the end of this topic, you should be able to:
1. Describe the composition of air;
2. Explain the percentage of nitrogen, oxygen and carbon dioxide in the air;
3. Examine the properties of oxygen and carbon dioxide using water and
sodium hydroxide;
4. Discuss the importance of oxygen in respiration and combustion;
5. Describe air pollution, its sources, effects, and steps to control and prevent
air pollution;
6. Examine the different resources on earth and their importance; and
7. Describe the agencies involved in environmental protection and their
approach.ȱ
1

X TOPIC 1 THE AIR AND RESOURCES AROUND US
2
INTRODUCTION
Do you know this song? If you are not familiar with it, this lovely song was sung by Jordin
Sparks, the 2007 American Idol winner. The lyrics describe how important it is to have
someone that you care around you, as important as it is to have air around you.
Air is all around us, wherever we are. We know that even though we cannot see it. In fact,
there is a huge layer of air surrounding the earth. We call this the atmosphere. We use the air
in the atmosphere for a lot of things. Breathing is one of them. Can you name other uses?
Have you ever flown a kite or seen anyone doing so? How does the kite manage to sway in
the sky? The reason is there is air which maintains the kite’s position. The moving air makes
it possible to fly a kite. We will discuss the air further as we study the composition of air and
the properties of oxygen and carbon dioxide.
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ACTIVITY 1.1
Tilt the mouth of an empty bottle in a basin of water.
Answer the following:
(a) Do you see bubbles coming out of the bottle?
(b) Do you hear any bubble sound?
(c) Can you guess what is in the bottle?ȱ
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TOPIC 1 THE AIR AND RESOURCES AROUND US W 3
COMPOSITION OF AIR
Before we learn about the composition of air, let us do this activity. Put out your hand in front
of your face and breathe in deeply. Then, gently blow outward towards your fingers. What do
you feel? Do your fingers feel cool and tingly? I am sure you felt something blowing past
your fingertips. This is commonly referred to as the air.
Our earth is surrounded by a thick layer of air which we call atmosphere. The air is held
around the earth by the force of gravity. This gravity pulls the gas particles towards the earth.
Do you know the composition of the air that we breathe in? In ancient times, people thought
that air was only one substance. Now, we know that the air is actually a mixture of gases.
These gases are nitrogen, oxygen, carbon dioxide and inert gases. The inert gases in the air
include argon, neon, helium, krypton, xenon and methane. Let us look at Table 1.1, which
illustrates the composition of air.
Table 1.1: Composition of Air
Name Symbol Per Cent by Volume
Nitrogen N2 78.084%
Oxygen O2 20.9476%
Argon Ar 0.934%
Carbon Dioxide CO2 0.0351%
Neon Ne 0.001818%
Helium He 0.000524%
Methane CH4 0.0002%
Krypton Kr 0.000114%
Hydrogen H2 0.00005%
Xenon Xe 0.0000087%
Source: CRC Handbook of Chemistry and Physics
1.1
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PERCENTAGE OF GASES IN THE AIR
What are the characteristics of air? Air is colourless, tasteless and odourless. Air supplies the
oxygen necessary for life. Air is also a mixture of gases – nitrogen, oxygen and carbon
dioxide. Do you know that the most abundant gases found in our atmosphere are nitrogen and
oxygen? This is true as nitrogen makes up around 78% of the total atmosphere, oxygen 21%
and carbon dioxide 0.035%. This means when you inhale, you breathe in 78% nitrogen, 21%
oxygen, and 1% argon, with trace amounts of other gases, such as methane, hydrogen,
helium, neon, krypton and carbon dioxide. These percentages of gases are shown in Figure
1.1.
Figure 1.1: Composition of our atmosphere
ACTIVITY 1.2
Try these activities to show your students that there is
air around us.
(a) Ask two students to run along the corridor.
(b) Next, ask them to run again along the same
Corridor, holding a large sheet of card in front of them.
So, which was easier – running with the card or without it? Ask your students to
explain.
1.2
4

However, this does not mean nitrogen will keep on increasing in the atmosphere. It is
constantly being removed or cleansed from the atmosphere. A small amount of nitrogen is
removed by living organisms. Rain and snow also wash nitrogen out of the atmosphere.
As we learnt before, plants consume carbon dioxide. Plants use carbon dioxide in the air for
photosynthesis and release oxygen during the process. This oxygen is later removed from the
air by animals and other life forms. Oxygen is the most important gas in our atmosphere due
to its strong relation with human and animal life. Without it, each of us, and most of the
animals on earth would perish in a matter of minutes. Now, let us conduct an experiment to
find out how much oxygen is in the air. The following is an experiment to find the
percentage of oxygen in the air.
ȱExperimentȱ1.1ȱ
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Objective:ȱ
x To find out how much oxygen is in the air.ȱ
Procedure:ȱ
x Start by pushing in completely one gas syringe.
x Heat up the copper turnings strongly.
x As they are heated, air is passed over them by pushing in one syringe first
and then the other.
x As the reaction happens, you will notice the copper turnings becoming black.
x This is because they have reacted with the oxygen from the air.
x What do you think is the name of this black compound?
x Continue heating until no more copper turnings turns black and the amount of air
in the syringes stays the same.
Result:
x You will find that the amount of air left in the syringes at the end is 79cm3. How
much air has been used up? You will find that this is the amount of oxygen in
100cm3 of air. As you can see, nearly one-fifth of the air is filled with oxygen.
Next, let us do an activity to calculate the exact percentage of oxygen in the air.
Let us start!
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ACTIVITY 1.3
SELF-CHECK 1.1
1. Air is a mixture of gases. State two reasons to support this statement.
2. State the percentage of nitrogen, oxygen and carbon dioxide in the air.
6

PROPERTIES OF OXYGEN AND CARBON DIOXIDE
We know that oxygen and carbon dioxide are two of the most important gases in the air. The
amount of carbon dioxide is very small, about three parts in ten thousand. However, oxygen
comprises 20.94% of the air. We are now going to look into the properties of oxygen and
carbon dioxide. We will look into three matters:
(a) Their solubility in water;
(b) Their reactions with sodium hydroxide; and
(c) The tests for oxygen and carbon dioxide.
Before we discuss further, let us look at the general properties of oxygen and carbon dioxide
first (Table 1.2).
Table 1.2: Seven General Properties of Oxygen and Carbon Dioxide
Properties Carbon Dioxide Oxygen
Features Colourless and odourless Colourless and odourless
Solubility in water More soluble than oxygen Slightly soluble
Solubility in sodium
hydroxide solution
Very soluble Not soluble
Solubility in alkaline
pyrogallol solution
Not soluble Soluble
Lime water reaction
Turns cloudy No effect
Combustion Does not support and does not
burn
Supports but does not burn
pH Acidic Neutral
1.3
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1.3.1 Solublity in Water
We have just learnt the properties of oxygen and carbon dioxide in Table 1.2. Now, let us
look at the difference of solubility of these gases by doing Experiment 1.2.
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Experiment 1.2
Objective:
x To show the solubility of oxygen and carbon dioxide in water.
Procedure:
x Invert two test tubes containing oxygen and carbon dioxide in a beaker of water.
x Watch the rise in the water level. What can you conclude about this experiment?
Result:
x You will notice that in the test tube containing oxygen, a little water enters the test
tube (Figure a). This shows that oxygen dissolves slightly in water.
x However, in the test tube containing carbon dioxide, more water enters the test
tube (Figure b). This shows that carbon dioxide is more soluble in water than
oxygen.
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(a) (b)ȱ
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1.3.2 Reaction with Sodium Hydroxide
What are the reactions of oxygen and carbon dioxide with sodium hydroxide?
Let us find out by doing Experiment 1.3.
Experiment 1.3
Objective:
x To show the reactions of oxygen and carbon dioxide to sodium hydroxide.
Procedure:ȱ
x Invertȱ aȱ testȱ tubeȱ ofȱ oxygenȱ intoȱ aȱȱbeakerȱ ofȱ sodiumȱ hydroxideȱ solutionȱ
(Figureȱa).ȱ
x Removeȱtheȱstopperȱandȱshakeȱtheȱtestȱtubeȱgently.ȱ
x Observeȱtheȱflowȱofȱsodiumȱhydroxideȱsolutionȱintoȱtheȱtestȱtube.ȱ
x Repeatȱtheȱexperimentȱusingȱaȱtestȱtubeȱcontainingȱcarbonȱdioxideȱ(Figureȱb).ȱ
ȱȱȱȱȱȱ
(a) ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ(b)ȱ
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Result:
x Sodium hydroxide solution does not rise in the test tube containing oxygen. This
shows that oxygen is not soluble in sodium hydroxide solution.
x Sodium hydroxide solution rises rapidly in the test tube containing carbon dioxide.
This indicates that carbon dioxide is very soluble in sodium hydroxide solution.
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1.3.3 Tests for Oxygen and Carbon Dioxide
We can test the presence of oxygen by testing it with a burning splinter. As for carbon
dioxide, we will test it with lime water. Look at Experiments 1.4 and 1.5 on how to conduct
these tests.
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Experiment 1.4
Objective:
x To test the presence of oxygen.
Procedure:
x Light up a burning splinter.
x Insert the burning splinter into a test tube containing oxygen (Figure a).
What can you see?
Result
x You will see that the burning splinter will light up (Figure b). The
splinter glows because oxygen supports combustion.
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(a)
(b)
Burning splinter
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Experiment 1.5
Objective:
x To test the presence of carbon dioxide.
Procedure:
x Put lime water into a test tube that has been filled with carbon dioxide gas.
x Close the test tube with a cork. Shake the test tube for a while. What can you see
after that?
Result:
x The lime water will turn cloudy in the presence of carbon dioxide. Carbon
dioxide reacts with lime water to form calcium carbonate, which is insoluble in
water.
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ACTIVITY 1.1
Look at the diagram.
1. Which candle in the diagram takes a longer time to extinguish?
2. What conclusion can you arrive at from this observation?
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SELF- CHECK 1.2
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IMPORTANCE OF OXYGEN
As mentioned earlier, oxygen is a basic element in life. How about its features? It is
colourless, highly reactive and is said to come from water vapour. It turns into a bluish liquid
at a temperature of -183°C.
We are aware that oxygen plays an important role in our lives. Can you name some of its
uses? It is used for breathing, decomposition of organic wastes, the support of aquatic life in
the form of oxygen dissolved by water and creation of energy in living cells.
1.4.1 Respiration
Why do you think oxygen is needed in respiration? Let us find out!
All organisms require energy to carry out all living processes such as growth, reproduction,
response, movement, breathing, digestion and excretion. Energy is stored in the form of
chemical energy in organic substances such as carbohydrates, lipids and proteins. It needs to
be converted into a form of energy which can be readily used by cells. This calls for
respiration as respiration is the chemical breakdown of food to release the energy which is
essential for all living things.
Do you know that respiration is divided into two stages? Let us look at what these two stages
are as shown in Figure 1.2.
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Figure 1.2: Two stages of respiration
1.4
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Now, let us look at the definition of external respiration.
External respiration is a mechanical process of
inhalation and exhalation of air through the
respiratory system.
Can you imagine how this process works? Look at Figure 1.3. During breathing or external
respiration, oxygen is inhaled and carbon dioxide is released
Figure 1.3: Breathing or external respiration
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How about internal respiration? Internal respiration occurs inside the cells and tissues of the
body. Thus, it is often called cell respiration, or tissue respiration. To respire, we need a
constant supply of oxygen. When this oxygen reaches the cells, it combines with glucose (a
sugar which comes from food that has been converted). Energy is then released, together with
waste products of carbon dioxide and water. Respiration, which uses oxygen, is called
aerobic respiration. However, under certain circumstances, energy can be released from food
without oxygen. This process is called anaerobic respiration.
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As a conclusion, we have learnt that the products of respiration are energy, carbon dioxide
and water vapour (Figure 1.4).
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Figure 1.4: The products of cellular respiration
This chemical reaction can be written as:
C6H12O6 + 6O2 6CO2 + 6H2O + Energy
Glucose Oxygen Carbon dioxide Water
SELF-CHECK 6.1
SELF-CHECK 1.3
The following statements are false. Rewrite them to make them true.
1. Respiration and breathing are the same process.
2. Only animals carry out respiration.
3. Acrobatic respiration is the process where energy is made from sugar in the
presence of oxygen.
4. The reactants used in respiration are water and carbon dioxide.
5. The only gas we breathe in is oxygen.
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1.4.2 Combustion
What is combustion? Let us look at what combustion stands for.
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Combustion is the process of burning.
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Here is a simple principle behind combustion. For combustion to occur, fuel, oxygen (air) and
heat must be present together. In other words, combustion takes place when chemicals mix
together and give off heat and light in the form of fire. For example, the charcoal in a
barbecue grill burns because it mixes with oxygen in the air. In Figure 1.5, the fire goes out if
the grill is closed because air cannot reach the coals. Figure 1.6 shows us materials containing
chemicals that burn easily when heated
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Figure 1.5: Charcoal burning in a barbecue grill
Source: World Book Illustration
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Figure 1.6: Materials containing chemicals that burn easily
Source: World Book Illustrationȱ
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Now that you have understood what combustion is, let us carry out an experiment. What gas
do you think is needed for combustion to occur? Yes, oxygen is needed for combustion. So,
how do we conduct an experiment to show that oxygen is needed for combustion? Let us do
Experiment 1.6.
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Experiment 1.6
Objective:
To show that oxygen is needed for combustion.
Procedure:
You need to do this experiment in pairs.
x Get two glass jars of different sizes.
x Light two candles and put each in a jar.
x Mount the candle on a thick cardboard.
x Then seal the jar to ensure that the supply of oxygen is cut off. Observe the flame.
Result:
As the flames consume the oxygen in the jars, the flames will go out. The
candle flame in the bigger jar (A) will burn out last.ȱ
Can you explain what made the flame burn out? The flame uses up oxygen as it burns and
when enough has been used up, the flame goes out.
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SELF-CHECK 1.4
1. Define combustion.
2. List three conditions necessary for combustion to occur.
AIR POLLUTION
1.5
Let us look at Figures 1.7 and 1.8. What do both pictures have in common?
Figure 1.7: Burning forest Figure 1.8: Burning building
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The trees and buildings are on fire. We call this process combustion. Can you name the
products of combustion? In the pictures, you can see smoke, dirt and damage to trees and
buildings. In fact, smoke and dust cause pollution to the environment.
When we talk about air pollution, the images conjured in our minds would be those of smog,
acid rain, chlorofluorocarbons (CFCs) and other forms of outdoor air pollution. However,
pollution also happens inside our homes and other buildings. Every year, the health of many
people is affected by chemical substances found in the air within buildings.
Let us learn more about air pollution. In this subtopic, we will discuss the definition of air
pollution, its sources and effects. We will then discuss the importance of clean air and how to
keep the air clean in order to control and prevent further air pollution. Let us start the topic
with Activity 1.4.
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Let us find out how dirty or clean the air in your classroom is. You will need three sheets
of white paper or cardboard and petroleum jelly. This is how you do it:
x Smear one side of two sheets of paper with petroleum jelly.
x Put the sheets next to each other, with the smeared side up, on a windowsill and
clamp the sheets in place with the closed window.
Take in one of the sheets at the end of one week and see how dirty it looks (compare
it to a clean sheet of paper).
x What can you conclude about this?
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What is air pollution? Do you know that our earth is the only planet we know that has air and
water? That is why (as far as we know) only earth can cater to living creatures. Without air
and water, the earth would be unable to sustain life. We have a diverse community of plants
and animals and they have thrived on this planet for millions of years, sustained by the sun
and supported by the soil, water and air.
We breathe in air which supplies us with oxygen. Oxygen is essential for our body systems to
function. Air consists of 99.9% nitrogen, oxygen, water vapour and inert gases. Our activities
can release substances into the air. Some of these substances can cause problems for humans,
plants and animals. One of the problems is air pollution. How does it occur?
1.5.1 Sources of Air Pollution
Now, let us find out what the sources of air pollution are. As we learnt before, air pollution
occurs when the air contains pollutants. Air pollutants are substances that are released into the
environment. These substances are harmful to us and other living things. There are seven
sources of air pollution as described in Table 1.3.
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ACTIVITY 1.4
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Table 1.3: Seven Sources of Air Pollution
Source Description
1. Natural Sources There are many natural sources of air pollution such as eruption of
volcanoes, biological decay and forest fires caused by lightning strikes.
2. Industrial Activities Our economy is mainly based on manufacturing (especially electronics),
chemical and rubber industries. In order to increase output, industries
increase their normal production. This leads to higher emissions of
organic and inorganic gases, chemicals and dust. Different industries
emit different pollutants. For example, the chemical industry releases
emissions that contain many nitrogen and sulphur compounds while
refineries discharge sulphur dioxide and hydrocarbons. The metal
working industry is partially responsible for the emissions of sulphur
dioxide and large amounts of toxic dust.
3. Development
Activities
Unplanned and uncontrolled development of industrial premises or
zones leads to noise pollution and vibration disturbance. The use of
conventional piling methods and the sound of exhaust fans in factories
are some of the common activities that generate a high sound level.
4. Motor Vehicles Modern societies rely heavily on motorised transportation such as cars,
trucks and railways. Automobiles rely mostly on the burning of fossil
fuels. They not only cause emissions of smoke and dust but are also
responsible for the increase in noise. In 2004, nearly 14 million vehicles
were registered in Malaysia, almost double the number from a decade
earlier. The number will increase in the next few years due to higher
disposable incomes, rural-urban migration and the lack of an efficient
public transport system.
5. Power Generation Most of the energy produced in conventional power plants is by burning
fossil fuels like natural gas, oil and coal. The burning of fossil fuels will
result in the emission of smoke and dust.
6. Everyday Routines Households contribute to air pollution mainly through the use of energy
that is required to run machines and electrical appliances such as
refrigerators. Refrigerators and air conditioners not only consume
energy but also pollute the environment when their coolant fluids
release CFCs into the atmosphere. Chemicals used in houses and
gardens are also sources of pollution as well as toxic waste.
7. Open Burning Some countries practise open burning of older plantations as a method
for re-planting. This results in large amounts of soot particles. These
soot particles can be blown over long distances and are mainly
responsible for the haze that often covers the sky above Malaysia. These
fires can also destroy the rich habitat of flora and fauna.
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Do you realise that even our homes contribute to air pollutants? Find out the causes of air
pollution from our homes (Figure 1.9) and the outdoors (Figure 1.10).
Figure 1.9: Air pollutants inside and outside a house
Figure 1.10: Outdoor air pollutants
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1.5.2 Effects of Air Pollution
There are thousands of air pollutants. However, we are going to focus only on a few
pollutants, including their sources and effects on our health. Let us refer to Table 1.4.
Table 1.4: Pollutants, Their Sources and Effects on Human Health
Pollutant Source Human Health Effect
Particles - Air Particle
Index (API)ȱ
x Internal combustion
engines (e.g. cars and
trucks)
x Industry (e.g. factories)
x Burning wood
x Cigarette smoke
x Bush fires
Long-term exposure is
linked to health problems
such as
x Lung cancer
x Heart disease
x Lung disease
x Asthma attacksȱ
Nitrogen Dioxide (NO2) x Motor vehicles are the
biggest contributors
x Other combustion
processesȱ
Exposure to high levels of
NO2 may lead to:
x Lung damage
x Respiratory disease
x Asthma and respiratory
problems
x Increased mortalityȱ
Sulphur Dioxide Burning of coal and
petroleum in factories and
power-generating stationsȱ
x Breathing
difficulties
x Bronchitis
x Acid rain occurs when
sulphur dioxide
dissolves in rainwaterȱ
Carbon Monoxide (CO) x Burning of hydrocarbon
x Exhaust gases from
motor vehicles
x Cigarette smoke
x Dizziness and headache
x Can cause death if a
large amount is inhaled
Lead (Pb)ȱ x Vehicle exhaust fumes
x Other atmospheric
sources of lead include
waste incineration and
renovation of old
houses (from leaded
paint)ȱ
x Affects children’s learning and
development of their
nervous system
x Affects almost every
organ in the body,
whether it is inhaled or
ingested. Young
children are particularly
susceptible
Smoke Soot Dust x Burning of waste and
fuels by factories
x Forest fires
x Cigarette smoke
x Smoke from vehicles’
exhaust
x Pollutes the environment
x Slows down
photosynthesis
x Damages respiratory
system
x Can cause cancer
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Carbon Dioxideȱ x Burning of rubbish and
fuelsȱ
x Causes greenhouse
effect (increase in
temperature on earth)
Chlorofluorocarbon (CFC)ȱ x Aerosol cans,
refrigerators, air
conditionersȱ
x Depletion of the ozone layer
x Diseases related to
ozone layer depletion
(e.g. cataract, skin cancer)ȱ
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Ask your students to explain the effects of the following pollutants on our health:
x Transportation
x Factories
x Agricultural activities
Present the findings in class.
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Air pollution has consequences to the environment. There are three main consequences of air
pollution to the environment as presented in Table 1.5.
Table 1.5: Three Main Consequences of Air Pollution to the Environment
Consequence ȱ Description
Acidȱrainȱ Acid rain happens when sulphur and nitrogen pollution
from industrial smokestacks combine with moisture in the
atmosphere (see Figure 1.11). The resulting rain is acidic
which destroys natural ecosystems and buildings.
Greenhouseȱeffect The planet’s temperature increases as heat energy from
sunlight is trapped by the gaseous atmosphere. Excess
carbon dioxide and water vapour increase this global
warming effect.
Thinningȱofȱtheȱozoneȱlayer The ozone in the ozone layer is destroyed due to the
presence of chlorine from manmade CFCs and other forces.
The layer is thinning because the ozone is destroyed faster
than it is regenerated by natural forces.
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ACTIVITY 1.5
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Now, let us look at Figure 1.11, which shows the cycle of acid rain.
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Figure 1.11: Acid rain cycle
Source: www.newint.org
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How about the greenhouse effect and depletion of ozone layer? Let us refer to
Figures 1.12 and 1.13.ȱ
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Figure 1.12: Greenhouse effect
Source: www.coolmob.orgȱ
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Figure 1.13: Depletion of ozone layer
Source: www.scienceclarified.com
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What causes the thinning of the ozone layer? What effects does it have on us?
List five things we use in our everyday life which contribute to the thinning of the
ozone layer.
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1.5.3 Step to Prevent Air Pollution
In order to prevent or control air pollution, we have to keep the air clean. Let us look at the
steps to keep the air clean.
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After discussing how important the air is to us and learning the effects of air pollution, let us
think of the ways to keep the air clean. Remember, everybody has the power to make a
difference to the quality of the air and environment. All of us, whether we realise it or not,
contribute to air pollution in one way or another. In order to improve the quality of the air we
breathe in, we must be aware of the activities that can contribute to pollution and take action
against it. We can take action personally, at home or at school, or by doing something with
others in the community.
Now, what actions can we take to keep the air clean? Let us refer to Table 1.6.
Table 1.6: Ways to Keep the Air Cleanȱ
Way Suggestion
Make a difference on the roadȱ x Walk or ride your bike instead of getting a lift in a car.
x Where possible, use public transport instead of riding in
your parents’ car.
x When running errands, combine trips so that you do not use
your car for single purpose trips.
x Drive wisely and do not idle. Save petrol by switching off
the engine even when you are stationary for a while.
x Use non-ozone depleting refrigerant for your car’s air
conditioning system.
x Use unleaded petrol to reduce the amount of lead particles in
the air.
Make a difference at homeȱ x Use household and garden chemicals wisely. Avoid using
CFC-based products.
x Be sure to read labels for proper use and disposal of
products.
x If you purchase a new air conditioning system or heat pump,
purchase one that uses a non-ozone depleting refrigerant.
x Practise wise waste management. Recycle aluminium cans,
glass bottles, plastics, cardboards and newspapers. This will
SELF-CHECK 1.5
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x reduce waste and conserve natural resources.
x Buy products made of recycled content.
x Stop practising open burning.
x Take part in tree-planting activities.
Industrial sectors can make a
differenceȱ
x Practise cleaner production technology.
x Use energy-saving products.
x Carry proper servicing and maintenance on equipment and
machinery used.
x Stop open burning.
x Practice Zero Burning Technique (agricultural sector).
x Reduce the use of pesticides that are non-environmental
friendly (agricultural sector).
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Lastly, let us look at the steps needed to control and prevent air pollution. Preventing and
controlling air pollution require the efforts of people from all walks of life. Previously, we
mentioned what we and also industrial sectors can do to keep the air clean. Now, we will
discuss the steps required by the relevant authorities to control and prevent air pollution.
The steps are:
(a) Implementation of law: Malaysia has implemented the Environmental Quality Act
(EQA) 1974. This Act was enacted to prevent, abate, control pollution and enhance
the quality of the environment.
(b) Inspection and enforcement visits. These are carried out to industrial premises to
ensure that industrial sectors comply with the Environmental Quality Act 1974.
(c) Conducting roadside inspections on motor vehicles.
(d) Conducting aerial and ground surveillance on pollution sources.
(e) Daily monitoring of air quality.
(f) Conducting awareness programmes to educate public on the need to protect the
environment.
Do you know that there is a simple way to measure the air pollution level? The simple way is
the Air Pollution Index (API). This index describes the air pollution levels to provide timely
information about air pollution to the public. Table 1.7 shows the API status indicator used in
Malaysia.
ȱ
25

26
Table 1.7: Malaysian API Status Indicator
APIȱ Statusȱ
0Ȭ50ȱ Good
51Ȭ100ȱ Moderateȱ
101Ȭ200ȱ Unhealthyȱ
201Ȭ300ȱ Veryȱunhealthyȱ
301Ȭ500ȱ Hazardousȱ
Aboveȱ500ȱ Emergencyȱ
ȱ
You can get more on the daily readings of the API by visiting
http://www.doe.gov.my/index.php?option=com_content&task=view&id=188&
Itemid=370&lang=en
1. What is air pollution? Name five air pollutants.
2. List the pollutants which affect the environment. Describe one pollutant
and what it does to the environment.
3. Name three pollutants from a factor which affects a person’s health.
4. Why must we keep our air clean? How do we know the air is clean?
5. Name two substances which can cause acid rain. State the effects of acid
rain to our health.
ȱ
Let us conduct an activity to reduce air pollution in your school.
Hold a class discussion on air pollution. Discuss the main sources of air
pollution in the school area. Suggest possible ways and activities to
reduce air pollution in your school. Carry out the activities suggested.
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
ACTIVITY 1.6
SELF-CHECK 1.6
26

VARIETY OF RESOURCES ON EARTH
1.6
ȱ
The Carson Fall in Mount Kinabalu, Malaysia is an
example of undisturbed natural earth’s resource.
Waterfalls provide spring water for humans, animals
and plants for survival and also a habitat for hydro
organisms. The water current can be used to turn
turbines for hydroelectric generation.
ȱȱȱȱ
ȱȱȱȱȱȱFigure 1.14: The Carson Fall in Mount Kinabalu
Source: http:/ www. Google.wikipedia.comȱ
1.6.1 Different Resources on Earth
Who need resources? Why do we need resouces? What types of resources do we have?
Human beings, animals and plants need food, water, air and shelter in order to survive. The
earth has the resources needed to sustain life. The resources are air, water, soil, minerals,
fossil fuels and living things.
1.6.2 Important of Earth’s Resources
The earth is rich in natural resources that we use daily. These resources are any valuable
material of geologic origin that can be extracted from the earth. It is nearly impossible to
cease consuming natural or geologic resources altogether. Here are just a few examples of
things you commonly use, but probably do not think about:
x A pencil uses zinc and copper (to make the brass), petroleum for the eraser, iron (in
the machinery to make the pencil), pigments, clay and graphite. The only renewable
resource in your pencil is the wood!
x Your jeans, although they may be almost all cotton, are usually blended with
petroleum-based synthetic fibres to cut down on shrinking.
x Eye glasses and windows are made of quartz sand and petroleum.
x Dental fillings are made of mercury and silver.
x Videotapes are made of vinyl, iron and chromium.
27

28
Please refer to Table 1.8 to learn more about the impotance of earth’s resources.
Table 1.8: The Importance of Earth’s Resources
Types of
Earth
Resources
The Importance of Earth’s Resources
Airȱ x Air is needed by all living things to survive.
x The atmosphere is a layer of air that envelops the earth.
x Air is a mixture of gases. Air contains gases such as oxygen, nitrogen and
carbon dioxide.
x Oxygen and carbon dioxide are two very important gases that support life
on earth.
a. Oxygen
i. Used for respiration by living things
ii. Used in combustion of materials
iii. Used in industries
iv. Released during photosynthesis.
b. Carbon dioxide
i. Used by green plants to carry out photosynthesis
ii. Used in fire extinguishers
iii. Released during respiration and combustionȱ
Waterȱ x Water covers a total of about three quarters of the earth.
x The sources of water are oceans, seas, rivers, lakes, rainfall and ground
water.
x Importance of water
a. To animals/humans
i. It provides a medium for chemical process and body
metabolism;
ii. It is the main component of the blood;
iii. It transports nutrients to all cells in the body;
iv. It carries excretory products to the kidneys for excretion; and
v. It helps to control the body temperature.
b. To plants
i. It helps to maintain the turgidity of plant cells;
ii. It is used in photosynthesis;
iii. Need for the germination of seeds;
iv. Dissolves minerals slats in the ground for absorption by the roots of
plants;
v. Helps to support aquatic plants; and
vi. Cools down the plants (transpiration).
28

Soilȱ x Soil refers to the outer layer of the earth.
x Soil contains mineral matter, organic matter, air and water.
x The soil organic matter includes:
· Organic litter such as fallen leaves, twigs, fruit, animal dropping, etc.
· Humus formed from the composition of organic litter.
· Microorganisms living in the soil.
x Air and water are found in pore spaces between the soil particles.
x The presence of air and water in the soil makes it a natural habitat for
various types of plants and animals.
x Importance of soil:
· Source of minerals and fossil fuels;
· Source of clay for making pottery;
· Source of sand for making glass and cement;
· Base for agricultural activities; and
· Foundation for construction of houses, buildings, roads and other
structures.ȱ
Livingȱ
Thingsȱ
i. Flora and fauna (plants and animals) are also natural resources that
sustain life.
ii. Plants and animals are resources needed by human beings.
iii. We can obtain food, fuel, materials for making clothes and building
materials from plants and animals.
iv. Green plants can make their own food by carrying out photosynthesis.
v. Animals are not able to make their own food.
vi. Some animals such as giraffes and elephants feed on plants.
vii. Some animals such as tigers and snakes feed on other animals.
viii. Aquatic plants and animals are also important resources for sustaining
life.ȱ
Mineralȱ i. Minerals are inorganic substances found naturally on land and in seas
or oceans.
ii. Examples of minerals are feldspar, quartz, iron, zinc, aluminium, tin,
silver and gold.
iii. Some minerals such as aluminium and iron are mined because they
can be used as raw materials in various industries.
There are two types of earth’s resources – renewable and non-renewable resources.
Earth’s resources that can be replaced and reused by nature are termed renewable. Natural
resources that cannot be replaced are termed non-renewable. Renewable resources are
replaced through natural processes at a rate that is equal to or greater than the rate at which
they are used, and depletion is usually not a worry.
Some common examples include:
x Air (wind);
x Fresh water;
x Soil;
29

30
x Living organisms (trees); and
x Sunlight.
Non-renewable resources are exhaustible and are extracted faster than the rate at which they
formed. Some common examples are:
x Fossil fuels (coal, oil, natural gas);
x Diamonds and other precious gems and minerals; and
x Types of metals and ores.
1.6.3 Preservation and Conservation of Earth’s Resources
With the increased use of virtually all natural earth’s resources, there is concern that
resources will be exhausted and that others will not be able to use them in the future. Can you
imagine a world without clean water, clean air, sustainable land or living oceans?
Our natural resources exist in a delicate balance and are vulnerable to environmental changes.
That is why it is important that we all do our part to conserve, preserve and care for the
earth’s resources and protect the environment that sustains us with food, fuel, shelter and
medicine.
Because of the severe impact that we impose on the land, air, and water, preservation and
conservation has become increasingly important. Let us check the meaning of preservation
and conservation.
Preservation is to keep and maintain what you have
Conservation is to spend or use sparingly
30

ACTIVITY 1.7
1.6.4 Recycling of Materials
ȱ
“Reduce, Reuse, Recycle”
Figure 1.15: Reduce, Reuse and Recycle
The symbol and the phrase above are very common. Do you know its meaning?
Reduce : Do not use a resource if there is an alternative (walking versus driving).
Reuse : Use a resource again without changing it or reprocessing it; use glassware
as opposed to paper plates and Styrofoam.
Recycle : Reprocess a resource so that the materials can be used in another item.
People can recycle just about anything from cardboard to old shoes!
ȱȱȱȱȱȱ
Discuss in a group of four to find out the meaning of preservation and
conservation in terms of natural earth’s resources. Please visit the following
websites to get more information.
http://www.ecoca.ro/meteo/tutorial/Sustainability/Older/Conservation_and_Pre
servation.html
http://feelfriendly.com/information-preservation-conservation.html
31

32
SELF-CHECK 1.7
Please observe the picture given.
Identify the materials that can be
recycled.
Waste
Products
Solid Waste Medical
Waste
Hazardous
Waste
ȱȱ
ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱ
WASTE PRODUCTS
ȱ
1.7
“Wastes are substances or objects which are disposed of or are intended to be
disposed of or are required to be disposed of by the provisions of national law”
Source: http://wikipedia.google.com
1.7.1 Sources and Types of Waste Products
Figure 1.16: Three types of waste
Source: Von ( 2004)
There are various sources of waste such as domestic sources, commercial sources, industrial
sources, clinic or biomedical sources, mineral sources, agricultural sources and nuclear
sources. Table 1.9 shows a breakdown of common waste types and its sources.
32

Table 1.9: Common Sources and Types of Waste Products
Source Typical Waste Generators Types of Solid Wastes
Residential Single and multi-family
dwellings
Food wastes, paper, cardboard, plastics,
textiles, leather, yard wastes, wood,
glass, metals, ashes, special wastes (e.g.
bulky items, consumer electronics, white
goods, batteries, oil, tyres), and
household hazardous wastes
Industrial Light and heavy
manufacturing fabrication,
construction sites, power and
chemical plants
Housekeeping wastes, packaging, food
wastes, construction and demolition
materials, hazardous wastes, ashes,
special wastes
Commercial Stores, hotels, restaurants,
markets, office buildings, etc
Paper, cardboard, plastics, wood, food
wastes, glass, metals, special wastes,
hazardous wastes
Institutional Schools, hospitals, prisons,
government centres
Paper, cardboard, plastics, wood, food
wastes, glass, metals, special wastes,
hazardous wastes
Construction
and
Demolition
New construction sites, road
repair, renovation sites,
demolition of buildings
Wood, steel, concrete, dirt, etc
Municipal
Services
Street cleaning, landscaping,
parks, beaches , other
recreational areas, water
and wastewater treatment
plants
Street sweepings, landscape and tree
trimmings, general wastes from parks,
beaches, and other recreational areas,
sludge
Process Heavy and light
manufacturing, refineries,
chemical plants, power
plants, mineral extraction
and processing
Industrial process wastes, scrap
materials, off specification products,
slag, tailings
Agriculture Crops, orchards, vineyards,
dairies, feedlots, farms
Spoiled food wastes, agricultural wastes,
hazardous wastes (e.g. pesticides)
33

34
1.7.2 Pollution Caused by Waste Products
ȱȱȱȱȱȱȱȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱFigureȱ1.17:ȱȱDeadȱfishȱcausedȱbyȱwaterȱpollutionȱ
Source: Image Google.com
Many things can cause water pollution but most water pollution is caused by waste products
from humans. Types of waste products that can pollute our water are sewage drainage into
our water cycle, oil from vehicles, oil spills, fertilisers from crops. Rubbish dumps also can
run into our water system when it rains.
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
Figure 1.18: Water Pollution
Source: http://google.image.com
ȱȱȱȱȱ
Do you think why all the
fish in Figure 1.17 were
dead?
34

ȱȱȱ
ȱȱ
SELF-CHECK 1.8
Observe Figure 1.18.
Identify the types of waste products that cause water pollution.
Do You Know?
Waste products (Figure 1.19) also can cause land pollution and air pollution. Land
pollution is caused by an excessive amount of trash going into our landfills. When too
much trash is in our landfills, it can cause water pollution over time by getting in our
water cycle. Another form of land pollution is littering.
Figure 1.19: Solid waste products
Source: http://google.image.com
1.7.3 Environmental Protection
Environmental protection is a practice of protecting the natural environment on individual,
organisational or governmental levels, for the benefit of both the natural environment and
humans. Discussion concerning environmental protection often focuses on the role of
government, legislation and law enforcement. Protecting the environment is a responsibility
of all people.
35

36
(a) Government Organisations’ Involvement
i. Environmental Quality Act, 1974 (Act 127)
An Act relating to the prevention, abatement, control of pollution and enhancement
of the environment:
x Part IV – Prohibition and control of pollution
x Section 22: Restrictions on pollution of the atmosphere
x Section 23: Restrictions on noise pollution
x Section 24: Restrictions on pollution of the soil
x Section 25: Restrictions on pollution of inland waters
x Section 27: Prohibition of discharge of oil into Malaysian waters
x Section 29: Prohibition of discharge of wastes into Malaysian waters
x Section 34: Report on impact on environment resulting from prescribed
activities
ii. Incorporate Department of Environment (DOE) within the Ministry of Science,
Technology and Environment (MOSTE)
x In charge with environmental administration
iii. Incorporate an environmental policy aimed at integrating environmental concerns
into development planning. For example:
x The Seventh Malaysian Plan (1996-2000) states that the objectives of
Malaysia’s national environmental policies are to achieve a clean, safe and
healthy living environment for current and future generation and to promote
lifestyles and modes of production and consumption consistent with the
principles of sustainable development.
(b) Non-governmental Organisation’s Involvement
x Dissemination of environmental information through the Environmental
Management and Research Association of Malaysia (ENSEARCH)
(c) Environmental Education in the School Syllabus
Environmental education will make our citizens aware of the environmental
problems and equip us with knowledge to overcome the problems.
SELF-CHECK 1.9
Find out the involvement of international agencies in
Malaysia’s environmental protection.
36

x The air is actually a mixture of gases. These gases are nitrogen, oxygen, carbon
dioxide and inert gases. The inert gases in the air include argon, neon, helium,
krypton, xenon, methane and xenon.
x Under properties of oxygen and carbon dioxide, we look into three matters, namely,
the solubility in water, reactions with sodium hydroxide and the tests for oxygen and
carbon dioxide.
x Oxygen plays an important role in our lives. We use oxygen for breathing,
decomposition of organic wastes, supporting aquatic life in the form of oxygen
dissolved by water and creation of energy in living cells.
x Airȱ pollutionȱ affectsȱ ourȱ healthȱ andȱ theȱ environment.ȱAirȱ pollutionȱ occursȱ
whenȱtheȱairȱcontainsȱgases,ȱdust,ȱfumesȱorȱodourȱinȱharmfulȱamounts.ȱ
x Our natural resources include air, water, soil, minerals, fossil fuels, plants and
animals. Each of these resources is important to us in their own ways.
x Conservation is the sustainable use of our natural resources. Preservation is keeping
natural resources in their current state, untouched by humans.
x Recycleȱ isȱ theȱ processȱ ofȱ reprocessȱ aȱ resourceȱ soȱ thatȱ theȱmaterialsȱ canȱ beȱ
usedȱinȱanotherȱitem.ȱȱȱ
ȱ
x Wasteȱareȱsubstancesȱorȱobjects,ȱwhichȱareȱdisposedȱofȱorȱareȱintendedȱtoȱbeȱ
disposedȱofȱorȱ areȱ requiredȱ toȱbeȱdisposedȱofȱbyȱ theȱprovisionsȱofȱnationalȱ
law.ȱItȱcanȱbeȱdividedȱintoȱthree,ȱsolidȱwaste,ȱmedicalȱwasteȱandȱhazardousȱ
waste.ȱ
ȱȱȱȱȱȱȱȱ
x Environmentalȱprotectionȱcanȱbeȱdoneȱbyȱtheȱgovernment,ȱnonȬgovernmentalȱ
organisations,ȱ internationalȱ agenciesȱ andȱ nationalȱ citizensȱ throughȱ
introducingȱenvironmentalȱeducationȱinȱtheȱschoolȱsyllabus.ȱ
ȱȱȱȱȱȱȱ37

38
ȱ
Air
Air Pollution Index (API)
Carbon dioxide
Chlorofluorocarbon (CFC)
Combustion
Conservation
Environment
External respiration
Global warming
Greenhouse effect
Internal respiration
Land pollution
Natural resources
Oxygen
Preservation
Products
Recycle
Respiration
Waste product
Water pollution
ȱ
ȱ
ȱ
Conoley, C., & Hills, P. (2002). Collins advance science chemistry (2nd ed.). UK: Collins
Educational.
Environmental Quality Act 127. (1974). Retrieved from
https://www.elaw.org/system/files/MalaysiaEQA1974_0.pdf
Gallagher, R. M. (1997). Complete chemistry. UK: Oxford University Press.
Milner, B., Martin, J., & Mills, J. (2002). Core chemistry. UK: Cambridge University Press.
Nivaldo, J. T. (2000). Chemistry in focus (2nd ed.). USA: Thomson.
South Carolina Geological Survey. (2005). Earth’s natural resources and human impacts.
Retrieved from ftp://ftpdata.dnr.sc.gov/geology/Education
Von, L. L. (2004). Case study on the management of waste materials in Malaysia. Forum
Geoökol, 15(2), 7.
Zumdahl, S. S. (2004). Introductory chemistry: A foundation (5th ed.). New York: Houghton
Mifflin.
38

Topiicȱȱ2XMetals
LEARNING OUTCOMES
Byȱtheȱendȱofȱthisȱtopic,ȱyouȱshouldȱbeȱableȱto:
1. Describeȱtheȱphysicalȱpropertiesȱofȱmetals;ȱ
2. ȱDifferentiateȱtheȱstructuresȱofȱmetalsȱandȱalloys;ȱ
3. ȱDescribeȱtheȱchemicalȱreactionsȱofȱmetals;ȱ
4. ȱIdentifyȱtheȱorderȱofȱreactivityȱofȱmetals;ȱ
5. ȱDescribeȱtheȱmethodȱofȱextractionȱofȱironȱandȱaluminium;ȱandȱ
6. ȱDiscussȱtheȱusesȱofȱmetals.ȱ
X INTRODUCTION
Figure 2.1: Gold and copper coins
Source: editmentor.wordpress.com
41

X TOPIC 2 METALS
2
Have you ever seen coins such as the ones in Figure 2.1? Gold and copper were the
first metals discovered in the earth, since 6,000BC. Gold and copper coins have been
used since ancient civilisation. Gold articles were found extensively in antiquity
mainly as jewellery such as bracelets and rings. The symbol for gold is Au from the
latin aurum meaning “shining dawn”. The use of copper in antiquity was of more
significance than gold as the first tools, implements and weapons were made from
copper. The symbol for copper is Cu and comes from the latin cuprum meaning “from
the island of Cyprus”.
Currently, there are 86 known metals. Scientists have categorised metals into three
groups – alkali metals, alkali earth metals and transition elements. You can explore the
names and symbols of all known metals in the Periodic Table of the Elements.
2.1
SELF-CHECK 2.1
1. Name three metals in a group of alkali metals.
2. Name two metals in a group of alkali earth metals.
3. Name two common metals in transition elements.
PHYSICAL PROPERTIES OF METALS
Metals consist of positive ions embedded in moving clouds of electrons (Figure 2.2).
The negatively charged electrons attract all the positive metal ions and bond them
together with strong electrostatic forces of attraction as a single unit called metallic
bond.
ȱ
Figure 2.2: Metals consist of positive ions surrounded by a cloud of electrons
42

TOPIC 2 METALS W 3
2.1.1 Structures of Metals and Alloys
Pure metals have the following properties;
x They usually have high melting and boiling points. This is due to the strong
attraction between the positive metal ions and the mobile clouds of electrons.
x They conduct electricity due to the mobile electrons (electrons cloud) within
the metal structure. When a metal is connected in a circuit, the electrons move
towards the positive terminal.
x They are malleable and ductile. If a force is applied to a metal, rows of ions
can slide over one another. They reposition themselves and the strong bonds
re-form as shown in Figure 2.3.
Figure 2.3: The positions of the positive ions in a metal before and after a
force has been applied
[Source:ȱhttp://www.chemȬisȬ
try.org/materi_kimia/struktur_atom_dan_ikatan/jenis_struktur_atom/s
truktur_logam/]
x They have high densities, as the atoms are arranged in order and closely
packed together as can be seen in Figure 2.4.
Figure 2.4: Arrangement of ions in a metal
[Source: http://martinmm.wiki.manheimcentral.org/84]
43

X TOPIC 2 METALS
4
Different metals show different types of packing and in doing so they produce the
arrangement of atoms shown in Figure 2.5.
ȱȱȱȱȱ
ȱ
ȱȱȱȱȱȱ
ȱ
ȱ
Figure 2.5: Relating different structures to the density of metal
[Source:
http://www.substech.com/dokuwiki/doku.php?id=metals_crystal_structure]
Alloys are a mixture of;
x Two or more metals (for example, brass is an alloy of zinc and copper); or
x A metal and non-metal (for example, steel is an alloy of iron and carbon).
Figure 2.6 shows the alloy structure. The blue circles represent atoms of metal A and
the white circles are atoms of metal B which is added to make the alloy. These
different atoms give the alloy different physical properties from that of the pure metal.
ȱȱȱȱȱȱȱȱȱȱ
Figureȱ2.6:ȱStructureȱofȱanȱalloyȱ
[Source:ȱhttp://www.chem.qmul.ac.uk/surfaces/scc/scat6_4.htm]ȱ
ȱ
Atom of metal A
Atom of metal B
44

TOPIC 2 METALS W 5
Alloys are formed by mixing the molten substances thoroughly. But why make alloys?
The reasons why alloys are made are:
(a) To increase the strength and hardness of a pure metal. The presence of the
2.2
atoms of other elements disrupts the orderly arrangement of the pure metal.
The layers of metal atoms are prevented from sliding over one another easily.
This makes alloys stronger and harder than pure metals.
(b) To increase the resistance to corrosion of a pure metal. Alloying can prevent
metals from corrosion. This is because alloying helps to prevent the formation
of oxide layer on the surface of the metal (We will discuss the reaction of
metals in subtopic 2.2).ȱ
(c) To improve the appearance of a pure metal. Alloying helps to keep the metal
maintain the glossy nature of the surface as it prevents the formation of the
metal oxide.
Table 2.1 shows some of the more common alloys with their composition.
ȱ
Table 2.1: Composition of common alloys
[Source: Ryan (2001)]
Alloy Composition
Brass 65% copper, 35% zinc
Bronze 90% copper, 10% tin
Cupro-nickel 30% copper, 70% nickel
Duralumin 95% aluminium, 4% copper,1% magnesium, manganese and
iron
Magnalium 70% aluminium, 30% magnesium
Pewter 30% lead, 70% tin, a small amount of antimony
Solder 70% lead, 30% tin
CHEMICAL PROPERTIES OF METALS
The metals in ores are chemically bonded to other elements. So how can we extract
the metals? To answer this, we must understand the Reactivity Series of metals. In
the Reactivity Series, the most reactive metals are at the top. The less reactive ones are
at the bottom. We can start putting the metals in order by looking at their actions with
heat, water and dilute hydrochloric acid.
45

X TOPIC 2 METALS
6
2.2.1 Chemical Reaction of Metals with Heat
Conduct Experiments 2.1 and 2.2 to judge the reactivity by putting the metals into
competition with each other. In these two experiments, the metals will “fight” each
other to “win their prize” which is oxygen. The more reactive metal will win the
fight.
ȱ
Experiment 2.1
1. Mix a spatula of iron fillings and copper oxide
in a test tube. Heat the mixture strongly
x Is there a reaction? Look for a red glow
spreading through the mixture.
2. When the tube has cooled, empty it into a dish.
x Can you see any brown copper metal left?
Copper starts off with the oxygen in copper oxide. However, iron is more reactive, so
it takes the oxygen away from copper. We say that iron has displaced (“kicked out”)
the copper.
Copper oxide + iron Æ iron oxide + copper
CuO(s) + Fe(s) Æ CuO(s) + Cu(s)
This is a displacement reaction. It shows us that iron is more reactive than copper.
ȱ
SELF CHECK 2.2
In Experiment 2.1, what do you expect will happen if we change:
x copper oxide with iron; and
x iron with copper?
Will there be any reaction? Why?
There actually will not be a reaction between iron oxide and copper because copper is
less reactive than iron.
46

TOPIC 2 METALS W 7
You can now try some other displacement reactions as in Experiment 2.2.
ȱȱ
ȱ
ȱȱ
ȱ
ȱȱȱȱ
Experiment 2.2
x Try heating the mixtures of metals and oxide
shown in the table:
x Look for any signs of reaction. Tick (—) in the
“Reaction Table” if there is a reaction.
(Be careful when looking for signs of reaction.
Zinc oxide turns yellow when you heat it by
itself. It turns white again when it cools down).
x Write word equations for the reactions you
have ticked)
Metal/
Metal
oxide
Zinc
oxide
Zinc
Iron
Copper
Magnesium
Reaction Table
2.2.2 Chemical Reaction of Metals with Water
Iron
oxide
Copper
oxide
You have already seen how the action of heat with metals in the displacement
reaction. Now, you can arrange the order of the reactivity of metals iron, zinc, copper
and magnesium:
i. Magnesium
ii. Zinc
iii. Iron
iv. Copper
We can also judge reactivity by observing the metal’s reaction with water. Let us look
at the reaction of lithium, sodium and potassium with water.
Experiment 2.3
1. Put water in three different glass basins.
2. Drop small pieces of
x Lithium in basin 1
x Sodium in basin 2
x Potassium in basin 3
3. Collect the gas given off as shown;
x Test the gas with a lighted splint
4. Test the solution formed with red litmus
paper.
x Is the solution left acidic or alkaline?
From Experiment 2.3, you can observe that lithium moves slowly on the surface of the
water, while sodium melts to become a small sphere, move rapidly and randomly on
47

X TOPIC 2 METALS
8
the water surface with a hissing sound as it reacts. Potassium gets so hot that it lights
the hydrogen gas that water gives off. It burns with a lilac flame, move very rapidly
and randomly on the water surface with a hissing and popping sound. The colourless
solution formed turns red litmus paper to blue.
When red litmus paper turns to blue,
the solution formed is an alkaline!
The chemical equation for the reaction of lithium with water is as follows:
Lithium + Water Æ Lithium hydroxide + Hydrogen
2Li(s) + 2H2O (l) Æ 2LiOH (aq) + H2 (g)
SELF-CHECK 2.3
Write the word and symbol equations for sodium and potassium
reacting to water.
In the case of magnesium, this metal normally reacts slowly with water. But we
can speed up the reaction by heating up the water to make steam as in Experiment
2.4.
Experiment 2.4
1. Heat the magnesium strongly.
Every now and again, switch the
flame briefly to the ceramic wool
to make a steam.
2. As the reaction starts, the gas
given off can be lit at the end of
the tube.
x Can you name the gas?
The magnesium reacts strongly with the steam. It leaves white magnesium oxide in
the test tube. Hydrogen gas is given off.
48

TOPIC 2 METALS W 9
Magnesium + Steam Æ Magnesium oxide + Hydrogen
Mg (s) + H2O (g) Æ MgO(s) + H2 (g)
The oxygen atom in H2O has “swapped partner”! It start off with hydrogen, but ends
up with magnesium.
Table 2.2 gives the different observations when metals react with water and steam.
Table 2.2: Reaction of metals with water and steam
T
a
b
l
e
2
.
2
Metals Reaction with Water Reaction with Steam
Potassium
Sodium
Lithium
Calcium
Fizz, giving off hydrogen gas and
leaving an alkaline (hydroxide)
solution.
Explode
Magnesium
Aluminium
Zinc
Iron
Very slow reaction.
(Aluminium is protected by a layer
of aluminium oxide on its surface).
React, giving off hydrogen gas and
forming the metal oxide.
2.2.3 Chemical Reaction of Metals with Diluted
Hydrochloric Acid
Another simple way to judge the reactivity of metals is to compare the reaction with
diluted acid. Metals will react quicker with diluted acid compared to water especially
the metals below calcium in Table 2.2.
Conduct Experiment 2.5 to compare the reactivity of metals when react with dilute
hydrochloric acid.
Experiment 2.5
1. Clean the metals with sand-paper.
2. Set up the boiling tube as shown:
x Can you see bubbles?
(If you see no bubbles, you can warm the
tube gently in a beaker of hot water)
3. Record your results in a table.
(Do your results agree with the order in
Table 2.3 ?)
Notice that copper does not react with hydrochloric acid. However, the other metals
tested do react. For example, magnesium:
49

X TOPIC 2 METALS
10
Magnesium + Hydrochloric acid Æ Magnesium chloride + Hydrogen
Mg (s) + 2HCl (aq) Æ MgCl2 (aq) + H2 (g)
Table 2.3: Reaction of metals with dilute hydrochloric acid
Metals Reaction with Dilute Hydrochloric Acid
x Calcium
x Magnesium
x Aluminium
x Zinc
x Iron
Fizz, giving off hydrogen gas.
(Aluminium is protected by a tough layer of oxide on
its surface)
x Tin
x Lead
Gives off hydrogen very slowly .
(The acid needs to be warmed up)
x Copper
No reaction.
SELF CHECK 2.4
Write word equations for the reactions of calcium, aluminium, zinc,
iron, tin and lead with dilute hydrochloric acid.
ACTIVITY 2.1
Discuss why we never add potassium, sodium or lithium to acid.
2.2.1 Order of Reactivity of Metals
Now, we can form the Reactivity Series of metals according to the reactivity of metals
based on the metals’ reaction to heat, reaction to water and reaction to diluted
hydrochloric acid (Figure 2.7).
50

TOPIC 2 METALS W 11
ȱȱȱȱȱȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figure 2.7: Reactivity series of metals
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
K Potassium
Na Sodium
Li Lithium
Ca Calcium
Mg Magnesium
Al Aluminium
Zn Zinc
Fe Iron
Sn Tin
Pb Lead
Cu Copper
Ag Silver
Au Gold
Pt Platinum
Most reactive
Least reactive
ACTIVITY 2.2
Figure shown is a message from
the Lonely Hearts section of the
‘Zoo of the World’. Can you come
up with your own mnemonic
sentence to help you remember
the Reactivity Series?
51

X TOPIC 2 METALS
12
2.3
EXTRACTION OF IRON AND ALUMINIUM
ȱ
In the earlier sub-topic, we learned about the Reactivity Series. We will now look at
how to get metals from their ores. This includes iron, which is the most widely used of
all metals. Figures 2.8 and 2.9 show iron ore and the mining of iron ore.
2.3.1 Extraction of Iron
Figure 2.8: Iron ore, haematite
[Source: http://www.e-rocks.com/Products.aspx?action=showproduct&id=107003]
Figure 2.9: Mining of iron ore in Karnataka
[Source: http://khanija.kar.ncode.in/SitePages/EAuctionData.aspx]
52

TOPIC 2 METALS W 13
Carbon is important in the extraction of iron. Carbon is a non-metal, but we can put it
into our Reactivity Series of metals. It is placed in between aluminium and zinc. This
means that carbon can displace any metal below aluminium in the Reactivity Series
(Figure 2.10).
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
K Potassium
Na Sodium
Li Lithium
Ca Calcium
Mg Magnesium
Al Aluminium
CARBON
Zn Zinc
Fe Iron
ȱ
Sn Tin
ȱ
Pb Lead
ȱ
ȱ
Cu Copper
ȱ
Ag Silver
ȱ
Au Gold
ȱ
ȱ
Pt Platinum
ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱFigureȱ2.10:ȱTheȱpositionȱofȱcarbonȱinȱtheȱReactivityȱSeriesȱ
ȱ
We get carbon from coal. Coal is cheap and there is plenty of it at present. We use
coke (a cheap form of carbon which is made from coal) as one of the raw materials
besides iron ore (mainly haematite- iron(III) oxide) and limestone (to get rid of sandy
waste) in the process of extracting iron. We use blast furnace to get the iron from its
ore. Figure 2.11 shows the diagram of blast furnace used to extract iron.
Reactions in the blast furnace
x The coke (carbon) reacts with oxygen in the hot air to make carbon oxide.
C(s) + O2(g) Æ CO2 (g)
x This carbon dioxide reacts with more hot coke to produce carbon monoxide
gas.
CO2 (g) + C(s) Æ 2CO(g)
Carbon cannot be used to
extract the more reactive
metals
These metals can be
extracted using carbon
53

X TOPIC 2 METALS
14
x The carbon monoxide then reacts with iron oxide to get iron.
Fe2O3(s) + 3CO(g) Æ 2 Fe(l) (s) + 3CO2 (g)
At the high temperature (up to 1900°C) in the furnace, the iron is in molten form
(liquid). So, it sinks to the bottom of the furnace. The iron then will run off into
mould. The molten slag floats to the top of the iron. The slag is tapped off, cooled and
used for making roads.
Figure 2.11: The blast furnace
[Source: http://images.yourdictionary.com/blastȬfurnace]
2.3.2 Extraction of Aluminium
Figure 2.12: Aluminium ore, bauxite
[Source: http://www.greenerȬ
industry.org.uk/pages/aluminium/aluminium_4PMsummary.htm]
54

TOPIC 2 METALS W 15
As shown in the Reactivity Series (refer Figure 2.10), the position of aluminium is
before carbon. This means aluminium is more reactive than carbon, so carbon cannot
be used to extract aluminium. So, how do we extract aluminium from its ore, bauxite,
which contains aluminium oxide, Al2O3?
Reactive metals can only be extracted from
their ores by electrolysis!
ȱ
ȱ
2.3.3 Extraction of Aluminium – Electrolysis of Aluminium
Oxide
ȱ
Figure 2.13 shows the electrolytic cell used for the extraction of aluminium.
Figure 2.13: Extraction of aluminium
[Source: http://www.meritnation.com/askȬanswer/question/explainȬtheȬ
processȬofȬextractionȬofȬaluminiun/metalsȬandȬnonȬmetals/2230314]
x Aluminiumȱ oxideȱ isȱmixedȱwithȱ cryolite,ȱNa3AlF6,ȱ toȱ lowerȱ theȱmeltingȱ
pointȱofȱaluminiumȱoxideȱ(2045°C)ȱtoȱaboutȱ900°C.ȱ
x Blocksȱofȱcarbonȱactȱasȱtheȱanodeȱwhileȱtheȱcarbonȱliningȱofȱtheȱcellȱactsȱasȱ
theȱcathode.ȱ
x Atȱ theȱ cathode,ȱ theȱ aluminiumȱ ionsȱ areȱ dischargedȱ toȱ formȱ aluminiumȱ
metal.ȱ
Al3+(l)ȱȱȱ+ȱȱȱ3eȱȱȱȱȱÆȱȱȱȱAl(l)ȱ
x Liquidȱaluminiumȱ isȱdenserȱ thanȱ theȱ electrolyteȱandȱwillȱbeȱ collectedȱatȱ
theȱbottomȱofȱtheȱcell.ȱ
x Atȱtheȱanode,ȱtheȱoxideȱionsȱareȱdischargedȱtoȱformȱoxygenȱgas.ȱ
2O2Ȭ(l)ȱȱȱÆȱȱO2(g)ȱȱȱ+ȱȱȱȱ4eȱ
55

X TOPIC 2 METALS
16
x Theȱoverallȱchemicalȱreactionȱis:ȱ
2.4
2Al2O3(l)ȱȱȱȱÆȱȱȱ4Al(l)ȱȱȱȱ+ȱȱȱ3O2(g)ȱ
x Theȱoxygenȱliberatedȱatȱtheȱanodeȱwillȱreactȱwithȱtheȱcarbonȱelectrodeȱ
toȱproduceȱcarbonȱdioxideȱgas.ȱ
C(s)ȱȱȱ+ȱȱȱȱO2(g)ȱȱȱÆȱȱȱCO2(g)ȱ
x Consequently,ȱ theȱ anodeȱ isȱ corrodedȱ slowlyȱ andȱ mustȱ beȱ replacedȱ
fromȱtimeȱtoȱtime.ȱ
ȱ
THE USES OF METALS
ȱ
Steel is used more than any other metal. It is important in the building industry. It is
used for girders and for the rods inside reinforced concrete. Steel tubes, called scaffold,
are used when buildings are made or repaired.
Steel is made mainly from iron. It has a small amount of carbon in it. The amount of
carbon affects its properties as can be seen in Table 2.4
Table 2.4: Types of Steel
Type of Steel Amount of Carbon Hardness Uses
Mild steel 0.2% Can be easily shaped Car bodies, wires,
pipe, bicycles
Medium steel 0.3% to 0.6% Hard Girders, springs
High-carbon
steel
0.6% to 1.5 % Very hard Drills, hammers,
other tools
Unfortunately, iron and steel rust. Is there a way to prevent this? You have learned about
alloy. How to make steel alloy?
ȱȱȱȱȱȱȱ
If chromium and nickel are added to steel, you will
get stainless steel, a steel which does not rust!
However,ȱstainlessȱsteelȱisȱexpensive.ȱItȱhasȱmainlyȱbeenȱusedȱforȱmakingȱsmallȱ
items,ȱsuchȱasȱknivesȱandȱspoons.ȱ
ȱȱȱ
ȱ
ACTIVITY 2.3
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱNameȱ20ȱitemsȱthatȱareȱmadeȱofȱstainlessȱsteel.ȱ
56

TOPIC 2 METALS W 17
Another metal that has many useful properties is aluminium. It conducts heat and
electricity well. It has low density for a metal. It does not corrode.
Platinum is used in catalytic converters, fitted to car exhausts. It cuts down the
amount of pollution from cars.
A radioactive isotope of cobalt is used to treat patients with cancer.
Figure 2.14 shows some uses of common metals around the home.
Figure 2.14: Some uses of metals at home
ȱȱȱȱ
ACTIVITY 2.4
Look at the compund of your school. Name the metals and
the uses of metals at your school.
ȱ
ȱȱȱȱȱ
ȱ ȱ
57

X TOPIC 2 METALS
18
ȱ
•ȱ Metalȱ consistsȱ ofȱ atomsȱwhichȱ areȱ arrangedȱ veryȱ closelyȱ packedȱ inȱ anȱ
orderlyȱmanner.ȱ
•ȱ Theȱ atomsȱ inȱmetalȱbondȱwithȱ strongȱ electrostaticȱ forceȱ calledȱmetallicȱ
bond.ȱ
•ȱ Metalsȱ areȱ goodȱ conductorsȱ ofȱ heatȱ andȱ electricity.ȱ Theyȱ areȱ shiny,ȱ
malleableȱ(canȱbeȱhammeredȱintoȱshapes)ȱandȱductileȱ(canȱbeȱdrawnȱoutȱ
intoȱwires).ȱMostȱmetalsȱareȱhard,ȱdenseȱandȱhaveȱhighȱmeltingȱpoints.ȱ
• Theȱpropertiesȱofȱmetalsȱcanȱbeȱimprovedȱwithȱalloying.ȱ
x AlloyȱisȱaȱmixtureȱofȱtwoȱorȱmoreȱmetalsȱorȱaȱmetalȱandȱaȱnonȬmetal.ȱ
x Generally,ȱalloyingȱproducesȱaȱmetallicȱsubstanceȱwhichȱhasȱmoreȱusefulȱ
propertiesȱthanȱtheȱoriginalȱpureȱmetalȱitȱwasȱmadeȱfrom.ȱ
x TheȱReactivityȱSeriesȱlistsȱmetalsȱinȱorderȱofȱreactivity.ȱ
x WeȱcanȱuseȱtheȱReactivityȱSeriesȱtoȱmakeȱpredictionsȱaboutȱreactions.ȱ
x Aȱ moreȱ reactiveȱ metalȱ canȱ displaceȱ aȱ lessȱ reactiveȱ metalȱ fromȱ itsȱ
compound.ȱ
x CarbonȱisȱplacedȱbetweenȱaluminiumȱandȱzincȱinȱtheȱReactivityȱSeries.ȱ
x Extractionȱ ofȱmetalȱ fromȱ itsȱ oreȱ dependsȱ onȱ itsȱ placeȱ inȱ theȱReactivityȱ
Series.ȱTheȱmoreȱreactiveȱaȱmetal,ȱtheȱharderȱitȱisȱtoȱextract.ȱ
x TheȱmetalsȱplacedȱaboveȱcarbonȱinȱtheȱReactivityȱSeriesȱcanȱbeȱextractedȱ
byȱ electrolysisȱ (potassium,ȱ sodium,ȱ lithium,ȱ calcium,ȱ magnesiumȱ andȱ
aluminium).ȱ
x TheȱmetalsȱplacedȱbelowȱcarbonȱinȱtheȱReactivityȱSeriesȱcanȱbeȱextractedȱ
byȱusingȱcarbonȱasȱanȱoxidisingȱagentȱ(zinc,ȱiron,ȱtinȱandȱlead).ȱ
x Metalsȱhaveȱaȱwideȱrangeȱofȱuses.ȱMetalsȱareȱusedȱinȱbuildingȱindustries,ȱ
householdȱproducts,ȱmedicine,ȱagriculture,ȱetc.ȱȱȱ
ȱ
ȱ
ȱ
Blastȱfurnaceȱ
Carbonȱ
Dilutedȱhydrochloricȱacidȱ
Displacementȱreactionȱ
Electrolysisȱ
Heatȱȱ
ȱ
Metalȱ
Metallicȱbondȱ
Reactivityȱseriesȱ
Stainlessȱsteelȱ
Steelȱ
Waterȱ
ȱ
58

TOPIC 2 METALS W 19
ȱ
ȱ
Earl,ȱ B.,ȱ &ȱ Wilford,ȱ D.ȱ (2009).ȱ ȱ IGCSEȱ chemistry.ȱ Unitedȱ Kingdom:ȱ Hodderȱ
Education.ȱȱ
ȱ
Eng,ȱ N.ȱ H.,ȱ &ȱ Lim,ȱ Y.ȱ C.ȱ (2007).ȱ Focusȱ Superȱ Chemistry.ȱ Bangi:ȱ Penerbitanȱ
Pelangi.ȱ
ȱ
Farndon,ȱJ.ȱ(2003).ȱTheȱelements:ȱAluminium.ȱMalaysia:ȱFederalȱPublications.ȱ
ȱ
Ryan,ȱL.ȱ(2001).ȱChemistryȱforȱyou.ȱUnitedȱKingdom:ȱStanleyȱThornes.ȱ
ȱ
Sparrow,ȱG.ȱ(2003).ȱTheȱelements:ȱIron.ȱMalaysia:ȱFederalȱPublications.ȱ
ȱ ȱ
ȱ
59

TOPIC3 : MATERIAL WORLD
TOPIC 4: OXIDATION AND REDUCTION
Readings
Rose Marie Gallgher (1997). Complete Chemistry, Oxford Universiti Press, UK.
Ralph A. Burns (2003). Fundamentals of Chemistry, Prentice Hall, Ney Jersey
Bryan Milner, Jean Martin, John Mills (2002). Core Chemistry, Cambridge Universiti Press
J. G. R. Briggs (2003). Chemistry Insight, Pearson Education Asia Pte. Ltd. Singapore
J.G. R. Briggs (2003). Science in Focus Chemistryfor GCE ‘O’ Level, Pearson Education Asia
Pte.Ltd. Singapore.
Bahagian Pendidikan Guru, KementerianPendidikan Malaysia. (1995) BukuSumber Pengajaran
Pembelajaran Sains Sekolah Rendah, Jilid 3:Strategi Pengajaran dan Pembelajaran Sains.
Projek PIER Bahagian Pendidikan Guru serta dan Bahagian Perancangan dan
Penyelidikan Dasar Pendidikan, Kuala Lumpur.
Whitten, K.W., Davis, R.E.,Peck,M.L and Stanley, GG. (2008). Chemistry (Ninth Edition).2010
Brooks/Cole.
Keywords
- oxidation
- reduction
- oxygen
- ozone
- nonmetal oxides
- metal oxides
Learning Outcomes
At the end of this Topic, the learner will be able to;
1. Define oxidation and reduction.
2. Explain the meaning of redox and giving examples.
63

3. Demonstrate the ability to write balanced formula and the ability to identify oxidizing
agents and reducing from given oxidation-reduction reactions.
4. Ability to differentiate oxygen and ozone.
5. Demonstrate the ability to compare and contrite the properties of oxygen and
hydrogen.
6. Describing with examples the reactions Group 1A and Group 2A with oxygen.
7. Describing what happens to the oxides of Group 1A and Group 2A when it dissolve in
water.
8. Ability to summarize the reactions of O2 with nonmetals ,reactions of nonmetal oxides
with water and the reactions of metal oxides with nonmetal oxides.
Study Questions
Task 1 : Read the definition of oxidation and reduction on Page 225 (highlighted in yellow). In
your own words, describe oxidation and reduction.
Task 2 : It is said that oxidation and reduction occur simultaneously and are referred to as
oxidation-reduction reactions or redox. Read 6-5 Oxidation-Reduction Reactions :
Introduction (pg 225). In your own words explain what redox mean and give examples
in your explanation.
Task 3 : Read Example 6-4 Redox Reactions. After going through and understanding the
section, do the following
(a) write balanced formula unit equations for the following redox reactions:
(i) nitrogen reacts with hydrogen to form ammonia
(ii) aluminum reacts with sulfuric acid to produce aluminum sulfate and hydrogen
(iii) zinc sulfide reacts with oxygen to form zinc oxide and sulfur dioxide
(iv) carbon reacts with nitric acid to produce nitrogen dioxide, carbon dioxide and
water
64

(b) identify the oxidizing agents and reducing agents in the above oxidation-reduction reactions.
Task 4 : Read 5-9 Oxygen and the oxides (pg 198).Can you differentiate between oxygen and
ozone?
Task 5 : Read 5-8 Hydrogen and hydrides (pg 194) and 5-9 Oxygen and oxides (pg 198). In
your own words, compare and contrast the properties of oxygen with those of
hydrogen.
Task 6 : Read Reactions of O2 with metals on page 198-199. Describe in your own words and
with examples, what happens when Group 1A and Group 2A react with oxygen.
Task 7 : Refer to Page 200, Reactions of Metal Oxides with water. Describe what happens to
the oxides of Group 1A and Group 2A when it dissolve in water.
Task 8 : With reference to page 201-203, write a summary of the following reactions:
(v) Reactions of O2 with nonmetals
(vi) Reactions of nonmetal oxides with water
(vii) Reactions of metal oxides with nonmetal oxides.
65

Topiic
3
X Material
LEARNING
1. Explain to students the classes of food and its importance;
2. Conduct a suitable experiment to identify the area of the tongue for different
tastes;
3. Debate about rusty objects; and
4. Conduct suitable experiment to determine the conditions for iron to become
rusty.
X INTRODUCTION
World III
This topic is to teach students about food. As an introduction, you should explain the
importance of food to us. Food is very important to all living beings: humans, animals
and plants. They need food for energy. The energy will be used for growth, development,
repair damaged cells and tissues, reproduction, and maintain general health. In humans
and animals, energy is also used for movement and activity for their everyday life. For
instance, the body cells that are destroyed need to be repaired.
The process of which living organisms obtains food for growing and repairing body cells
is called nutrition. Nutrition is obtained from food. Food provide nutrients. Nutrients
are chemical substances needed in order for us to live and stay healthy. Hence, the energy
is obtained from nutrition in foods utilised to carry out our everyday activities.
66

X TOPIC 3 MATERIAL 34 WORLD III
CHEMICAL PROPERTIES OF MATERIALS
3.1
3.1.1 Classes of Food
To teach the classes of food, you can use the explanation strategy. Firstly, the teacher
should explain the seven classes of food. The basic nutrients we get from foods are
categorised into seven major classes or categories based on their properties. They are:
x Carbohydrates
x Proteins
x Fats
x Vitamins
x Minerals
x Fibres
x Water
Then the teacher can continue the explanation with the functions for every classes of
food. Human and animal bodies need all types of foods to carry out different functions.
The correct proportions of food we consume contain all sources of food. This is called
diet. Diet is the kinds of food we consume and drink regularly.
ACTIVITY 3.1
Testing for the presence of carbohydrate.
The presence of carbohydrate in our food can be tested in the lab. Using tapioca
flour, potato, rice, bread and other samples of food requested by the science
teacher, students may conduct the experiment using iodine solution. Divide your
classroom into several groups for this experiment. Discuss your results.
As mentioned earlier, good diet means we eat food and water at the correct proportions. A
balanced diet should contain about 60% carbohydrates, 20% proteins and 20% fats
coming from food groups. The food will supply nutrients, energy necessary to sustain the
body, for growth and repair and maintain health. The functions of these food are:
(a) Carbohydrates are to supply energy.
(b) Proteins are to provide materials for body growth and repair.
(c) Fats are to supply energy and store excess food.
67

TOPIC 3 MATERIAL WORLD III W 35
(d) Vitamins are to provide maintenance and healthy body.
(e) Mineral salts are for healthy teeth, bones, muscles and other parts of the body.
(f) Fibres are to help intestines to function properly.
(g) Water is to process all chemicals in the body and transport substances in the blood.
Lastly, you should explain the importance of the right proportion of the food consumed
everyday. We should eat the right types and amount of food daily to get all the energy
needed. This is called a balanced diet. In order to do this, the relative amounts of different
kinds of food eaten by a person has to be considered. The type of foods consumed can be
illustrated in the form of a Food Pyramid as shown in Figure 3.1.
Figure 3.1: Food Pyramid
Source: www.lifeclinic.com/foods/nutrition/foodpyramid.asp
68

ACTIVITY 3.2
Balanced diet
Balanced diets provide all essential nutrients in the correct amount and
proportion of food. It should contain all the seven classes of food. Adults,
adolescents and children need diet with different proportion. Divide your
classroom into seven groups to represent each class of food. In your assigned
group, discuss the factors that determine a person’s balanced diet. List all
factors and present the findings to the class.
3.1.2 Taste of Foods
To teach this lesson, you can use the experiment strategy. Before we do the experiment,
the teacher should explain about the taste of foods. We eat all kinds of food. Food have
different tastes. Food can be categorised into different tastes: sweet, sour, bitter and salty.
Other kinds of tastes are the combinations of these four major tastes. The taste of food
can be detected only by a sensory organ in our mouth called the tongue. The tongue is the
sensory organ that has sensitive cells on the surface. These cells are called taste buds
which contain many taste receptors. These receptors detect the different type of tastes of
our foods. However, the taste of foods can only be detected at different areas on the
tongue (Figure 3.2)
Figure 3.2: Area of the tongue responding to different tastes
Source: http://library.thinkquest.org/3750/taste/taste.html
After explaining the different areas on the tongue that can detect different tastes, you can
use the following experiment to give your students the experience of different types of
taste.
69

3.1.3 Acids and Alkalis
Food are grouped based on their tastes. They are sweet, sour, bitter and salty. Foods that
are sour belong to the acid group. The word “acid” is from the Latin word “acidus” which
means sour. Many sour fruits, especially those which are not ripe, contain acid. All acids
are not of the same strength; some are strong and some are weak. Other food or fruits that
are bitter fall in the alkali group. There are also strong and weak alkalis (see Figure 3.3).
ȱ
ACTIVITY 3.3
Taste areas of the tongue
This is a lab activity. Work in pairs of two. Blindfold your partner. Pour little
amount of solutions of different tastes: salty (salt solution); sweet (sugar
solution); sour (lime juice); and bitter (coffee). Ask your partner to rinse his
tongue with distilled water. Using a straw, place a drop of salt solution onto the
tip of his tongue. Ask him to identify the taste without pulling his/her tongue.
Record your results using a table whether your partner is right (/) or wrong (x).
Repeat the steps on four other areas (tastes) of his tongue but make sure that he
rinses the tongue using the distilled water before each solution is repeated.
70

ȱ
Figure 3.3: Acidic and alkaline foods and fruits
Source: http://buywaterfilter.my
Using a specific procedure in the lab, you can use a litmus or pH paper to test the
presence of acid or alkali in the substances you select. Most of the time, materials
containing acid will turn the blue litmus or pH paper to red colour. On the other hand,
alkali will turn the red litmus or pH paper to blue. (Figure 3.4). Can you list at least two
substances in your everyday life in both groups of acid and alkali?
Figure 3.4: pH scale ranges from 1 to 14 to indicate the strength of an acid or alkali
Source: dtc.prima.edu/~biology/.../lesson2d.htm
71

ACTIVITY 3.4
Identification of substances: acidic or alkaline
You can ask your students to bring anything from home like fruit (lemon, lime,
mango, guava, papaya, banana, etc.) carbonated drink, toothpaste, detergent,
soap, shampoo, hair conditioner, milk, vinegar, distilled water or others by your
science teacher. In the laboratory, you will be conducting an experiment to
identify those substances whether they are acid or alkali. Use the litmus or pH
paper to indicate the presence of acid and alkali.
Source: dtc.prima.edu/~biology/.../lesson2d.htm
3.1.4 Household Products
You can also explain further the use of acid and alkali for cleaning purposes. Different
objects in the house will require different types of cleaning products; hence, we need to
use the products that have specific functions. The household products can be categorised
into two groups: acidic or alkaline. Most of the household products like alkaline are
sodium hydroxide (for making soap and detergent); ammonia (household cleaner,
drainage opener, sink opener), lime (to raise the pH value of acidic soil for healthy
growth of plants); magnesium hydroxide (used in antacid to ease stomachache due to
excessive acid); toothpaste; baking soda solution; bleach; and many more.
The other group of household products like nitric acid (to make fertiliser and dye); citric
acid and tartaric acid (to make fruit salt); acetic acid (to make synthetic fibre); boric acid
(an eyewash); benzoic acid (to preserve food); carbonic acid (in carbonated drinks);
lemon juice (for drinks); vinegar; and sulfuric acid (liquid from car battery); are some
example of uses of acids. I believe, you can find and name more of the household
products surrounding you from the departmental store during your shopping, as compared
to browsing through the Internet! Then you can use this example to explain or discuss
with your students.
72

ACTIVITY 3.5
Browse through the Internet. Find out on how to make:
1. Soap (using alkali)
2. Salt (using alkali and acid)
Write your report and present them to the class according to groups.
RUSTING
3.2
3.2.1 Investigate Material that can Rust Up
Start this lesson by asking student these questions; when you walk at the children
playground, can you trace which objects can become rusty and which ones cannot? Can
you differentiate the properties of the objects that can rust and which one cannot? (Figure
3.5)
Figure 3.5: Playground
Source: http://boston.about.com/od/walkingtours/ss/bcWalkingTour_6.htm
Objects that are made from iron and steel can become rusty. These objects have a
reddish-brown stuff formed on their surface when rusty. The mass of the objects will
increase when the rust formed on the surface. This process of rust formation is known as
rusting. However, not all objects can become rusty. Objects made from clay, wood, fibre,
73

plastic and glass are the few examples of non-rusty objects. Find and list more examples
about rusty and non-rusty objects. To make the teaching process more interesting, you
can ask students to do the activity below:
ACTIVITY 3.6
Should we replace all rusty objects with non-rusty objects? Form your own
group and make your stand whether you are for or against this motion.
3.2.2 Why do Objects Rust?
Before this, we have learned that objects made of iron and steel can become rusty. For
example, a nail, can become rusty. When you compare a nail in your house and the nail
outside the house, why is the nail outside the house often rusty? Can you explain this
phenomenon? Is it possible for us to infer why that one nail has become rusty, but others
still look gray and shiny? Why do objects like nails rust? To understand this behaviour,
we need to learn some chemical reactions which underlies the process of rusting. Perhaps
you have never heard of oxidation reactions. Yet, this type of reaction has many
important applications in our everyday life. When you see a rusty nail, you are actually
observing a process of oxidation.
Historically, the term oxidation was used for reactions of the elements with oxygen to
form oxides. All metals exhibit a tendency to be oxidised, some more easily than others.
Metals used in building materials, such as iron, eventually oxidise, which causes
deterioration of the metal. Known as corrosion, this process results in rust and other
corrosion on cars, bridges, ships and underground pipes.
74

Figure 3.6: An abandoned rusty car
Source: http://www.nsls.bnl.gov/about/everyday/corrosion.html
3.2.3 Factors Needed for Iron to Rust
Now we know that iron can become rusty through the process of oxidation. What is the
meaning of oxidation? To understand this, we should identify the determining factors
needed for iron to rust. Then ask your students to do the experiment below:
75

ACTIVITY 3.7
Experiment 1: Rusting
Students will conduct experiment to determine what conditions are necessary
for iron to change into the iron oxide compound.
Materials:
x Test tubes (4)
x Stopper
x Test tube rack
x 100ml graduated cylinder
x 250ml cylinder
x Few pieces of nails
x Salt
x Pencil
Procedure:
1. Students work in groups of four.
2. Students hypothesise which nail will rust.
3. Students will be given data table.
4. Label the test tubes W, X, Y, and Z.
5. Measure 50ml of vegetable oil and pour into a 100ml beaker.
6. Measure 50ml of water and pour into a second 100ml beaker.
7. Measure 50ml of water and pour into third 100ml beaker. Add salt until
no more salt will dissolve.
8. Place one piece of nail into each of the three 100ml beakers. Drop the
fourth nail into the test tube W. Put a stopper on the test tube and place
in the test tube rack.
9. Use forceps to remove the nail from the oil and place into the bottom of
test tube X. Place in the rack.
10. Repeat the process for the nail from both water and salt solutions and
place into test tubes Y and Z.
11. Students work in groups of four.
76

12. Students hypothesise which nail will rust.
13. Students will be given data table.
14. Label the test tubes W, X, Y, and Z.
15. Measure 50ml of vegetable oil and pour into a 100ml beaker.
16. Measure 50ml of water and pour into a second 100 ml beaker.
17. Measure 50ml of water and pour into third 100ml beaker. Add salt until
no more salt will dissolve.
18. Place one piece of nail into each of the three 100ml beakers. Drop the
fourth nail into the test tube W. Put a stopper on the test tube and place
in the test tube rack.
19. Use forceps to remove the nail from the oil and place into the bottom
of test tube X. Place in the rack.
20. Repeat the process for the nail from both water and salt solutions and
place into test tubes Y and Z.
21. Measure 100ml of water into the 250ml beaker. Tape the four test tubes
together and invert them into the beaker and support them.
22. Record your observations in the data table everyday for three days.
Data and observation
Test tube Day one Day two Day three
W The nail still looks
gray and shiny
The nail still looks
gray and shiny
gray and shiny
X The nail still looks
gray and shiny
gray and shiny
gray and shiny
Y A reddish-brown stuff
appears on the surface
of the nail
A reddish-brown
stuff appears on the
surface of the nail
A reddish-brown
surface of the nail
Z More reddish-brown
surface of the nail
compared to Y
More reddish-brown
surface of the nail
compared to Y
More reddish-brown
surface of the nail
compared to Y
77

Questions:
1. In which test tubes did the nail change into the compound iron oxide?
2. Why didn't the nails rust in the other test tubes?
3. What factor increased the rate of the reaction? Why?
4. What was the purpose of test tube W?
5. What is necessary for the formation of the compound iron oxide?
Answers:
1. In test tubes Y and Z
2. Either oxygen or water was not in contact with the nail. In test tube W,
the lack of water prevented the iron from oxidising. In test tube X, the
vegetable oil protected the nail from rusting
3. Salt increased the rate of chemical change. The salt solution cleaned the
surface of the nail
4. Control
5. Iron, oxygen and water
Here are some tips that you can give to your students when they are doing a science
project or experiment.
Tips
To do science project systematically, you may follow the following steps. First, you
must realise the purpose of doing this science project (Are you testing different
substance that are able to prevent rust from forming? Or, to determine which rust
remover was more efficient in removing rust from iron?).
Secondly, you should determine the hypothesis of this experiment. You can create your
hypothesis creatively, but I suggest you to consider substance that you believe to be the
most effective in preventing the act of rust.
78

Thirdly, you should design your experiment in order to test your hypothesis. You
should recognise which variable is constant, how you can manipulate certain variable
and observe or measure the effect of this manipulated variable on certain independent
variable. You may discuss with your friends about the variable which is to be held
constant for this experiment However, it is suggested that different kind of rust
inhibitor as the manipulated variable. Rust inhibitor is defined as a substance to prevent
the act of rust from occurring. Paints are used on cars, bridges and many other items
that are usually exposed to damp air. In car radiators, anti-freeze is used since is has a
high boiling point, allowing the car to run at a high temperature without boiling away
the coolant and contains chemicals that can inhibit water’s tendency to rust. Tinplate is
used for manufacturing cans and protects the steel from rusting and corrosion. Waxes
are used in manufacturing as rust preventatives. Well, now we have already determined
which element act as manipulated variable. How about the dependent or responding
variable? Can you find any material around your house to be used as the responding
variable? Maybe you can use a nail, since it is cheap and easy to obtain.
After you have collected all the relevant materials, the fourth step you should do is to
conduct the experiment. The rust inhibitors which act as manipulated variable in this
experiment are the paint, the paraffin wax and the car polish. Therefore, we can decide
that there are three experimental groups in this study and one control group. Following
are the detail of each group.
Group Characteristic
Experiment 1 A nail coated with paraffin wax
Experiment 2 A nail coated with paint
Experiment 3 A nail coated with car polish
Control Does not have any rust inhibitor applied on it
Let all the nails dry overnight. After you have let the nails dry, sprinkle them with tap
water on the morning, afternoon and evening. Do this for a week. After a week, can
you discover which nail has a lot of rust and which nail doesn’t? After you have the
result, what can you conclude?
At the end of this lesson, you can ask students to make conclusion. What can they
conclude from this experiment? Let us read more to relate with the findings. Three things
are required for iron to turn into iron oxide. These things are water, oxygen and iron
itself. When a drop of water strikes an iron object, two things begin to occur almost
instantaneously. First, the water, a good electrolyte, combines with carbon dioxide in the
air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the
iron dissolved, some of the water will begin to break down into its component, that is
hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the
79

process of freeing the electrons. The electrons liberated from the anode portion of the iron
flow to the cathode, which may be a piece of a metal less electrically reactive than iron,
or another point on the piece of iron itself.
The chemical compounds found in liquids like acid rain and seawater, make them better
electrolytes than pure water. This allows their presence to speed up the process of rusting
on iron and other forms of corrosion on other metals. The type of metal also plays a big
role in the rate at which corrosion occurs. For example, chromium corrodes much slower
than iron. Other valuable metals like sterling silver, platinum and gold are hardly
corroded at all. The environment also plays a role in corrosion. Metals corrode faster in
hot humid climates and slower in cold dry ones.
Another way to understand how the process of rusting happens is through several
chemical equations. The process of rusting requires an anode and cathode in different
places on the surface of a piece of iron. In one area of the iron (Fe) surface, called the
anode region, the oxidation half reaction takes places.
Anode (oxidation): Fe(s) Æ Fe2+(aq) + 2e-
or 2Fe(s) Æ 2Fe2+(aq) + 4e-
The electrons move through the iron metal from anode to an area called the cathode
region where oxygen (O2) dissolved in water is reduced to water (H2O).
Cathode (reduction): O2(g) + 4H+(aq) + 4e- Æ 2H2O(l)
By combining the half reactions that occur in the anode and cathode regions, we can write
the overall oxidation-reduction process.
2Fe(s) + O2(g) + 4H+(aq) Æ 2Fe2+(aq) + 2H2O(l)
The formation of rust occurs as Fe2+ ions move out of the anode region and come in
contract with dissolved oxygen (O2). The Fe2+ oxidises to give Fe3+, which reacts with
oxygen to form of rust.
4Fe2+(aq) + O2(g) + 4H2O(l) Æ 2Fe2O3 + 8H+(aq)
We can write the formation of rust starting with solid Fe reacting with O2 as follows.
There is no H+ in the overall equation because H+ is produced in equal quantities.
Corrosion of iron
4Fe(s) + 3O2(g) Æ 2Fe2O3
Rust
80

3.2.4 Protection Against Rust
Rusty objects look unattractive and old. They become brittle and corrode slowly.
Basically, we can prevent rusting by preventing the iron objects from coming into contact
with air and water. This can be done by coating the objects with non-rusting material like
paint, oil, grease or any non-rusting materials. Iron objects also can be galvanised to
prevent the iron from rusting.
Other than that, we can also remove rust by using electrolysis (see Figure 3.7). In doing
this, you need a plastic bucket, battery charger, baking soda and electrode. It can be done
by providing a flow of electrical current and the rust will move with the electrical current.
To get the current flow, fill your plastic bucket with water. Add about a tablespoon of
baking soda per gallon to the water. Once the current is started, adding more soda will not
make the process go faster. Put the object into the water with the NEGATIVE lead on it.
Now, put in your electrode which could be a nail, screw, or any piece of metal. Stainless
steel works the best. Then, attach the POSITIVE lead to the “electrode”. Now switch
ON the battery charger and observe the rust going away.
Figure 3.7: The process of electrolysis
Source: http://www.thepontiactransampage.com/rust.html
3.2.5 The Benefits of Protection against Rust
The problem associated with rusting can be associated with utilities, transportation and
infrastructure. Therefore, it is important to prevent metals around us, especially iron, from
rusting. An old iron object need not be replaced if we can prevent it from rusting.
Therefore, it will save cost. Iron objects which are not rusty look shiny and new
compared to iron objects which have become rusty. Look at Figure 3.8. It shows a
photograph of a badly corroded truck after many years of marine atmospheric exposure.
81

Figure 3.8: A badly corroded truck after many years of marine atmospheric exposure
Source: http://www.electrochem.org/dl/interface/spr/spr06/spr06_p24-26.pdf
The teacher also can give students a group work assignment and science project as
activity below so that they can understand better.
ACTIVITY 3.8
There are so many mega structures in Malaysia. Yet, our country has a climate
that is humid and hot. Based on this circumstance, it is possible that rusting is
one of the problems which are faced by us in Malaysia when maintaining those
mega structures. Can you find information to show an example about how to
maintain one of the mega structures in Malaysia which is associated with
rusting? Do some presentation in front of the class to report about your work.
ACTIVITY 3.9
Conduct a science project to investigate the most effective way to protect iron
object against rust. Do some demonstrations to compare several methods which
are used to prevent materials from rusting.
82

x Food can be categorised into seven classes: carbohydrates, proteins, vitamins, fats,
minerals, fibres and water.
x Food have different tastes. They are sour, sweet, bitter and salty.
x Food are also classified into two groups. They are acid and alkali.
x Acid changes the blue litmus paper to red. While, alkali turns the red litmus paper to
blue.
x Household products are also divided by the characteristics of being acidic and
alkaline.
x Materials can be divided into rusty and non-rusty objects.
x Rusting process is due to the presence of water, oxygen and iron. This process is
called oxidation.
x Rust can be prevented by certain methods like painting, galvanising and electrolysis
of the metals.
x There are benefits through the prevention against rust. Some metals can stay longer
and have a good looking appearence because of the prevention from rusting.
Acid
Alkali
Bitter
Corrosion
Iron
Oxidation
Oxygen
Rust
Salty
Sour
Sweet
Water
83

Burns, R. A. (1992). Fundamentals of chemistry (2nd ed.). Englewood Cliffs, NJ:
Prentice Hall.
Hazen, R. M. , & Trefil, J. (1997). The physical sciences: an integrated approach. New
York, NY: John Wiley & Son, Inc.
Kotz, J. C., Treichel, P. M. & Weaver, G.C. (2006) Chemistry and chemical reactivity
(6th ed.). Belmont, CA: Thomson Brooks/Cole.
Milner, B., Martin, J., & Mills, J. (2002). Core chemistry. Cambridge: Cambridge
University Press.
Timberlake, K. C. (2005). Basic chemistry. San Francisco, CA: Pearson
Education Co.
Abandoned rusty car (n.d). http://www.nsls.bnl.gov/about/everyday/ corrosion.html
Retrieved July 6, 2007.
Area of tongue (n.d). http://greenfield.fortunecity.com/rattler/46/upali2.htm Retrieved
July 7, 2007.
Badly corroded truck. (n.d). http://www.electrochem.org/dl/interface/spr/
spr06/spr06_p24-26.pdf Retrieved July 6, 2007.
Food Pyramid. (n.d). www.lifeclinic.com/foods/nutrition/foodpyramid.asp Retrieved July
7, 2007.
Household products. (n.d). http://images.search.yahoo.com/search/images/
householdproducts Retrieved July 7, 2007.
pH scale. (n.d). dtc.prima.edu/~biology/.../lesson2d.htm Retrieved July 7, 2007
The process of electrolysis (n.d). http://www.thepontiactransampage. com/rust.html
Retrieved July 6, 2007.
84

Rao, C. N. R.. Understanding Chemistry.
: World Scientific Publishing Co., . p 238
http://site.ebrary.com/id/10422534?ppg=238
Copyright © World Scientific Publishing Co.. . All rights reserved.
May not be reproduced in any form without permission from the publisher,
except fair uses permitted under U.S. or applicable copyright law.
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134

Topiic 5 X SpeedȱOfȱ
ȱ ȱ ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
X INTRODUCTIONȱ
Chemicalȱ
Reactionsȱ
LEARNING OUTCOMES
1. Define the speed of chemical reaction;
2. Calculate the speed of a chemical reaction;
3. Distinguish the effects of particle size, concentration, pressure,
temperature and catalysts on the speed of chemical reaction; and
4. Evaluate the effect of activation energy on the speed of a reaction.ȱ
Ifȱ thereȱ isȱ aȱ runningȱ competitionȱ betweenȱ aȱ rabbitȱ andȱ aȱ tortoise,ȱ whichȱ
animalȱwillȱwin?ȱSurelyȱtheȱanswerȱwillȱbeȱtheȱrabbitȱ(ifȱtheȱrabbitȱdoesȱnotȱ
fallȱasleepȱduringȱtheȱcompetition,ȱthatȱis).ȱRabbitsȱrunȱfasterȱthanȱtortoises.ȱ
Theȱ tortoiseȱ willȱ getȱ toȱ thefinishȱ lineȱ eventually,ȱ butȱ willȱ probablyȱ reachȱ
thereȱmuchlater.Thisȱmeansȱ thatȱ theȱ rabbitȱ runsȱataȱgreaterȱ speedȱ thanȱ theȱ
tortoise.ȱ
ȱ
Inȱ everydayȱ life,ȱ ifȱ youȱ putȱ granulatedȱ sugarȱ andȱ fineȱ sugarȱ inȱ differentȱ
glassesȱofȱwaterȱwithȱ theȱ sameȱvolumeȱandȱ temperature,ȱwhichȱ sugarȱwillȱ
dissolveȱfirst?ȱ
ȱ
ȱ
Yes! fine sugar will dissolvefirst. It is because fine sugar
ȱ
has a larger surface area that comes in contact with water.
ȱ
ȱ
ȱ
137

X T
2
TOPIC5 SPEE
Whenȱcoo
ordinaryȱ
refrigerato
everydayȱ
ȱȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ED OF CHEMIC
okingȱmeat,ȱit
pot.ȱEverȱwo
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occurrencesȱ
A
CAL REACTIO
tȱisȱbetterȱtoȱu
onderedȱwhy?
erȱ toȱ goȱ rott
areȱactuallyȱth
ACTIVITY 5.1
Wh
Put
exp
An
x
x
x
1
hich metal disso
t magnesium p
periment by repl
nswer the follow
ȱ ȱȱȱ
5.1
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useȱaȱpressure
?ȱWhyȱdoȱve
ten?ȱ Doȱ youȱ
heȱresultȱofȱch
olves faster in an
powder in a te
lacing the magn
wing questions:
of magnesium (t
any bubble relea
e what type of g
Which form o
Did you see a
Can you state
eȱcookerȱrathe
getablesȱthatȱ
realiseȱ thatȱ
hemicalȱreact
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st tube contain
esium powder w
erȱthanȱusingȱ
areȱkeptȱinȱt
theseȱ commo
tions?ȱȱ
through this acti
ning hydrochlor
with a magnesium
the powder or th
ased?
as was released?
ITIONȱO
DEFINI
Theȱ speed
changeȱin
productsȱ
rateȱatȱwh
dȱ ofȱ reaction
nȱconcentratio
perȱunitȱ time
hichȱtheȱreacta
5.1.1ȱC
anȱ
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ric acid. Repea
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micalȱreaction
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changes.ȱPhy
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mesȱ gassesȱ if
eȱ isȱ formed.ȱ
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eactions?ȱ Inȱ
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However,ȱ in
ppensȱ whenȱ
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lphurȱ andȱ ir
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138

[Source
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powderȱ
youȱheat
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ACTIVITY 5
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mixture. Put th
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micalȱequation
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139

X TOPIC5 SPEED OF CHEMICAL REACTIONS
4
5.1.2ȱ NatureȱofȱChemicalȱReactantsȱ
Inȱ orderȱ forȱ aȱ reactionȱ toȱ occur,ȱ thereȱ mustȱ beȱ aȱ collisionȱ betweenȱ theȱ
reactantsȱatȱtheȱreactiveȱsiteȱofȱtheȱmoleculeȱwithȱcorrectȱorientationȱandȱitȱ
hasȱ toȱ achieveȱ activationȱ energy.ȱ Thisȱ willȱ leadȱ toȱ effectiveȱ collisionȱ andȱ
chemicalȱreactionȱwillȱoccur.ȱ
ȱ
Figureȱ5.3:ȱParticlesȱshowingȱtheȱeffectiveȱandȱineffectiveȱcollisionȱ
[Source:ȱhttp://2012books.lardbucket.org/books/principlesȬofȬgeneralȬ
chemistryȬv1.0m/s18Ȭ07ȬtheȬcollisionȬmodelȬofȬchemica.html]ȱ
ȱ
Particlesȱmightȱ beȱ atoms,ȱmoleculesȱ orȱ ions.ȱBeforeȱweȱ canȱ getȱ aȱ chemicalȱ
reaction,ȱparticlesȱmustȱcrashȱtogether.ȱTheyȱmustȱcollide.ȱThisȱisȱcalledȱtheȱ
collisionȱtheory.ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱ
Figureȱ5.4:Collisionbetweenȱparticlesȱ
[Source:ȱhttp://minhaji.net/classes/ȱ3107]ȱ
ȱ
140

TOPIC 5 SPEED OF CHEMICAL REACTIONS W 5
5.1.3ȱ SpeedȱofȱChemicalȱReactionȱ
Theȱareaȱofȱchemistryȱconcernedȱwithȱtheȱspeedȱorȱratesȱatȱwhichȱaȱchemicalȱ
reactionȱ occursȱ isȱ calledȱ chemicalȱ kinetics.ȱ Theȱ wordȱ “kinetic”ȱ suggestsȱ
motion.ȱHere,ȱkineticsȱrefersȱtoȱtheȱspeedȱofȱaȱreaction,ȱorȱtheȱreactionȱspeed,ȱ
whichȱisȱtheȱchangeȱofȱtheȱconcentrationȱofȱreactantȱorȱproductȱwithȱtime.ȱȱ
ȱ
ȱ
Speed of chemical reaction is the speed at which reactants
ȱ
are converted into the products in a chemical reaction.
ȱ
ȱ
ȱ
Letȱusȱlookȱatȱtheȱgeneralȱequation:ȱ
ȱ
ReactantsȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱProductsȱ
ȱ
Thisȱ equationȱ tellsȱ usȱ that,ȱ duringȱ theȱ courseȱ ofȱ aȱ reaction,ȱ reactantȱ
moleculesȱareȱconsumedȱwhileȱproductȱmoleculesȱareȱformed.ȱTwoȱobviousȱ
changesȱwillȱoccur,ȱnamely:ȱ
i. Theȱdecreaseȱinȱtheȱquantityȱofȱaȱreactantȱwithȱtime;ȱandȱȱ
ii. Theȱincreaseȱinȱtheȱquantityȱofȱaȱproductȱwithȱtime.ȱȱȱ
Asȱaȱresult,ȱweȱcanȱfollowȱtheȱprogressȱofȱaȱreactionȱbyȱmonitoring:ȱ
i. Eitherȱ theȱ decreaseȱ inȱ concentrationȱ ofȱ theȱ reactantsȱ orȱ theȱ
increaseȱinȱconcentrationȱofȱtheȱproducts;ȱ
ii. Decreaseȱ inȱ theȱ massȱ ofȱ reactantȱ orȱ increaseȱ inȱ theȱ massȱ ofȱ
product;ȱ
iii. Increaseȱinȱtheȱvolumeȱofȱgasȱreleased;ȱ
iv. Formationȱofȱprecipitateȱasȱaȱproduct;ȱorȱ
v. ChangeȱinȱpH,ȱtemperatureȱorȱelectricalȱconductivity.ȱȱ
Forȱreactionsȱthatȱoccurȱrapidly,ȱtheȱspeedȱofȱreactionȱisȱhigh.ȱConversely,forȱ
aȱreactionȱthatȱoccursȱslowly,theȱspeedȱofȱreactionȱisȱlow.ȱTheȱtimeȱtakenȱforȱ
aȱfastȱreactionȱisȱshort,ȱwhereasȱtheȱtimeȱtakenȱforȱaȱslowȱreactionȱisȱlong.ȱ
ȱ
Howȱdoȱwemeasureȱtheȱspeedȱofȱchemicalȱreaction?ȱ
141

X T
6
ȱ
5.2
TOPIC5 SPEE
Toȱseeȱho
aȱlookȱatȱt
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ED OF CHEMIC
CAL REACTIO
GȱTHEȱSP
REACTIO
SURING
MICALȱR
ofȱaȱchemical
ȱexample:ȱȱ
entȱ5.1ȱ(TheȱRe
Experime
ȱ
1. Fillȱthe
lȱreactionȱisȱac
eactionȱbetwee
eȱbasinȱandȱbu
eniscusȱatȱ50cm
htȱ6gȱofȱmedium
theȱme
2. Weigh
flask.ȱ
enȱMarbleȱChip
retteȱwithȱwat
m³ȱ(Figureȱ5.4).
mȱmarbleȱchips
ureȱ50cm³ȱofȱ0.1
ourȱitȱintoȱtheȱc
diately,ȱcoverȱt
heȱstopwatchȱa
dȱ theȱ volumeȱ
ds.ȱ
heȱ graphȱ ofȱ th
axisȱasȱinȱExper
lateȱtheȱaverag
teȱofȱreactionȱin
3. Measu
andȱpo
4. Immed
Startȱth
5. Record
second
6. Plotȱ th
sameȱa
7. Calcul
theȱrat
S
Des
liber
MEAS
CHEM
wȱtheȱspeedȱo
theȱfollowing
Fȱ
ured,ȱletȱusȱta
psȱandȱHydroc
er.ȱInvertȱtheȱb
chloricȱAcid)ȱ
buretteȱintoȱthe
sȱ(inȱexcess)ȱan
1ȱmolȱdmƉ³ȱhy
conicalȱflask.ȱ
theȱconicalȱflas
atȱtheȱsameȱtim
ofȱ gasȱ collect
eȱbasinȱandȱma
ndȱputȱtheȱchip
drochloricȱacid
psȱintoȱtheȱconic
dȱusingȱtheȱme
skȱwithȱaȱrubb
me.ȱ
tedȱ inȱ theȱ bur
heȱ volumeȱ ofȱ c
rimentȱ5.1ȱ
geȱrateȱofȱreact
nȱtheȱsecondȱm
Figure 5.5: W
easuringȱcylind
erȱstopperȱand
dȱshakeȱtheȱflas
retteȱ everyȱ 30ȱ
carbonȱ dioxide
eȱ releasedȱ aga
tion,ȱtheȱrateȱo
minutesȱforȱthisȱ
Water displaceme
SELF-CHECK
cribeȱ oneȱ oth
ratedȱfromȱEx
ainstȱ timeȱ onȱ t
ofȱreactionȱatȱ5
experiment.ȱ
ent method to co
IVITY5.3ȱ
CTI
K 5.1
herȱ methodȱ
xperimentȱ5.1
50ȱsecondsandȱ
oxide gasȱ
ollect carbon dio
thatȱ canȱ beȱ
1
NS
PEEDȱOF
ONȱ
ctuallyȱmeasu
secondsȱ forȱ 3
usedȱ toȱ colle
ectȱ theȱ gasȱ
akeȱ
arkȱ
calȱ
derȱ
sk.ȱ
360ȱ
theȱ
inȱ
142

Theȱ chemicalȱ equationȱ forȱ theȱ reactionȱ betweenȱ marbleȱ chipȱ (calciumȱ
carbonate,ȱCaCO3)ȱandȱhydrochloricȱacidȱis:ȱ
CaCO3(s)ȱ+ȱHCl(aq)ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱCaCl2(aq)ȱ+ȱCO2(g)ȱȱ+ȱH2O(l)ȱ
ȱ
Figureȱ 5.6ȱ showsȱ theȱ volumeȱ ofȱ carbonȱ dioxideȱ gasȱ releasedȱmeasuredȱ atȱ
certainȱintervalsȱplottedȱagainstȱtime.ȱ
ȱ
ȱ
ȱ
VolumeȱofȱCO2ȱgas/ȱcm3ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Time/minȱ
ȱ
Figureȱ5.6:Theȱvolumeȱofȱcarbonȱdioxideȱgasȱliberatedȱagainstȱtimeȱȱ
ȱ
Howȱfastȱareactionȱprogressesȱoverȱanȱintervalȱofȱtimeȱisȱtheȱaverageȱspeedȱ
ofȱreaction.ȱItȱisȱcalculatedȱasȱfollows:ȱ
ȱ
Averageȱspeed=ȱTheȱchangeȱinȱtheȱamountȱofȱreactantȱorȱproductȱ
ȱ ȱ Theȱtimeȱtakenȱforȱtheȱchangeȱtoȱhappenȱ
ȱ
FromȱtheȱgraphȱinȱFigureȱ5.6,ȱweȱcanȱcalculateȱtheȱaverageȱspeedȱofȱchemicalȱ
reactionȱbetweenȱmarbleȱchipȱandȱhydrochloricȱacid.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
143

8
Averageȱspeedȱofȱreactionȱ=ȱTheȱtotalȱvolumeȱofȱcarbonȱdioxideȱgasȱreleasedȱ
ȱ ȱȱȱTimeȱtakenȱforȱtheȱtotalȱcarbonȱdioxideȱgasȱreleaseȱ
ȱ
ȱ =ȱȱ94.00cm3ȱ
ȱ ȱȱȱȱȱ4.5ȱminȱ
ȱ =ȱ20.90cm3minȬ1ȱ
ȱ
Canȱyouȱcalculateȱtheȱspeedȱofȱreactionȱatȱanyȱgivenȱtime?ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Letȱusȱtakeȱaȱlookȱatȱtheȱnextȱexample:ȱ
ȱ
Basedȱonȱtheȱgraphȱofȱvolumeȱofȱcarbonȱdioxideȱgasȱliberatedȱagainstȱtimeȱ
(Figureȱ5.6),ȱyouȱcanȱalso:ȱ
ȱ
a. Calculateȱtheȱaverageȱrateȱofȱreactionȱinȱtheȱfirstȱoneȱminute;ȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ ȱ
Figureȱ5.7:ȱTheȱaverageȱrateȱofȱreactionȱinȱtheȱfirstȱoneȱminuteȱȱ
ȱ
ȱ
Theȱexactȱspeedȱofȱreactionȱatȱanyȱgivenȱtimeȱisȱȱ
calledȱtheȱinstantaneousȱspeedȱofȱreaction.ȱ
Volume of CO2 gas/ cm3
Time/min
144

Theȱaverageȱrateȱofȱreactionȱinȱtheȱfirstȱoneȱminuteȱ
ȱ =ȱTotalȱvolumeȱofȱCO2ȱcollectedȱinȱtheȱfirstȱ1ȱminuteȱ
ȱ ȱ ȱ Timeȱtakenȱ
ȱ =ȱ54.00cm3ȱ
ȱ ȱȱȱȱ1ȱminȱ
ȱ =ȱ54.00cm3minȬ1ȱ
ȱ
b. Calculateȱtheȱaverageȱrateȱofȱreactionȱfromȱ1ȱminuteȱtoȱ2ȱminutes;ȱandȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ5.8:Theȱaverageȱrateȱofȱreactionȱfromȱ1ȱminuteȱtoȱ2ȱminuteȱ
ȱ
ȱ
Theȱaverageȱrateȱofȱreactionȱfromȱ1ȱminuteȱtoȱ2ȱminutesȱ
ȱȱȱȱȱȱȱȱȱȱ=ȱTotalȱvolumeȱofȱCO2ȱcollectedȱfromȱ1ȱminuteȱtoȱ2ȱminutesȱ
ȱ ȱȱȱȱȱȱȱȱȱTimeȱtakenȱ
ȱȱȱȱȱȱȱȱȱȱ=ȱ(77.00–ȱ54.00)cm3ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱ(2Ȭȱ1)ȱminȱ
ȱȱȱȱȱȱȱȱȱȱ=ȱȱ23.00cm3ȱ ȱ
ȱ ȱȱȱ1ȱminȱ
ȱȱȱȱȱȱȱȱȱȱȱ=ȱ23.00cm3minȬ1ȱ
ȱ
ȱ
ȱ
ȱ
Time/min
145

10
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
c. Calculateȱ theȱ averageȱ speedȱ ofȱ reactionȱ attheȱ 2ȱ minutespointȱ byȱ
drawingaȱtangentȱatȱtheȱcurveȱpoint.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ5.9:Theȱaverageȱspeedȱofȱreactionȱcalculatedbyȱdrawingȱaȱtangentȱlineȱ
atȱtheȱcurveȱpointȱ
ȱ
Theȱspeedȱofȱreactionȱatȱtheȱ2ndȱminuteȱ=ȱTheȱgradientȱofȱtheȱtangentȱofȱtheȱ
ȱ ȱ ȱ ȱ ȱ graphȱatȱtheȱsecondȱminuteȱ
ȱ
Theȱspeedȱofȱreactionȱatȱtheȱ2ndȱminuteȱ =ȱ100.00ȱ–ȱ50.00cm3ȱ
ȱ ȱ 3.3ȱ–ȱ0.4ȱminȱ
ȱ =ȱȱ50.00cm3ȱ
ȱ ȱ 2.9ȱminȱ
ȱ =ȱ17.24cmȬ3minȬ1ȱ
ȱ
ȱ
Time/min
ACTIVITY 5.3
From the graph in Figure 5.8, calculate:
x The average speed of reaction in 3 minutes.
x The average speed of reaction from 3 minutes to 4 minutes.
x The average speed of reaction from 2 minutes to 4.5 minutes.ȱ
Tangentline
146

ȱ
ȱ
A
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Anotherȱ
reactionȱ
formicȱac
ȱ
Afterȱwe
weȱwillȱn
ȱ
Inȱ aque
(HCOOH
ȱ
ACTIVITY 5.
4
omȱtheȱgraphȱ
x Theȱinstan
x Theȱinstan
x Theȱinstan
whichȱtimeȱis
Fro
Atȱ
ȱ
S
5 SPEED OF
inȱFigureȱ5.9,
ntaneousȱspee
ntaneousȱspee
ntaneousȱspee
sȱtheȱreactianȱ
SELF-CHECK
K 5.2
henȱmagnesiu
reaseȱofȱvolum
.Whichȱ obser
eȱofȱreaction?ȱ
Wh
incr
Mg
rate
,ȱcalculate;
dȱofȱreactionȱ
dȱofȱreactionȱ
dȱofȱreactionȱ
theȱfastest?ȱA
umȱ (Mg)ȱ react
meȱinhydrog
rvableȱ change
ȱExplainȱwhy
exampleȱweȱ
isȱ actuallyȱ m
cid.ȱ
eȱhaveȱseenȱho
nowȱlearnȱtoȱw
ousȱ solution
H)ȱasȱfollows:
Molecula
progress
monitore
withȱaȱsp
theȱreact
ȱ
Theȱaver
concentr
Brƀȱ(aq)ȱ+ȱH
arȱ bromineȱ
ses,ȱ theȱ conce
edȱ easilyȱ byȱ
pectrometer.ȱ
tants.ȱ
rageȱrateȱofȱth
rationȱoverȱaȱc
TOPIC
REACTIONS
atȱ1ȱminute,
atȱ3ȱminutes,
atȱ4ȱminutes.
Atȱ1,ȱ2,ȱ3ȱorȱ4ȱm
tsȱwithȱdilute
enȱgasȱ(H2)ȱa
eȱwouldȱ you
y.ȱ
canȱlookȱatȱto
measuredȱ isȱ
ȱȱ
minutes?ȱ
edȱacid,ȱweȱ c
andȱtheȱdecre
uȱmeasureȱ toȱ
oȱunderstand
theȱ reaction
owȱthespeedȱ
writeȱspeedȱe
ofȱreactionisȱ
expressionsȱus
ns,ȱ molecular
:ȱ
rȱ bromineȱ (B
HCOOHȱ(aq)ȱȱȱ
ȱȱȱȱȱȱȱ2BrȬȱ(aq)ȱ
hasȱ aȱ distin
entrationȱofȱB
measuringȱ t
Noteȱthatȱtim
heȱreactionȱca
certainȱtimeȱin
ȱ
nctiveredȱ bro
Brƀȱ steadilyȱd
theȱmolecular
meȱzeroȱisȱthe
anȱbeȱdefined
nterval.ȱThatȱ
CHEMICAL R
canȱobserveȱa
easeȱinȱmassȱ
determineȱ th
dȱhowȱtheȱspe
nȱ ofȱ molecula
anȱ
ofȱ
heȱ
eedȱofȱaȱchem
arȱ bromineȱ w
measuredȱvia
singȱtheȱexpe
aȱExperimentȱ
rimentalȱdata
Br2)ȱ reactsȱ w
withȱ formicȱ a
+ȱ2H+ȱ(aq)ȱ+ȱC
COƀȱ(g)ȱ
ownȱ colour.ȱ
decreases.ȱThi
rȱ fadingȱ ofȱ b
eȱtimeȱjustȱaft
Asȱ theȱ react
isȱ changeȱ can
bromine’sȱ col
terȱtheȱmixing
dȱasȱtheȱchang
is,ȱ
geȱinȱtheȱreac
W 11
micalȱ
withȱ
5.1,ȱ
a.ȱ
acidȱ
tionȱ
nȱbeȱ
lourȱ
gȱofȱ
tantȱ
147

X T
12
TOPIC5 SPEE
Whereȱ Ǌȱ
concentra
quantity.ȱ
isȱneeded
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
SEL
ED OF CHEMIC
CAL REACTIO
Averageȱrateȱ=
LF-CHECK 5.
Theȱv
asȱfo
ȱ
Time
Volu
ȱ
i. D
ii. C
.3
volumeȱofȱO2ȱg
llows:ȱ
NS
Brƀ]ȱinitialȱ
nitialȱ
nitialȱ andȱ Ǌtȱ
ingȱtheȱtimeȱi
ionȱisȱaȱpositi
oȱmakeȱtheȱra
gasȱproducedȱd
eȱ(min)ȱ 0
umeȱ(cm3)ȱ 0
Drawȱaȱgraphȱo
Calculateȱtheȱa
minute.m
ȱ
5.3
Someȱche
toȱspeedȱu
Thereȱareȱ
(a) Part
(b) Con
(c) Pres
(d) Tem
(e) Cata
A
[Brƀ]ȱ =ȱ [Brƀ
ationȱofȱBrƀȱde
Butȱtheȱspeed
ȱinȱtheȱspeedȱ
ȱ 2ȱ
ȱ 60ȱ
ȱ[Brƀ]ȱfinalȱ–ȱ[B
ȱȱȱȱȱȱȱȱtfinalȱ–ȱtȱin
ȬȱǊȱ[Brƀ]ȱ
Ǌtȱ
ȱ
=ȱ tfinalȱ –ȱ tiniti
interval,ȱǊȱ[Br
iveȱquantity,ȱs
teȱpositive.ȱ
dueȱtoȱtheȱdeco
ofȱtheȱvolumeȱo
averageȱrateȱofȱ
FACTO
AȱREA
emicalȱreactio
upȱtheȱslowȱo
severalȱfacto
ticleȱsizeȱofȱth
ncentrationȱof
ssureȱofȱgaseo
mperature;ȱan
alysts.ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
= ȱ
]finalȱ –ȱ [Brƀ]in
ecreasesȱduri
dȱofȱthereacti
expressionȱto
ORSȱAFF
ACTION
ial.ȱ Becauseȱ t
rƀ]ȱisȱaȱnegati
soȱaȱminusȱsi
ompositionȱofȱH
theȱ
iveȱ
ignȱ
H2O2isȱrecorded
6ȱ 8
82ȱ 84
4ȱ 84ȱ
gainstȱtime.ȱ
theȱrateȱofȱreac
FECTING
nsȱareȱfast;ȱo
onesȱandȱslow
thersȱareȱslow
wȱdownȱtheȱfas
orsȱthatȱaffectȱ
theȱspeedȱofȱa
heȱreactants;ȱ
fȱtheȱreactants
ousȱreactants;
dȱ
s;ȱ
;ȱ
4ȱ
78ȱ
ofȱtheȱO2ȱgasȱa
reactionȱandȱt
dȱ
ctionȱatȱtheȱthir
GȱTHEȱS
10ȱ
rdȱ
SPEEDȱO
w.ȱSometimes
stȱones.ȱ
ȱreaction:ȱ
OFȱ
sȱchemistsȱwa
antȱ
148

Ifȱyouȱwantȱtoȱproduceȱasȱmuchȱofȱaȱproductȱasȱpossibleȱwithȱtheȱshortestȱ
amountȱofȱtimeviaaȱchemicalȱreaction,ȱyouȱmustȱconsiderȱtheȱkineticsȱofȱtheȱ
reaction.ȱ
5.3.1ȱ ȱEffectȱofȱParticleȱSizeȱofȱChemicalȱReactantsȱ
Reactionȱdependsȱ onȱ collisions.ȱTheȱmoreȱ surfaceȱ areaȱ onȱwhichȱ collisionsȱ
canȱoccur,ȱtheȱfasterȱtheȱreaction.ȱȱ
Youȱ canȱ holdȱ aȱ burningȱmatchȱ toȱ aȱ largeȱ chunkȱ ofȱ coalȱ andȱ nothingȱwillȱ
happen.ȱButȱifȱyouȱtakeȱthatȱsameȱpieceȱofȱcoal,ȱgrindȱitȱupȱvery,ȱveryȱfine,ȱ
throwȱitȱupȱintoȱtheȱair,ȱandȱstrikeȱaȱmatch,ȱyou’llȱgetȱanȱexplosionȱbecauseȱ
ofȱtheȱincreasedȱsurfaceȱareaȱofȱtheȱcoal.ȱȱȱ
Weȱ findȱ thatȱ smallȱ piecesȱ ofȱ solids,ȱ especiallyȱ powders,ȱ reactȱ fasterȱ thanȱ
largerȱpieces.ȱItȱisȱlikeȱfryingȱtwoȱpansȱofȱchips!ȱOneȱhasȱtheȱpotatoȱcutȱintoȱ
small,ȱthinȱchips.ȱTheȱotherȱpanȱhasȱbigger,ȱthickerȱchipsȱ(Figureȱ5.10).Whichȱ
chipsȱdoȱyouȱthinkȱwillȱbeȱcookedȱfirst?Whichȱchipsȱhaveȱtheȱlargerȱsurfaceȱ
area?ȱ
ȱ
Surfaceȱareaȱisȱaȱmeasureȱofȱhowȱmuchȱsurfaceȱisȱexposed.ȱSoȱforȱtheȱsameȱ
massofȱpotato,ȱsmallȱchipsȱhaveȱaȱlargerȱsurfaceȱareaȱthanȱbigȱchips.ȱ
ȱ
ȱ
ȱ
Figureȱ5.10:ȱSmallȱchipsȱwithȱlargerȱsurfaceȱareaȱ
ȱ
ȱȱȱȱȱȱȱȱȱ
149

14
LetȱusȱcarryȱoutȱExperimentȱ5.2ȱtoȱseeȱhowȱparticleȱsizeȱcanȱaffectȱtheȱspeedȱ
ofȱchemicalȱreaction.ȱ
ȱ
Experimentȱ5.2ȱ
ȱ
ȱ
ȱ
1. Repeatȱ Experimentȱ 5.1ȱ butȱ replaceȱ mediumȱ marbleȱ chipsȱ withȱ
smallȱmarbleȱchips.ȱ
ȱ
2. Theȱmassȱofȱsmallȱmarbleȱchips,ȱtheȱvolumeȱandȱconcentrationȱofȱ
hydrochloricȱacidȱusedȱareȱtheȱsame.ȱ
ȱ
3. Plotȱ theȱgraphȱofȱ theȱvolumeȱofȱ carbonȱdioxideȱ releasedȱagainstȱ
ȱ
timeȱonȱtheȱgraphȱpaperȱasȱinȱExperimentȱ5.1.ȱ
4. Calculateȱtheȱaverageȱspeedȱofȱreactionȱandȱinȱtheȱrateȱofȱreactionȱ
ȱ
inȱtheȱsecondȱminuteȱforȱthisȱexperiment.ȱ
5. Repeatȱ Experimentȱ 5.1ȱ onceȱ againȱ butȱ atȱ thisȱ timeȱ replaceȱ
ȱ
mediumȱmarbleȱchipsȱwithȱlargeȱmarbleȱchips.ȱ
ȱ
ȱ
ȱ SELF-CHECK ȱ
5.4
ȱ
From the figure given,
x Which size of marble
chips has the largest
ȱ
surface area?
x What would the graph
ȱ
look like if we use the
same mass of powdered
ȱ
calcium carbonate?
x Explain why.
ȱ
Now,ȱcanȱyouȱexplainȱhowȱtheȱparticleȱsizeȱofȱchemicalȱreactantsȱcanȱaffectȱ
theȱ speedȱ ofȱ reaction?Observeȱ Figureȱ 5.11ȱ toȱ helpȱ youȱ withȱ yourȱ
explanation.ȱ
150

ȱ
ȱȱ
(a) (b)
Figureȱ5.11:ȱ(a)ȱBiggerȱsizedȱreactant;ȱ(b)ȱSmallerȱsizedreactantȱ
Theȱsmallerȱtheȱsizeȱofȱreactant,ȱtheȱlargerȱisȱtheȱsurfaceȱareaȱexposed.ȱThisȱ
translatesȱtoȱanȱincreaseȱtoȱtheȱspeedȱofȱchemicalȱreaction.ȱ
ȱ
ACTIVITY 5.4
ȱ
Pourȱ800mlȱofȱwaterȱinȱtwoȱdifferentȱpots.Putȱ1kgȱofȱwholeȱchickenȱ
withoutȱcuttingȱitȱintoȱtheȱfirstȱpotȱandȱinȱanotherȱpotȱputȱanotherȱ
ȱ
1kgȱofȱchikenȱthatȱhadȱbeenȱcutȱinȱeight.Whichȱpotȱofȱchickenȱwillȱ
beȱdoneȱfirst?ȱExplainȱwhy.ȱ
ȱ
5.3.2ȱȱȱEffectȱofȱConcentrationȱofȱChemicalȱReactantsȱ
Increasingȱtheȱnumberȱofȱcollisionsȱwillȱspeedȱupȱtheȱreactionȱrate.ȱTheȱmoreȱ
reactantȱmoleculesȱthereȱareȱcolliding,ȱtheȱfasterȱtheȱreactionȱwillȱbe.ȱAsȱtheȱ
concentrationȱbecomesȱhigher,ȱtheȱnumberofȱmoleculesȱperunitȱvolumeȱalsoȱ
increasesȱ(Figureȱ5.12).ȱForȱexample,ȱaȱwoodȱsplintȱburnsȱmoderatelyȱinȱtheȱ
airȱ(20ȱpercentȱoxygen),ȱbutȱitȱburnsȱmuchȱfasterȱinȱpureȱoxygen.ȱ
151

16
ȱ
(a) (b)
ȱ
Figureȱ5.12:(a)ȱLowȱconcentration;ȱ(b)ȱHighȱconcentrationȱofȱreactantȱ
Inȱmostȱsimpleȱcases,ȱincreasingȱtheȱconcentrationȱofȱtheȱreactantsȱincreasesȱ
theȱspeedȱofȱreaction.ȱHowever,ȱifȱtheȱreactionȱisȱcomplexȱandȱhasȱaȱcomplexȱ
mechanismȱ (seriesȱ ofȱ stepsȱ inȱ theȱ reaction),ȱ thisȱ mayȱ notȱ beȱ theȱ case.ȱ
Determiningȱtheȱconcentrationȱeffectȱonȱtheȱspeedȱofȱreactionȱcanȱgiveȱyouȱ
cluesȱasȱtoȱwhichȱreactantȱisȱinvolvedȱinȱtheȱrate,ȱthusȱdeterminingȱtheȱstepȱ
ofȱtheȱmechanism.ȱ
Youȱ canȱdoȱ thisȱbyȱ testingtheȱ reactionȱwithseveralȱdifferentȱ concentrationsȱ
andȱobservingȱtheȱeffectȱonȱtheȱspeedȱofȱreactionȱasȱinȱExperimentȱ5.3.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
152

ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Experimentȱ5.3ȱ
ȱ
1. Usingȱaȱpencil,ȱmarkȱanȱ“X”ȱonȱaȱpieceȱofȱwhiteȱpaper,ȱasȱfollows:ȱ
ȱ
ȱ
ȱ
2. Usingȱtheȱ50cm³ȱmeasuringȱcylinder,ȱmeasureȱ50cm³ȱofȱ0.2ȱmolȱdmƉ³ȱ
sodiumȱthiosulphateȱsolutionȱandȱpourȱitȱintoȱaȱconicalȱflask.ȱPlaceȱ
theȱflaskȱonȱtheȱ“X”ȱmarkȱonȱtheȱwhiteȱpaper.ȱ
3. Measureȱ5cm³ȱofȱ1ȱmolȱdmƉ³ȱsulphuricȱacidȱwithȱaȱ10cm³ȱmeasuringȱ
cylinder.ȱ
4. Immediately,ȱ pourȱ theȱ sulphuricȱ acidȱ intoȱ theȱ conicalȱ flaskȱ
containingȱ 50cm³ȱ ofȱ sodiumȱ thiosulphateȱ solutionȱ andȱ shakeȱ theȱ
flask.ȱAtȱtheȱsameȱtime,ȱstartȱtheȱstopwatch.ȱ
5. Observeȱ theȱ yellowȱ precipitateȱ ofȱ sulphurȱ atȱ theȱ topȱ partȱ ofȱ theȱ
conicalȱ flask.ȱ Recordȱ theȱ timeȱ whenȱ theȱ “X”ȱ markȱ onȱ theȱ whiteȱ
paperȱisȱnoȱlongerȱvisible.ȱ
6. Repeatȱ theȱ experimentȱ usingȱ 50cm³ȱ ofȱ theȱ 0.4ȱ molȱ dmƉ³,ȱ ȱ 0.6molȱ
dmƉ³,ȱ 0.8ȱ molȱ dmƉ³ȱ andȱ 1.0ȱ molȱ dmƉ³sodiumȱ thiosulphateȱ
solution.Theȱ volumeȱ andȱ concentrationȱ ofȱ theȱ sulphuricȱ acidȱ usedȱ
areȱtheȱsame.ȱȱ
7. Plotȱtwoȱgraphs:ȱ
a)ȱȱ Graphȱofȱconcentrationȱofȱsodiumȱthiosulphateȱsolutionȱagainstȱ
time.ȱ
b)ȱȱ Graphȱ ofȱ theȱ concentrationȱ ofȱ sodiumȱ thiosulphateȱ solutionȱ
againstȱ1ȱTimeȱ
8. Calculateȱtheȱaverageȱspeedȱofȱreactionȱforȱallȱtheȱexperiment.ȱWhatȱ
canȱbeȱrepresentedȱbyȱ1ȱTime?ȱ
153

X T
18
TOPIC5 SPEE
Sodiumȱth
speedȱtoȱf
equationȱf
ED OF CHEMIC
hiosulphateȱs
formȱaȱyellow
forȱtheȱreactio
CAL REACTIO
olutionȱreacts
wȱprecipitateȱo
onȱis:ȱ
sȱwithȱdiluteȱ
ofȱsulphur,Sȱ(
SO4(aq)ȱȱÆȱȱN
2O3(aq)ȱȱ+ȱȱH2
Na2S2
http://ww
Theȱgraph
a) Gr
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ5.1
timeȱ
ȱ
ȱ
Na2SO4(aq)ȱȱ+ȱ
reȱ5.13:ȱTheȱyel
Figur
ww.sciencequi
hȱobtainedȱfro
raphȱofȱconce
Concentration
of sodium
thiosulphate
solution
(mol/dm3)
14:ȱGraphȱofȱc
llowȱprecipitat
[
Source:ȱ
mistry/rates/m
iz.net/lcchem
omȱExperimen
ntȱ5.3ȱshouldȱ
entrationȱofȱso
odiumȱthiosul
Time until
l cross can no long
ger be seen (s)
nȱofȱsodiumȱth
concentration
NS
sulphuricȱaci
Figureȱ5.8).ȱT
dȱatȱaȱveryȱlo
Theȱchemicalȱ
ȱS(s)ȱȱ+ȱȱSO2(g
ȱ
eȱofȱsulphurȱȱ
g)ȱȱ+ȱȱH2O(l)ȱ
matching/conc/
owȱ
m]ȱ
/rate_conc.htm
beȱshownȱasȱ
follows:ȱ
lphateȱsolutio
onȱagainstȱtim
ȱ
hiosulphateȱso
meȱ
olutionȱagain
stȱ
154

b)ȱ Graphȱofȱconcentrationȱofȱsodiumȱthiosulphateȱsolutionȱagainstȱtimeȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Concentration
of sodium
thiosulphate
solution
(mol/dm3)
1
Time (s-1)
Figureȱ5.15:ȱGraphȱofȱconcentrationȱofȱsodiumȱthiosulphateȱsolutionȱagainstȱ
timeȱ
FromȱExperimentȱ5.3,ȱtheȱtimeȱtakenȱforȱtheȱformationȱofȱaȱfixedȱquantityȱofȱ
sulphurȱtoȱcoverȱtheȱmarkȱ“X”ȱuntilȱitȱdisappearsȱfromȱsightȱcanȱbeȱusedȱtoȱ
measureȱtheȱspeedȱofȱreaction.ȱ
Speedȱofȱreactionȱisȱdirectlyȱproportionalȱto:ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
ȱ
1ȱ ȱ ȱ ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱtimeȱtakenȱforȱtheȱmarkȱ“X”ȱtoȱdisappearȱfromȱsightȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
155

20
5.3.3ȱ EffectȱofȱPressureȱofȱGaseousȱReactantsȱ
Theȱ pressureȱ ofȱ gaseousȱ reactantsȱ hasȱ basicallyȱ theȱ sameȱ effectȱ asȱ
concentration.ȱ Theȱ higherȱ theȱ reactantȱ pressure,ȱ theȱ higherȱ theȱ reactionȱ
speed.ȱThisȱisȱdueȱtoȱtheȱincreasedȱnumberȱofȱcollisionsȱ(Figureȱ5.16).ȱȱ
ȱ
ȱ
ȱ
ȱȱȱȱȱȱȱȱȱ
ȱ ȱ
ȱȱ
ȱ
Figureȱ5.16:ȱ(a)ȱLowȱpressureȱȱ;ȱ(b)ȱHighȱpressureȱ
ȱ
ȱ ȱ
5.3.4ȱ EffectȱofȱTemperatureȱȱ
Increasingȱ theȱ temperatureȱ causesȱmoleculesȱ toȱmoveȱ faster,ȱ soȱ thereȱ isȱ anȱ
increasedȱ chanceȱ ofȱ themȱ collidingȱ withȱ eachȱ otherȱ andȱ reacting.ȱ Butȱ
increasingȱ theȱ temperatureȱalsoȱ increasesȱ theȱaverageȱkineticȱ energyȱofȱ theȱ
molecules.ȱ
Figureȱ5.17showsȱanȱexampleȱofȱhowȱincreasingȱtheȱtemperatureȱaffectsȱtheȱ
kineticȱenergyȱofȱtheȱreactantsȱandȱincreasesȱtheȱreactionȱspeed.ȱ
ȱ
ȱ
156

ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱȱ
Figureȱ5.17:Theȱeffectȱofȱtemperatureȱonȱtheȱkineticȱenergyȱofȱreactantsȱ
Atȱanyȱgivenȱtemperature,ȱnotȱallȱofȱtheȱmoleculesȱareȱmovingȱwithȱtheȱsameȱ
kineticȱ energy.ȱAȱ smallȱ numberȱ ofȱmoleculesȱ areȱmovingȱ veryȱ slowȱ (lowȱ
kineticȱ energy),ȱwhileȱ aȱ fewȱ areȱmovingȱ veryȱ fastȱ (highȱ kineticȱ energy).ȱAȱ
vastȱ majorityȱ ofȱ theȱ moleculesȱ areȱ somewhereȱ inȱ betweenȱ theseȱ twoȱ
extremes.ȱ
Inȱ fact,ȱ temperatureȱ isȱ aȱ measureȱ ofȱ theȱ averageȱ kineticȱ energyȱ ofȱ theȱ
molecules.ȱ Asȱ youȱ canȱ seeȱ inȱ Figureȱ 5.17,ȱ increasingȱ theȱ temperatureȱ
increasesȱtheȱaverageȱkineticȱenergyȱofȱtheȱreactants,ȱessentiallyȱshiftingȱtheȱ
curveȱtoȱtheȱrightȱtowardsȱhigherȱkineticȱenergies.ȱ
Butȱ alsoȱ noticeȱ theȱ minimumȱ amountȱ ofȱ kineticȱ energyȱ neededȱ byȱ theȱ
reactantsȱ toȱ provideȱ theȱ activationȱ energyȱ (theȱ energyȱ requiredȱ toȱ getȱ aȱ
reactionȱgoing)ȱduringȱcollision.ȱTheȱreactantsȱhaveȱtoȱcollideȱatȱtheȱreactiveȱ
site,ȱbutȱtheyȱalsoȱhaveȱtoȱtransferȱenoughȱenergyȱtoȱbreakȱtheȱbondsȱsoȱthatȱ
newȱ bondsȱ canȱ beȱ formed.ȱ Ifȱ theȱ reactantsȱ doȱ notȱ haveȱ enoughȱ energy,ȱ aȱ
reactionȱwillȱnotȱoccurȱevenȱifȱtheȱreactantsȱdoȱcollideȱatȱtheȱreactiveȱsite.ȱ
Noticeȱ thatȱ atȱ theȱ lowerȱ temperature,ȱ veryȱ fewȱ ofȱ theȱ reactantȱmoleculesȱ
haveȱ theȱ minimumȱ amountȱ ofȱ kineticȱ energyȱ neededȱ toȱ provideȱ theȱ
activationȱenergy.ȱAtȱtheȱhigherȱtemperature,ȱmanyȱmoreȱmoleculesȱpossessȱ
157

22
theȱminimumȱ amountȱ ofȱ kineticȱ energyȱ needed,ȱwhichȱmeansȱ aȱ lotȱmoreȱ
collisionsȱwillȱbeȱenergeticȱenoughȱtoȱleadȱtoȱreaction.ȱ
Increasingȱ theȱ temperatureȱnotȱonlyȱ increasesȱ theȱnumberȱofȱ collisionsȱbutȱ
alsoȱ increasesȱ theȱ numberȱ ofȱ collisionsȱ thatȱ areȱ effectiveȱ—ȱ thatȱ transferȱ
enoughȱenergyȱtoȱcauseȱaȱreactionȱtoȱtakeȱplaceȱ(Figureȱ5.18).ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ5.18:ȱEffectȱofȱtemperatureȱonȱtheȱreactionȱbetweenȱparticleȱAȱandȱparticleȱBȱ
ȱ
ACTIVITY 5.5
ȱ
Designȱ andȱ carryȱ outȱ anȱ experimentȱ toȱ studyȱ theȱ effectȱ ofȱ
ȱ
temperatureȱonȱtheȱrateȱofȱreaction.ȱTheȱvariousȱtemperaturesȱthatȱ
areȱ suggestedȱ forȱ thisȱ experimentȱ areȱ 30°C,ȱ 35°C,ȱ 40°C,ȱ 45°Cȱ andȱ
ȱ
50°C.ȱ Theȱmaterialsȱ andȱ apparatusȱ suppliedȱ areȱ asȱ shownȱ inȱ theȱ
following:ȱ
ȱ
Materials:ȱ1ȱmolȱdmƉ³ȱsulphuricȱacid,ȱH2SO4,ȱ0.2ȱmolȱdmƉ³ȱsodiumȱ
ȱ
thiosulphateȱsolution,ȱNa2S2O4,ȱwhiteȱpaper.ȱ
Apparatus:ȱ 100cm³ȱ conicalȱ flask,ȱ 50cm³ȱ measuringȱ cylinders,ȱ
ȱ
stopwatch,ȱBunsenȱburner,ȱwireȱgauze,ȱtripodȱstand,ȱthermometer.ȱ
ȱ
ȱ
ȱ
Calculateȱtheȱrateȱofȱreactionȱatȱtheȱthirdȱminute.ȱ
ȱ
ȱ
ȱ
158

5.3.5ȱ ȱȱ
Effectȱofȱ
sȱ areȱ substan
dȱ atȱ theȱ endȱ o
yȱloweringȱthe
Catalysts
changed
speedȱby
Figureȱ 5
provideȱ
thatmore
reactionȱ
5.19ȱ represent
theȱ activatio
eȱmoleculesȱw
willȱbeȱfaster
sȱlowerȱtheȱac
Catalysts
Providingȱaȱsu
Providingȱanȱ
oȱgoȱthrough)
i. P
ii. P
Figureȱ5.19:ȱE
to
Weȱ obse
reactionȱ
doesȱnot
actsȱasȱaȱ
ȱ
ȱ
ervedinȱ study
speedȱdepen
tȱ appearȱ inȱ th
catalystȱforȱth
A
a
catalyst is a sub
chemical reactio
TOPIC
sȱȱ
Catalysts
5 SPEED OF
ncesȱ thatȱ inc
ofȱ theȱ reactio
eȱactivationȱe
creaseȱ theȱ re
onȱ themselve
nergyȱforȱthe
tsȱ theȱminim
onȱ energyȱ fo
willȱ thenȱ hav
r.ȱ
mumȱ amountȱ
orȱ theȱ reactio
veȱ theȱminim
Energyȱprofileȱd
diagramȱshow
ctivationȱener
urfaceȱandȱori
alternativeȱm
)ȱwithȱaȱlower
yingȱ theȱdeco
ndsȱonȱtheȱco
heȱoverallȱ eq
hatȱreaction.ȱ
bstance that increa
on without being c
ȱ
rgyȱofȱaȱreacti
ientation;ȱand
mechanismȱ (se
rȱactivationȱe
ompositionȱ of
ncentrationȱo
quation.ȱWeȱn
ases the speed of
consumed.
CHEMICAL R
REACTIONS
eactionȱ speed
s.ȱ Theyȱ incre
eȱreaction.ȱ
dȱ withoutȱ be
easeȱ theȱ react
ofȱ kineticȱ en
onȱ withȱ catal
mumȱ energyȱ n
eingȱ
tionȱ
nergyȱ needed
lyst.ȱ Thisȱ me
needed,ȱ thusȱ
sȱtheȱactivation
ionȱinȱtwoȱwa
dȱ
eriesȱofȱ steps
nergy.ȱ
fȱhydrogenȱp
ofȱiodineȱions
notedȱ thereȱ th
ȱ
nȱenergyȱ
ays:ȱ
dȱ toȱ
eansȱ
theȱ
sȱforȱtheȱ react
W 23
tionȱ
theȱ
ghȱitȱ
n,ȱ IȬȱ
peroxideȱ thatȱ
s,IȬ,eventhoug
hatȱ iodineȱ ion
159

24
Theȱ catalystȱmayȱ reactȱ toȱ formȱ anȱ intermediate,ȱ butȱ itȱ isȱ regeneratedȱ inȱ aȱ
subsequentȱ stepȱofȱtheȱreaction.ȱInȱtheȱlaboratoryȱpreparationȱofȱmolecularȱ
oxygen,ȱaȱsampleȱofȱpotassiumȱchlorateȱisȱheated,ȱasȱshownȱinȱFigureȱ5.19,ȱ
andtheȱreactionȱisȱnotedȱasȱfollows:ȱ
2KCIOƁȱ(s)ȱȱȱȱȱȱȱȱȱȱȱǊȱȱȱȱȱȱȱȱȱȱȱȱȱ2KCIȱ(s)ȱ+ȱ3Oƀȱ(g)ȱ
However,ȱthisȱthermalȱdecompositionȱwillȱoccurveryȱslowlyȱinȱtheȱabsenceȱ
ofȱ aȱ catalyst.ȱ Theȱ rateȱ ofȱ decompositionȱ canȱ beȱ increasedȱ dramaticallyȱ byȱ
addingȱaȱsmallȱamountȱofȱtheȱcatalystȱmanganeseȱ(MnOƀ),ȱaȱpowderyȱblackȱ
substance.AllȱofȱtheȱMnOƀȱcanȱbeȱrecoveredȱatȱtheȱendȱofȱtheȱreaction,ȱjustȱasȱ
allȱofȱtheȱiodineȱions,IȬ,remainȱfollowingȱHƀOƀȱdecomposition.ȱ
Regardlessȱofȱitsȱnature,ȱaȱcatalystȱspeedsȱupȱaȱreactionȱbyȱprovidingȱaȱsetȱofȱ
elementaryȱstepsȱwithȱaȱmoreȱfavourableȱkineticsȱthanȱthoseȱthatȱexistȱinȱitsȱ
absence.ȱTheȱsmallerȱtheȱactivationȱenergy,ȱEೈ,ȱtheȱgreaterȱtheȱrate.ȱInȱmanyȱ
cases,ȱaȱcatalystȱincreasesȱtheȱrateȱbyȱloweringȱtheȱactivationȱenergyȱforȱtheȱ
reaction.ȱ
ȱ
LetȱusȱcarryȱoutȱExperimentȱ5.4ȱtoȱstudyȱtheȱeffectȱofȱcatalystȱonȱtheȱspeedȱofȱ
reaction.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
160

ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Experimentȱ5.4ȱ
ȱ
1. Fillȱtheȱbasinȱandȱsmallȱmeasuringȱcylinderȱwithȱwater.ȱInvertȱtheȱ
measuringȱcylinderȱintoȱtheȱbasinȱthatȱisȱfilledȱwithȱwaterȱ(Figureȱ
5.20).ȱ
2. Measureȱ50cm³ȱofȱ20Ȭvolumeȱofȱhydrogenȱperoxideȱsolutionȱusingȱ
aȱmeasuringȱcylinderȱandȱpourȱitȱintoȱtheȱconicalȱflask.ȱ
3. Putȱ aȱ weighingȱ bottleȱ containingȱ aȱ halfȱ spatulamanganeseȱ (IV)ȱ
oxideȱpowderȱintoȱtheȱhydrogenȱperoxideȱsolution.ȱ
4. Immediatelyȱ coverȱ theȱ conicalȱ flaskȱwithȱ theȱ rubberȱ stopperȱandȱ
shakeȱtheȱflaskȱslowly.ȱStartȱtheȱstopwatchȱatȱtheȱsameȱtime.ȱ
5. Recordȱ theȱ volumeȱ ofȱ oxygenȱ releasedȱ everyȱ 30ȱ secondsȱ forȱ 300ȱ
secondsȱ(5ȱminutes).ȱ
6. Repeatȱ theȱ experimentȱ byȱ addingȱ aȱ spatulaȱ ofȱ manganeseȱ (IV)ȱ
oxideȱpowder.ȱ
7. Theȱvolumeȱandȱconcentrationȱofȱtheȱhydrogenȱperoxideȱsolutionȱ
usedȱareȱtheȱsame.ȱ
8. Then,ȱ plotȱ twoȱ graphsȱ ofȱ theȱ volumeȱ ofȱ gasȱ againstȱ timeȱ withȱ
differentȱamountȱofȱcatalyst,ȱonȱtheȱsameȱgraphȱpaper.ȱ
9. Calculateȱ theȱ averageȱ rateȱ ofȱ reactionȱ forȱ eachȱ experiment.ȱDoesȱ
theȱamountȱofȱcatalystȱincreaseȱtheȱrateȱofȱreaction?ȱ
ȱ
Figureȱ5.20:ȱSetȬupȱofȱtheȱapparatusȱforȱExperimentȱ5.4ȱ
161

26
Theȱ graphȱ obtainedȱ fromȱ Experimentȱ 5.4ȱ shouldȱ beȱ asȱ shownȱ inȱ theȱ
following:ȱ
ȱ
ȱ
Figureȱ5.21:ȱTheȱeffectȱofȱcatalystȱonȱtheȱspeedȱofȱreactionȱofȱhydrogenȱperoxideȱ
solutionȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
SELF-CHECK 5.5
Europeanȱ regulationsȱ stateȱ thatȱ allȱ newȱ
carsȱ haveȱ toȱ beȱ fittedȱ withȱ catalyticȱ
convertersȱasȱpartȱofȱtheirȱexhaustȱsystem.ȱ
ȱ
UsingȱtheȱInternetȱand/orȱotherȱresources,ȱ
explainȱhowȱ catalyticȱ convertersȱwork.Inȱ
yourȱ explanation,ȱ stateȱ theȱ nameȱ ofȱ
catalystȱused.ȱ
ACTIVITY 5.6
Theȱfollowingȱtwoȱsetsȱofȱexperimentsȱareȱcarriedȱout:ȱ
Setȱ Iȱ –ȱ 1gȱ ofȱ granulatedȱ zincȱ isȱ addedȱ toȱ 30cm3ȱ ofȱ 0.5ȱ mol/dm3ȱ
hydrochloricȱacidȱ
Setȱ IIȱ Ȭȱ 1gȱ ofȱ granulatedȱ zincȱ isȱ addedȱ toȱ 30cm3ȱ ofȱ 0.5ȱ mol/dm3ȱ
hydrochloricȱacidȱandȱ2cm3ȱofȱ1ȱmol/dm3ȱcopper(II)ȱsulphateȱ
solution.ȱ
ExplainȱwhyȱtheȱinitialȱrateȱofȱsetȱIIȱisȱhigherȱthanȱthatȱofȱsetȱIȱusingȱ
theȱcollisionȱtheory.
162

THEȱEFFECTȱOFȱACTIVATIONȱ
ENERGYȱONȱTHEȱSPEEDȱOFȱAȱ
REACTIONȱ
5.4
Allȱmoleculesȱpossessȱaȱcertainȱminimumȱamountȱofȱenergy.ȱTheȱenergyȱcanȱ
beȱ inȱ theȱ formȱ ofȱ kineticȱ energyȱ and/orȱpotentialȱ energy.ȱWhenȱmoleculesȱ
collide,ȱtheȱkineticȱenergyȱofȱtheȱmoleculesȱcanȱbeȱusedȱtoȱstretch,ȱbendȱandȱ
ultimatelyȱbreakȱtheȱbonds,ȱleadingȱtoȱchemicalȱreactions.ȱȱ
Ifȱmoleculesȱ areȱ movingȱ tooȱ slowlyȱwithȱ littleȱ kineticȱ energy,ȱ orȱ collidedȱ
withȱanȱimproperȱorientation,ȱtheyȱwillȱnotȱreactȱandȱsimplyȱbounceȱoffȱeachȱ
other.ȱHowever,ȱifȱtheȱmoleculesȱareȱmovingȱatȱaȱfastȱenoughȱvelocityȱwithȱaȱ
properȱ collisionȱ orientation,ȱ suchȱ asȱ theȱ kineticȱ energyȱ uponȱ collisionȱ isȱ
greaterȱ thanȱ theȱminimumȱ energyȱ barrier,ȱ thenȱ aȱ reactionȱwillȱ occur.ȱ Theȱ
minimumȱenergyȱbarrierȱthatȱmustȱbeȱmetȱforȱaȱchemicalȱreactionȱtoȱhappenȱ
isȱcalledȱtheȱactivationȱenergy,ȱEa.ȱItȱcanȱbeȱrepresentedȱbyȱtryingȱtoȱpushȱaȱ
stoneȱtoȱtheȱotherȱsideȱasȱshownȱinȱFigureȱ5.22.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ5.23:ȱTheȱmanȱisȱtryingȱtoȱpushȱtheȱstoneȱfromȱpointȱAȱtoȱpointȱBȱ
[Source:ȱhttp://sites.tenafly.k12.nj.us/~shilfstein/demo_notes.htm]ȱ
Theȱ reactionȱ pathwayȱ canȱ beȱ observedȱ inȱ Figureȱ 5.23.ȱ Inȱ orderȱ toȱ getȱ theȱ
productȱ toȱ react,ȱ theȱ reactantȱ hasȱ toȱ overcomeȱ theȱ activationȱ energy,ȱ orȱ aȱ
newȱ productȱ cannotȱ beȱ achievedȱ ifȱ itȱ doesȱ notȱ haveȱ theȱ sameȱ amountȱ ofȱ
energy.ȱ
163

X T
28
a
Ea
ED OF CHEMIC
ithȱhigherȱactiv
ationȱenergy,ȱE
ercomeȱbyȱtheȱ
atȱtheȱreactionȱc
NS
E
Ea
vationȱenergyȱ(
Ea,ȱisȱtheȱenergy
collidingȱparti
canȱoccur!ȱ
ationȱenergy,
alȱreaction,ȱth
stem.ȱ Ifȱ theȱm
ndȱ thisȱ energ
willȱhappenȱan
1.
2.
ȱ
ȱ
TOPIC5 SPEE
Figureȱ5.2
ȱ
ȱ
ȱ
24:ȱReactionȱwi
Theȱactiva
aȱchemica
ofȱ theȱsys
energyȱ an
reactionȱw
Inȱ otherȱ
reactionȱ t
reaction,ȱt
state.ȱ The
reaction.ȱ
ȱȱȱȱ
ȱ
ȱ
ȱ
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beȱove
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eȱ lowerȱ theȱ
mustȱȱ
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thanȱ theȱ trans
willȱform.ȱȱ
higherȱ theȱ a
dȱ viceȱ versa.ȱ
nȱenergyȱisȱlo
activationȱ en
SELF-CHEC
CK 5.5
activationȱenerg
nsitionȱstateȱ(
dȱasȱtheȱhigh
collideȱwithȱ
sitionȱ stateȱ e
activationȱ ene
However,ȱ if
oweredȱbecau
nergy,ȱ theȱ hig
nȱenergyȱcanȱb
oȱȱovercomeȱt
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Activation
weȱneedȱto
Whatȱisȱth
CAL REACTIO
ȱ
ȱ
ȱ
(b)ȱ
ȱ
gyȱ
Figureȱ5.24).ȱ
estȬenergyȱsta
enoughȱkine
nergy,ȱ thenȱ t
ergy,ȱ theȱ har
fȱ aȱ catalystȱ i
useȱofȱtheȱlow
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beȱdecreased
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state?ȱ
Inȱ
ateȱ
eticȱ
theȱ
rderȱ itȱ isȱ for
sȱ addedȱ toȱ t
weredȱtransiti
eedȱ ofȱ chemi
byȱaddingȱaȱ
nȱenergy?ȱ
rȱ aȱ
theȱ
ionȱ
calȱ
catalyst.ȱWhy
yȱdoȱ
164

•ȱ The
rea
ȱ
•ȱ Ob
cal
ȱ
•ȱ The
ofȱt
ȱ
•ȱ The
tim
ȱ
x Fac
i.
ii.
iii.
iv.
v.ȱȱ
x Act
pla
ȱ
ȱ
Activatio
Catalystȱ
Collision
Concentr
Effectȱ
Instantan
ȱȱȱ
eȱ speedȱ ofȱ c
action.ȱItȱisȱaȱm
bservableȱ cha
culateȱtheȱspe
eȱaverageȱspe
time.ȱ
eȱinstantaneo
me.ȱ
ctorsȱthatȱaffe
Particleȱ siz
largerȱtheȱ
Concentra
numberȱof
Pressureȱ
speedȱofȱre
Temperatu
ofȱparticleȱ
Catalystsȱs
tivationȱ ener
ace.ȱ
onȱenergyȱ
nȱ
rationȱ
neousȱspeedȱo
TOPIC
chemicalȱ rea
measurement
angesȱ ofȱ reac
eedȱofȱreactio
eedȱofȱreactio
ousȱspeedȱofȱ
ectȱtheȱspeedȱo
zeȱofȱ theȱ reac
totalȱsurfaceȱa
ationȱofȱtheȱre
fȱparticleȱperȱu
ofȱ gaseousȱ
eaction.ȱ
ure–ȱhigherȱte
andȱincrease
speedȱupȱtheȱ
gyȱmustbeȱov
ofȱreactionȱ
5 SPEED OF
CHEMICAL R
actionȱ canȱ al
tȱofȱhowȱfastȱa
lsoȱ beȱ stated
areactionȱtake
ctantsȱ andȱ pr
n.ȱ
roductsȱ canȱ
onȱisȱtheȱspee
edȱofȱreactionȱ
reactionȱisȱth
heȱspeedȱofȱre
ofȱreactionȱar
e:ȱ
ctants–ȱ theȱ sm
area.ȱ
actants–ȱasȱth
unitȱvolumeȱi
reactants–hig
mallerȱ theȱ siz
heȱconcentrati
increases.ȱȱ
gherȱ pressur
emperatureȱw
ȱtheȱspeedȱofȱ
reactionȱwith
willȱincreaseȱth
reaction.ȱ
houtȱundergoi
vercomeȱ forȱ
theȱ chemical
clesȱsizeȱ
sureȱ
uctȱ
tantȱ
dȱofȱreaction
sitionȱstateȱ
Partic
Press
Produ
React
Speed
Trans
ȱ
REACTIONS
dȱ asȱ theȱ rate
esȱplace.ȱȱ
beȱ measured
overȱanȱinter
eactionȱataȱgi
zeȱofȱparticleȱ
ionȱincreases,
reȱ increasesȱ
heȱkineticȱene
ingȱchange.ȱ
ȱ reactionȱ toȱ t
W 29
ȱ
eȱ ofȱ
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ivenȱ
theȱ
,ȱtheȱ
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ergyȱ
takeȱ
165

X T
30
ȱ
Atkins,ȱP.
ȱ
Chang,ȱR.
ȱ ȱ
Earl,ȱB.,ȱ&
ȱ ȱ ȱ
Eng,ȱ N.ȱ H
Pela
ȱ ȱ ȱ
Moore,ȱJ.T
ȱ
Odufalu,ȱ
Retrieved
http://che
eaction_R
ȱȱ
TOPIC5 SPEE
ED OF CHEMIC
W.ȱ(1994).ȱPhy
.ȱ(1989).ȱȱChem
ȱWilford,ȱD.ȱ
H.,&ȱ Lim,ȱ Y
angi.ȱ
T.Chemistryȱfo
F.,ȱ Chacha,ȱ
dȱfromȱ
emwiki.ucdav
Rateȱ
ȱ
CAL REACTIO
ysicalȱchemistr
ry.ȱȱOxford:ȱO
mistry.ȱNewȱY
NS
xfordȱUnivers
wȬHill.ȱ
York:ȱMcȱGraw
(2009).ȱȱIGCS
Y.ȱ C.ȱ (2007).ȱ
Eȱchemistry.ȱU
sityȱPress.ȱ
Education.ȱ
UK:ȱHodderȱE
Focusȱ superȱ
orȱdummies.Riv
chemistry.ȱ Ba
verȱStȱHobok
P.,ȱ Mudda,ȱ
vis.edu/Physic
angi:ȱ Penerbit
y.ȱ
ken,ȱNJȱ:ȱWiley
G.ȱ &ȱ Iskan
tanȱ
).ȱ Reactionȱ ra
darȱ A.ȱ (n.d.)
cal_Chemistry
y/Kinetics/Re
ate.ȱ
eaction_Rates
/R
166

TOPIC 6: HYDROCARBON COMPOUNDS I
TOPIC 7: HYDROCARBON COMPOUNDS II
Readings
Rose Marie Gallgher (1997). Complete Chemistry, Oxford Universiti Press, UK.
Ralph A. Burns (2003). Fundamentals of Chemistry, Prentice Hall, Ney Jersey
Bryan Milner, Jean Martin, John Mills (2002). Core Chemistry, Cambridge
Universiti Press
J. G. R. Briggs (2003). Chemistry Insight, Pearson Education Asia Pte. Ltd.
Singapore
J.G. R. Briggs (2003). Science in Focus Chemistryfor GCE ‘O’ Level,
Pearson Education Asia Pte.Ltd. Singapore.
Bahagian Pendidikan Guru, Kementerian Pendidikan Malaysia. (1995) Buku
Sumber Pengajaran Pembelajaran Sains Sekolah Rendah, Jilid 3: Strategi
Pengajarandan Pembelajaran Sains. Projek PIER Bahagian Pendidikan Guru
sertadan Bahagian Perancangan dan Penyelidikan Dasar Pendidikan, Kuala
Lumpur
Whitten, K.W., Davis, R.E.,Peck,M.L and Stanley, GG. (2008). Chemistry
(Ninth Edition).2010 Brooks/Cole.
Keywords
. alcohols and phenols
. primary, secondary and tertiary
. polymerization
. polymers
. condensation reaction
. condensation polymerizations
. nylon
. carboxylic acids
169

Learning Outcomes
At the end of this Topic, the learner will be able to;
1. Ability to differentiate between alcohols and phenols.
2. Ability to differentiate between primary, secondary and tertiary alcohols.
Illustrate by writing names and formulas for three alcohols of each type.
3. Explain the trends in boiling points and solubilities of alcohols in water.
4. Describe the physical properties of alcohol.
5. Describe some uses of alcohol.
6. Describe polymerization, write equations for three polymerization reactions,
explain two classes of polymers and naming three polymers commonly found
in the classroom and give their uses or functions.
7. Give an example of a condensation reaction. Name the essential feature of
monomers used in the condensation polymerizations.
8. Define nylon? Describe in your own words how nylon is prepared.
9. Define carboxylic acids. Write structural formals for five carboxylic acids.
10. Define esters. Write structural formulas for four esters.
Study Questions
Task 1 : Read section 27-9 Alcohols and phenols and answer questions 1 – 3
(a) What do you understand about alcohols and phenols?
(b) How do they differ?
(c ) Why are alcohols and phenols be viewed as derivatives of
hydrocarbons?
Task 2 : Can you differentiate between primary, secondary and tertiary alcohols?
Illustrate by writing names and formulas for three alcohols of each type.
Task 3 : Refer to Table 27-8. Explain the trends in boiling points and solubilities
of alcohols in water.
170

Task 4 : Describe the physical properties of alcohol. Refer to Page 998-999.
Task 5 : Describe some uses of alcohol. Refer to Page 999 for the information.
Task 6 : Refer to page 1020-1024 for questions 6 - 8. In your own words,
(i) describe polymerization.
(ii) write equations for three polymerization reactions.
(iii) explain two classes of polymers.
(iv) Name three polymers commonly found in the classroom and
give their uses or functions.
Task 7 : Give an example of a condensation reaction. Name the essential feature
of monomers used in the condensation polymerizations.
Task 8 : What is nylon? Describe in your own words how nylon is prepared.
Task 9 : Refer to section 27-13 Carboxylic acids for questions 9 - 10. Define
carboxylic acids. Write structural formals for five carboxylic acids.
Task 10 : Define esters. Write structural formulas for four esters.
171

ȱȱȱ
ȱ ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
Topiic
8
X Natural
Materials and
Manufactured
or Man-made
Materials
Byȱtheȱendȱofȱthisȱtopic,ȱyouȱshouldȱbeȱableȱto:
1. Defineȱmaterial;ȱ
2. Describeȱeachȱtypeȱofȱmaterials;ȱ
3. Explainȱtheȱpropertiesȱofȱmaterials;ȱ
4. Stateȱtheȱimportanceȱofȱmaterials;ȱ
5. Compareȱnaturalȱmaterialsȱandȱmanufacturedȱmaterials;ȱ
6. Describeȱhowȱtoȱpreserveȱourȱnaturalȱmaterials;ȱ
7. Describeȱcompositeȱmaterials;ȱandȱ
8. Discussȱ theȱmaterialsȱ inȱ industryȱ inȱ theȱ contextȱ ofȱ soap,ȱ naturalȱ and
syntheticȱrubber,ȱnaturalȱandȱsyntheticȱfibreȱandȱplastics.ȱ
ȱ
LEARNING OUTCOMES
275

TOPIC 8 NATURAL MATERIALS MANUFACTURED OR MAN-MADE MATERIALS
71
X INTRODUCTION
Materialsȱareȱtheȱthingsȱthatȱyouȱcanȱobserveȱallȱaroundȱyou.ȱFromȱfallingȱrainȱ
toȱ plantsȱ andȱ humanȱ beings,ȱ fromȱwindowȱ curtainsȱ toȱ floorȱmatsȱ andȱ fromȱ
computersȱ toȱ printingȱ materials,ȱ theseȱ areȱ allȱ materials.ȱ Theȱ airȱ thatȱ youȱ
breatheȱinȱandȱoutȱisȱalsoȱaȱmaterial.ȱȱ
ȱ
Materialsȱareȱveryȱusefulȱtoȱhumanȱbeingsȱforȱtheirȱsurvival.ȱTheyȱnotȱonlyȱuseȱ
naturalȱmaterialsȱbutȱalsoȱcreateȱnewȱmaterialsȱinȱorderȱtoȱfulfilȱtheirȱneeds.ȱ
DEFINITION, PROPERTIES AND
IMPORTANCE OF MATERIALS
Aȱcloudȱisȱseenȱasȱaȱbulkȱofȱmovingȱobjectȱinȱtheȱair.ȱWhenȱitȱisȱveryȱheavy,ȱitȱ
startsȱ toȱ dropȱ tinyȱ dropletsȱ ofȱ water.ȱ Whenȱ theȱ sunȱ shinesȱ onȱ theȱ waterȱ
droplets,ȱitȱturnsȱtoȱvapour.ȱHaveȱyouȱeverȱthoughtȱofȱtheȱprocessesȱthatȱoccurȱ
inȱthisȱevent?ȱ
ȱ
Thisȱeventȱisȱjustȱoneȱinȱaȱthousandȱofȱeventsȱthatȱinvolveȱmaterials.ȱMaterialsȱ
areȱtheȱthingsȱallȱaroundȱyou.ȱMaterialsȱhaveȱmassȱandȱoccupyȱspace.ȱGases,ȱ
woods,ȱplastics,ȱfoods,ȱanimalsȱandȱwaterȱareȱallȱexamplesȱofȱmaterials.ȱ
ȱȱ
Accordingȱ toȱ theȱ ancientȱ Greek,ȱ thereȱ shouldȱ beȱ fourȱ thingsȱ toȱmakeȱ upȱ aȱ
substance.ȱTheseȱfourȱthingsȱareȱearth,ȱfire,ȱairȱandȱwater.ȱTheȱGreeksȱbelievedȱ
thatȱ theseȱ fourȱ thingsȱmixȱ togetherȱ inȱ differentȱ amountsȱ toȱmakeȱ differentȱ
materials.ȱ
8.1.1 Definition of Materials
Whatȱisȱmaterial?ȱMaterialȱisȱdefinedȱasȱfollows.ȱȱ
ȱ
ȱ
8.1
Materialȱ isȱ madeȱ upȱ ofȱ thousandsȱ ofȱ smallȱ particles,ȱ notȱ visibleȱ toȱ theȱ
nakedȱeye,ȱcalledȱatoms.ȱTheȱcompositionȱofȱatomsȱinȱtheȱmaterialȱmakesȱitȱ
differentȱfromȱoneȱanother.ȱȱ
276

XTOPIC 8 NATURAL MATERIALS MANUFACTURED OR MAN-MADE MATERIALS
72
Basedȱ onȱ theseȱ compositionsȱ ofȱ atom,ȱ materialȱ canȱ beȱ dividedȱ intoȱ threeȱ
categories:ȱelement,ȱcompoundȱandȱmixture.ȱ
(i) Elementȱ
ȱ
Anȱelementȱisȱtheȱsimplestȱsubstanceȱofȱaȱmaterial.ȱItȱcannotȱbeȱbrokenȱ
downȱ orȱ separatedȱ byȱ chemicalȱ orȱ physicalȱmethodsȱ intoȱ anyȱ simplerȱ
components.ȱAnȱ elementȱ isȱmadeȱ upȱ ofȱ onlyȱ oneȱ typeȱ ofȱ atom.ȱ Someȱ
elementsȱ haveȱ atomsȱ ofȱ theȱ sameȱ types,ȱwhichȱ areȱ combinedȱ toȱ formȱ
molecules.ȱThereȱareȱ112ȱtypesȱofȱelements,ȱinȱwhichȱ92ȱofȱtheseȱelementsȱ
occurȱnaturallyȱinȱtheȱearthȱandȱ20ȱareȱcreatedȱbyȱscientists.ȱȱ
ȱ
Elementsȱ canȱbeȱgroupedȱ intoȱmetalsȱ andȱnonȬmetals.ȱGold,ȱ zinc,ȱ iron,ȱ
aluminium,ȱ oxygen,ȱ carbon,ȱ hydrogenȱ andȱ nitrogenȱ areȱ examplesȱ ofȱ
elements.ȱ
ȱ
Figureȱ 8.1ȱ showsȱ theȱ atomȱofȱ anȱ elementȱwithȱ itsȱnucleusȱ atȱ theȱ centreȱ
andȱelectronsȱmovingȱaroundȱtheȱnucleus.ȱ
Figureȱ8.1:ȱTheȱatomȱofȱanȱelementȱ
ȱ
ȱ
ȱ
ȱ
277

73
(b)ȱ CombinedȱElementsȱ
ȱ
ȱ Thereȱareȱtwoȱtypesȱofȱcombinedȱelementsȱ–ȱcompoundsȱandȱmixtures.ȱ
ȱ
(i) Compoundȱ
ȱ Twoȱorȱmoreȱelementsȱcanȱbeȱcombinedȱtogetherȱchemicallyȱtoȱformȱ
aȱ newȱ materialȱ calledȱ aȱ compound.ȱ Aȱ moleculeȱ isȱ theȱ smallestȱ
particleȱ inȱ aȱ compound.ȱWaterȱ isȱ anȱ exampleȱ ofȱ aȱ compound.ȱ Aȱ
waterȱmoleculeȱ isȱmadeȱupȱofȱoneȱoxygenȱatomȱandȱ twoȱhydrogenȱ
atoms,ȱwhichȱareȱcombinedȱchemicallyȱ(seeȱFigureȱ8.2).ȱ
ȱ
Oxygen atom
Figureȱ8.2:ȱWaterȱmoleculeȱ
Tableȱ8.1ȱshowsȱseveralȱtypesȱofȱcompoundsȱandȱitsȱelements.ȱ
ȱ
ȱ
Hydrogen
atoms
ACTIVITY 8.1
Lookȱoutsideȱyourȱlaboratory.ȱIdentifyȱtheȱobjectsȱandȱlistȱdownȱtheȱ
objects.ȱTheyȱareȱmadeȱofȱdifferentȱ typesȱofȱmaterials.ȱ ȱMostȱofȱ theȱ
materialsȱareȱmadeȱfromȱaȱcombinationȱofȱelements.ȱSomeȱareȱmadeȱ
ofȱonlyȱoneȱtypeȱofȱelement.ȱCanȱyouȱguessȱwhichȱobjectsȱareȱmadeȱ
ofȱonlyȱoneȱelement?ȱCanȱyouȱnameȱtheȱelementȱinȱeachȱcase?ȱWriteȱ
downȱyourȱfindings.ȱ ȱ
278

74
ȱ Tableȱ8.1:ȱȱSeveralȱTypesȱofȱCompoundsȱ
Compound Elements
Carbon dioxide One carbon atom, two oxygen atoms
Sodium chloride One sodium atom, one chloride atom
Benzene Six carbon atoms, six hydrogen atoms
Ammonia One nitrogen atom, three hydrogen atom
Water One oxygen atom, two hydrogen atoms
ACTIVITY 8.2
ȱȱ
The components of a compound cannot be separated by physical methods
such as crushing or by magnetic force. Components of a compound can be
separated by chemical methods. For example, pure water can be broken
down into its elements that are oxygen and hydrogen by using electrolysis.
Compounds can be prepared by a chemical reaction. Heat energy is released
or absorbed when a compound is formed. This will form a new substance
that is different from its early substances. The characteristics of a
combination of elements which are combined by specific ratios are different
from each of the origin element. ȱ
(ii) Mixturesȱ
ȱ
ȱ Materialȱthatȱisȱmadeȱupȱofȱaȱcombinationȱofȱtwoȱorȱmoreȱsubstancesȱ
thatȱareȱcombinedȱphysicallyȱisȱcalledȱaȱmixture.ȱThisȱmeansȱthatȱtheȱ
mixtureȱ canȱ beȱ separatedȱ byȱ physicalȱ methodsȱ suchȱ asȱ filtration,ȱ
evaporation,ȱ distillation,ȱ chromatography,ȱ extraction,ȱ precipitation,ȱ
magneticȱ forces,ȱ sievingȱ andȱ heatingȱ orȱ evaporationȱ processes.ȱ Byȱ
theseȱseparationȱmethods,ȱtheȱchemicalȱstructureȱofȱtheȱcomponentȱisȱ
notȱchangedȱbecauseȱtheȱsubstanceȱinȱaȱmixtureȱdoesȱnotȱunite.ȱȱ
ȱ ȱ
ACTIVITY 8.2
Haveȱ youȱ everȱ burntȱ aȱ magnesiumȱ ribbon?ȱ Magnesiumȱ and
oxygenȱcanȱbeȱcombinedȱtoȱmakeȱaȱcompound.ȱHoldȱaȱsmallȱpiece
ofȱmagnesiumȱ ribbonȱbyȱusingȱaȱ tongȱandȱmoveȱ itȱ slowlyȱ intoȱa
flame.ȱObserveȱtheȱappearanceȱofȱmagnesiumȱandȱoxygenȱbefore
andȱafterȱitȱwasȱburnt.ȱIdentifyȱtheȱendȱproductȱofȱtheȱexperiment.ȱ
279

75
ȱ Thereȱareȱtwoȱtypesȱofȱmixtureȱ–ȱhomogenousȱandȱheterogeneous.ȱAȱ
homogenousȱ mixtureȱ isȱ formedȱ whenȱ itsȱ substancesȱ areȱ mixedȱ
evenlyȱandȱtheȱidentityȱofȱeachȱsubstanceȱcannotȱbeȱidentifiedȱeasily.ȱ
Aȱ heterogeneousȱ mixtureȱ isȱ formedȱ whenȱ itsȱ substanceȱ canȱ beȱ
identifiedȱ easily.ȱ Whenȱ sugarȱ isȱ putȱ inȱ aȱ glassȱ ofȱ hotȱ drink,ȱ itȱ
becomesȱ aȱ homogenousȱ mixture.ȱ Aȱ mixtureȱ ofȱ sulphurȱ withȱ ironȱ
fillingsȱandȱairȱareȱ examplesȱofȱaȱheterogeneousȱmixtureȱ (seeȱTableȱ
8.2).ȱ
ȱ
Tableȱ8.2:ȱSeveralȱTypesȱofȱMixturesȱ
Mixtureȱ Componentsȱ
Airȱ Oxygen,ȱnitrogen,ȱhydrogen,ȱ carbonȱdioxide,ȱ inertȱ
gases,ȱmicroorganismsȱandȱwaterȱvapourȱ
Soilȱ Water,ȱclay,ȱloam,ȱsand,ȱhumus,ȱgravelȱ
Seaȱwaterȱ Sodiumȱ chloride,ȱ water,ȱ magnesium,ȱ plumbum,ȱ
oxygenȱ
Chocolateȱ
cakeȱ
Flour,ȱwater,ȱoil,ȱegg,ȱchocolateȱpowderȱ
Bloodȱ Bloodȱ cells,ȱ hormones,ȱ minerals,ȱ water,ȱ plasma,ȱ
oxygenȱ
ȱ ȱ
ȱ Duringȱ theȱ formationȱ ofȱ aȱmixture,ȱ heatȱ energyȱ isȱ notȱ absorbedȱ orȱ
released.ȱThereȱisȱalsoȱnoȱcombinationȱofȱelementsȱinȱaȱspecificȱratioȱ
andȱeachȱcomponentȱretainsȱitsȱoriginalȱproperty.ȱTheȱcomponentsȱofȱ
aȱmixtureȱcanȱbeȱeasilyȱidentified.ȱ
SELF-CHECK 8.1
1. Whatȱisȱaȱmaterial?ȱ
2. Nameȱaȱfewȱexamplesȱofȱmaterials.ȱ
280

76
ACTIVITY 8.3
Doȱ youȱ knowȱ howȱ toȱ separateȱ gasesȱ inȱ theȱ air?ȱ Whatȱ areȱ the
proceduresȱthatȱshouldȱbeȱtakenȱtoȱturnȱitȱintoȱliquid?ȱDiscussȱwith
yourȱcoursemates.ȱ
(c) Making New Materials
Some materials around us are natural while others are man-made. Wool from
sheep and wood from trees are natural materials. All these materials are made
from elements.
Scientists sometimes combine elements in new ways. This is a way to make
useful man-made materials. Synthetic materials are an example of man-made
materials.
SELF-CHECK 8.2
Stateȱtheȱtypesȱofȱcombiningȱelements.ȱ
8.1.2 Properties of Materials
Whatȱareȱtheȱphysicalȱpropertiesȱofȱmaterials?ȱMatterȱisȱtheȱgeneralȱwordȱforȱ
allȱmaterials.ȱ Therefore,ȱ specificȱmatterȱ suchȱ asȱwood,ȱ stoneȱ andȱ paperȱ areȱ
calledȱ material.ȱ Weȱ knowȱ thatȱ materialsȱ canȱ beȱ dividedȱ intoȱ twoȱ typesȱ –ȱ
naturalȱmaterialsȱ andȱ syntheticȱmaterials.ȱNaturalȱmaterialsȱ areȱmadeȱ fromȱ
organicȱmaterialȱlikeȱpaperȱorȱinorganicȱmaterialȱlikeȱsandȱandȱlava.ȱHumansȱ
cannotȱ createȱ naturalȱmaterials.ȱHowever,ȱ scientistsȱ haveȱmanagedȱ toȱmakeȱ
syntheticȱmaterials.ȱPlasticsȱandȱceramicsȱareȱtwoȱtypesȱofȱsyntheticȱmaterials.ȱ
ȱȱȱ
Eachȱ materialȱ hasȱ itsȱ uniqueȱ physicalȱ properties,ȱ whichȱ meansȱ differentȱ
materialsȱhaveȱdifferentȱproperties.ȱSomeȱofȱtheȱimportantȱphysicalȱpropertiesȱ
ofȱ materialsȱ areȱ elasticity,ȱ shine,ȱ buoyancy,ȱ waterȱ absorbency,ȱ electricalȱ
conductivity,ȱheatȱ conductivityȱandȱmagnetism.ȱOtherȱphysicalȱpropertiesȱofȱ
materialsȱ areȱ hardness,ȱ toughnessȱ andȱ brittleness,ȱ strength,ȱ flexibility,ȱ
solubilityȱandȱwaterproof.
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Scientistsȱ distinguishȱ materialȱ propertiesȱ accordingȱ toȱ theirȱ interestingȱ
contextualȱfactors.ȱAmongȱtheseȱpropertiesȱare:ȱȱ
(a)ȱ Mechanicalȱpropertiesȱlikeȱelasticity;ȱ
(b)ȱ Thermodynamicȱpropertiesȱlikeȱspecificȱheatȱcapacityȱandȱmeltingȱpoint;ȱȱ
(c)ȱ Electromagneticȱ propertiesȱ likeȱ specificȱ magneticȱ susceptibilityȱ andȱ
specificȱelectricȱconductivity;ȱ
(d)ȱ Chemicalȱpropertiesȱlikeȱtheȱcapacityȱforȱoxidationȱorȱtheȱsolubilityȱinȱaȱ
certainȱliquid;ȱ
(e)ȱȱ Biologicalȱorȱbiochemicalȱpropertiesȱ likeȱLD50,ȱantibioticȱorȱanaestheticȱ
effect;ȱ
(f)ȱ Ecologicalȱ propertiesȱ likeȱ ozoneȱ depletionȱ potential,ȱ greenhouseȱ effectȱ
factor;ȱandȱȱ
(g)ȱ Mixedȱ materialȱ propertiesȱ (twoȱ orȱ moreȱ interestingȱ factorsȱ areȱ
combined)ȱ likeȱ photoȬchemical,ȱ thermoȬelectrical,ȱ thermoȬelectroȱ
chemical.ȱȱ
ȱ
Letȱusȱnowȱtakeȱaȱlookȱatȱtheȱtypesȱofȱmaterialȱproperties.ȱ
ȱ
(a) Elasticityȱ
ȱ
ȱ Whatȱisȱelasticity?ȱ
Elasticityȱisȱtheȱabilityȱofȱaȱmaterialȱtoȱreturnȱtoȱitsȱoriginalȱshapeȱandȱ
sizeȱafterȱbeingȱbent,ȱtwisted,ȱstretchedȱandȱsqueezed.ȱȱ
ȱ
ȱ ȱMaterialsȱ thatȱ areȱ ableȱ toȱ returnȱ toȱ theirȱ oldȱ shapeȱ whenȱ forceȱ isȱ noȱ
longerȱ appliedȱ areȱ calledȱ elasticȱ materials.ȱ However,ȱ materialsȱ whichȱ
retainȱtheirȱnewȱshapesȱwhenȱforceȱisȱnoȱlongerȱappliedȱareȱcalledȱplasticȱ
materialsȱorȱnonȬelasticȱmaterials.ȱSomeȱmaterialsȱsuchȱasȱrubberȱbands,ȱ
balloonsȱ andȱ glovesȱ areȱ elasticȱ materialsȱ butȱ someȱ materialsȱ suchȱ asȱ
plastic,ȱwoodȱ andȱbeltȱ areȱnonȬelasticȱmaterials.ȱToȱdetermineȱwhetherȱ
materialsȱ areȱ elasticȱ orȱ nonȬelastic,ȱ youȱ mayȱ needȱ toȱ carryȱ outȱ someȱ
activity.ȱȱ
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ȱ Scientistsȱ spendȱ aȱ lotȱ ofȱ theirȱ timeȱ investigatingȱ theȱ propertiesȱ ofȱ
materialsȱmainlyȱtoȱfindȱoutȱhowȱtheyȱbehaveȱinȱaȱvarietyȱofȱsituations.ȱ
Theȱmostȱ importantȱ propertyȱ isȱ howȱ aȱ particularȱmaterialȱ respondsȱ toȱ
forces.ȱWhenȱ anȱ elasticȱmaterialȱ isȱ pulled,ȱ itȱ stretchesȱ andȱ increasesȱ inȱ
length.ȱHowever,ȱtheȱincreaseȱinȱlengthȱwillȱstopȱwhenȱitȱreachesȱaȱpointȱ
whereȱ theȱmaterialȱnoȱ longerȱ returnsȱ toȱ itsȱ originalȱ shape.ȱThisȱpullȱ isȱ
alsoȱknownȱasȱtheȱelasticȱlimitȱofȱtheȱmaterial.ȱIfȱtheȱpullȱstillȱincreases,ȱ
theȱmaterialȱmayȱbreakȱdownȱ(pleaseȱreferȱtoȱFigureȱ8.3).ȱ
ȱ ȱ
ȱ
Figureȱ8.3:ȱEffectȱofȱforceȱonȱmaterialsȱ
(i) ElasticȱChangeȱ
ȱ Whenȱ enoughȱ forceȱ isȱ appliedȱ toȱ anȱ object,ȱ itȱdeforms.ȱHowever,ȱ
whenȱ theȱ forceȱ isȱ removed,ȱ theȱmaterialȱ willȱ oftenȱ returnȱ toȱ itsȱ
originalȱshape.ȱ
(ii) PlasticȱChangeȱ
ȱ Whenȱaȱlargerȱforceȱisȱapplied,ȱaȱmaterialȱmayȱcontinueȱtoȱdeform.ȱ
However,ȱwhenȱtheȱforceȱisȱremoved,ȱitȱwillȱstayȱinȱthisȱnewȱshape.ȱ
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(iii) Breakȱ
ȱ Ifȱenoughȱforceȱisȱappliedȱtoȱaȱmaterial,ȱitȱwillȱbecomeȱbrittleȱandȱ
eventuallyȱbreakȱorȱfracture.ȱ
Someȱmaterialsȱthatȱexhibitȱelasticȱbehaviourȱare:ȱ
(i) Rubber:ȱ Largeȱ deformationȱ ifȱ warm,ȱ thenȱ fractureȱ orȱ smallȱ
deformationȱandȱfractureȱifȱcold;ȱ
(ii) Metals:ȱSmallȱdeformation,ȱthenȱpermanentlyȱdeform;ȱ
(iii) Ceramics:ȱSmallȱdeformation,ȱthenȱfracture;ȱ
(iv) Electronicȱmaterials:ȱSmallȱdeformation,ȱthenȱfractureȱorȱdeform;ȱ
(v) Glass:ȱSmallȱdeformation,ȱthenȱfracture.ȱ
(vi) Humanȱskin:ȱLargeȱdeformations.ȱ
(vii) Polymers:ȱTemperatureȱdependent.ȱ
(viii) Liquidsȱunderȱuniformȱhydrostaticȱpressure.ȱȱ
ȱ
ȱ
SELF-CHECK 8.3
1. Stateȱtheȱimportanceȱofȱphysicalȱpropertiesȱofȱmaterials.
2. Giveȱanȱexampleȱofȱaȱmaterialȱforȱeachȱphysicalȱproperty.ȱ
(b)ȱ Shinyȱȱ
ȱ ȱ
ȱ Whenȱitȱcomesȱtoȱmaterialȱproperties,ȱwhatȱdoesȱshinyȱmean?ȱ
Someȱ materialsȱ areȱ shinyȱ andȱ someȱ areȱ not.ȱ Shinyȱ materialsȱ canȱ
reflectȱtheȱlightȱsuchȱasȱsomeȱtypesȱofȱmetalsȱandȱglasses.ȱȱ
ȱ
ȱ ȱShineȱisȱimportantȱinȱmakingȱjewelleryȱandȱaccessories.ȱInȱrelationȱtoȱthisȱ
shinyȱpropertyȱofȱmaterials,ȱsomeȱmaterialsȱallowȱlightȱtoȱpassȱthroughȱ
themȱbutȱsomeȱdoȱnot.ȱMaterialsȱsuchȱasȱglassȱandȱplasticȱallowȱlightȱtoȱ
passȱ throughȱ them.ȱ Onȱ theȱ otherȱ hand,ȱ materialsȱ suchȱ asȱ woodȱ andȱ
metalȱdoȱnotȱallowȱlightȱtoȱpassȱthroughȱthem.ȱAccordingȱtoȱtheȱabilityȱ
ofȱmaterialsȱ toȱ allowȱ lightȱ toȱpassȱ throughȱ them,ȱmaterialsȱ canȱ alsoȱbeȱ
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dividedȱ intoȱ threeȱ types.ȱ Thereȱ areȱ transparentȱ materials,ȱ translucentȱ
materialsȱ andȱ opaqueȱ materials.ȱ Figureȱ 8.4ȱ showsȱ objectsȱ madeȱ ofȱ
transparent,ȱtranslucentȱandȱopaqueȱmaterials.ȱ
ȱ
ȱ
Figureȱ8.4:ȱObjectsȱmadeȱofȱtransparent,ȱtranslucentȱandȱopaqueȱ
materialsȱ
ȱ
•ȱ Transparentȱmaterialsȱ
ȱ Ifȱ theȱmaterialsȱ allowȱmostȱ ofȱ theȱ lightȱ toȱ passȱ throughȱ them,ȱ itȱ isȱ
knownȱ asȱ transparentȱ materials.ȱ Examplesȱ ofȱ thisȱ typeȱ areȱ glass,ȱ
plainȱ plastic,ȱ air,ȱ water,ȱ aquariums,ȱ someȱ doorsȱ andȱ wallsȱ ofȱ
buildingsȱmadeȱ fromȱ clearȱglass.ȱWeȱ canȱ clearlyȱ seeȱ objectsȱbehindȱ
theseȱmaterials.ȱȱ
•ȱ Translucentȱmaterialsȱ
ȱ Ifȱ theȱmaterialsȱ allowȱ someȱ ofȱ theȱ lightȱ toȱpassȱ throughȱ them,ȱ itȱ isȱ
knownȱ asȱ translucentȱ materials.ȱ Objectsȱ behindȱ aȱ translucentȱ
materialȱ cannotȱbeȱ seenȱclearly.ȱ Itȱwillȱappearȱblurred.ȱExamplesȱofȱ
theseȱ materialsȱ areȱ tissueȱ paper,ȱ wrappingȱ plastic,ȱ someȱ windowȱ
panes,ȱbulbs,ȱfoodȱcontainersȱandȱsunglasses.ȱ
•ȱ Opaqueȱmaterialsȱ
ȱ Opaqueȱmaterialsȱareȱmaterialsȱwhichȱcannotȱallowȱanyȱlightȱtoȱpassȱ
throughȱ them.ȱ Weȱ cannotȱ seeȱ anythingȱ behindȱ opaqueȱ materials.ȱ
Metals,ȱ woods,ȱ rubber,ȱ bricks,ȱ roofs,ȱ walls,ȱ bags,ȱ hatsȱ andȱ paperȱ
boxesȱareȱexamplesȱofȱtheseȱmaterials.ȱ
ȱ ȱ
ȱ
ȱ
ȱ
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(c)ȱ Buoyancyȱ
ȱ ȱ
ȱ Howȱ doȱ weȱ defineȱ buoyancy?ȱ Letȱ usȱ takeȱ aȱ lookȱ atȱ theȱ followingȱ
definition.ȱ
ȱ ȱ
ȱ ȱ
Buoyancyȱisȱtheȱabilityȱofȱmaterialsȱtoȱfloatȱinȱliquid.ȱ
ȱ
ȱ Whyȱ doȱ someȱ thingsȱ float?ȱ Denseȱ objectsȱ sinkȱ andȱ lightȱ objectsȱ float.ȱ
Therefore,ȱbuoyancyȱ isȱ alsoȱ relatedȱ toȱdensity.ȱDensityȱ isȱmassȱperȱunitȱofȱ
volume.ȱȱ
ȱ ȱ
ȱ Floatingȱisȱrelatedȱtoȱtheȱvolumeȱofȱliquidȱdisplacedȱbyȱanȱobject.ȱTheȱliquidȱisȱ
pushedȱasideȱwhenȱanȱobjectȱisȱplacedȱinȱit.ȱTherefore,ȱourȱbodyȱdisplacesȱtheȱ
water.ȱWhenȱanȱobjectȱfloatsȱinȱwater,ȱonlyȱaȱpartȱofȱitȱdisplacesȱtheȱwater.ȱ
Theȱotherȱpartȱofȱtheȱobjectȱremainsȱaboveȱtheȱwater.ȱTheȱobjectsȱfloatȱafterȱaȱ
definiteȱamountȱofȱwaterȱisȱdisplaced.ȱAccordingȱtoȱArchimedes,ȱtheȱancientȱ
Greekȱphysicist,ȱwhenȱtheȱmassȱofȱtheȱdisplacedȱliquidȱisȱequalȱtoȱtheȱmassȱofȱ
theȱobjects,ȱ theȱobjectsȱwillȱ float.ȱPlastic,ȱwoodȱandȱ rubberȱareȱexamplesȱofȱ
floatingȱmaterials.ȱFigureȱ8.5ȱshowsȱfloatingȱmaterialsȱandȱliquidsȱofȱdifferentȱ
densities.ȱȱ
ȱ
ȱ
Figureȱ8.5:ȱFloatingȱmaterialsȱandȱliquidsȱofȱdifferentȱdensitiesȱ
ȱ
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(d)ȱ WaterȱAbsorbencyȱ
ȱ ȱ
ȱ Materialsȱwhichȱcanȱabsorbȱwaterȱareȱknownȱasȱabsorbentȱmaterialsȱandȱ
materialsȱ whichȱ cannotȱ absorbȱ waterȱ areȱ knownȱ asȱ nonȬabsorbentȱ
materials.ȱTheȱmaterialsȱthatȱareȱableȱtoȱabsorbȱwaterȱbecomeȱcompletelyȱ
wet.ȱExamplesȱofȱabsorbentȱmaterialsȱareȱwood,ȱpaperȱandȱcottonȱcloth.ȱ
Raincoats,ȱ umbrellas,ȱ plasticȱ andȱ hatsȱ areȱ examplesȱ ofȱ nonȬabsorbentȱ
materials.ȱ
ACTIVITY 8.4
Your friend’s child is asking you about absorbent materials. How do
you explain to your friend’s child to test absorbent and non-absorbent
materials? Discuss in pairs.
(e)ȱ ElectricalȱConductivityȱ
ȱ Aȱmaterialȱ thatȱ allowsȱ electricityȱ toȱ passȱ throughȱ itȱ isȱ aȱmaterialȱ thatȱ
conductsȱelectricity.ȱAlmostȱallȱtypesȱofȱmetalȱsuchȱasȱzinc,ȱcopper,ȱbrassȱ
andȱgoldȱareȱmaterialsȱthatȱconductȱelectricity.ȱNonȬmetalsȱsuchȱasȱglass,ȱ
wood,ȱplastic,ȱcottonȱwoolȱandȱleatherȱareȱmaterialsȱthatȱdoȱnotȱconductȱ
electricity.ȱElectricalȱconductivityȱisȱaȱmeasureȱofȱtheȱeaseȱwithȱwhichȱanȱ
electricalȱcurrentȱcanȱmoveȱinȱaȱmaterial.ȱItȱmayȱbeȱinferredȱbyȱlookingȱatȱ
theirȱ resistivity,ȱ whichȱ refersȱ toȱ itsȱ abilityȱ toȱ resistȱ theȱ passageȱ ofȱ anȱ
electricalȱcurrent.ȱFigureȱ8.6ȱshowsȱtheȱtestȱofȱelectricalȱconduction.ȱ
ȱ
ȱ
ȱ
ACTIVITY 8.4
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ȱ
Figureȱ8.6:ȱTestȱofȱelectricalȱconduction
ACTIVITY 8.5
Howȱdoȱyouȱtestȱforȱelectricalȱconduction?ȱArrangeȱequipmentȱtoȱfind
outȱwhichȱmaterialsȱ areȱ electricalȱ conductorsȱ andȱwhichȱ areȱ electrical
insulators.ȱ Figureȱ 8.6ȱ willȱ helpȱ youȱ doȱ theȱ test.ȱ Placeȱ theȱ material
betweenȱtheȱbatteryȱandȱtheȱbulbȱtoȱbeȱtested.ȱSeeȱwhatȱhappensȱtoȱthe
lightbulb.ȱ Testȱ severalȱ typesȱ ofȱ samplesȱ suchȱ asȱ pencil,ȱ flower,ȱ soil,
waterȱandȱspoon.
ȱ
Tableȱ8.3ȱsummarisesȱtheȱelectricalȱresistivityȱofȱsomeȱcommonȱmaterials.ȱ
Tableȱ8.3:ȱElectricalȱResistivityȱofȱSomeȱCommonȱMaterialsȱ
Materialsȱ ElectricalȱResistivityȱ(10Ȭ8ȱohms/m)ȱ
Copperȱ 1.67ȱ
Aluminiumȱ 2.65ȱ
Ironȱ 9.71ȱ
Steelȱ 12.0ȱ
Pyrexȱglassȱ 105ȱ
Concreteȱ 0.1ȱ
Nylonȱ 1016ȱ
Rubberȱ —ȱ
Softwoodȱ —ȱ
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(f)ȱ HeatȱConductivityȱ
ȱ ȱ
ȱ Whatȱisȱheatȱconductivity?ȱ
ȱ
ȱ ȱMetalsȱ canȱ conductȱ heatȱ whileȱ nonȬmetalsȱ cannotȱ conductȱ heat.ȱ Eachȱ
materialȱconductsȱheatȱinȱitsȱownȱspecialȱway.ȱAȱgoodȱconductorȱwouldȱ
beȱusedȱinȱradiatorsȱwhereasȱaȱpoorȱconductorȱwouldȱbeȱusedȱtoȱinsulateȱ
extremeȱheat.ȱȱ
ȱ ȱ
ȱ Scientistsȱ haveȱ aȱ wayȱ ofȱ measuringȱ theȱ valueȱ ofȱ howȱ wellȱ heatȱ isȱ
conducted.ȱIfȱtheȱvalueȱofȱaȱmaterialȱisȱlarger,ȱitȱisȱaȱbetterȱheatȱconductorȱ
comparedȱtoȱmaterialsȱwithȱsmallȱvalues.ȱTableȱ8.4ȱshowsȱtheȱvaluesȱofȱ
heatȱ conductionȱ ofȱ someȱ materials.ȱ Aȱ pieceȱ ofȱ copperȱ withȱ aȱ heatȱ
conductionȱvalueȱofȱaboutȱ8000ȱ isȱaȱbetterȱheatȱ conductorȱ thanȱ foamedȱ
plasticȱwithȱ aȱ heatȱ conductionȱ valueȱ ofȱ aboutȱ 1ȱ becauseȱ copperȱ ranksȱ
higherȱthanȱplastic.ȱ
ȱ
Tableȱ8.4:ȱValuesȱofȱHeatȱConductionȱofȱSomeȱMaterialsȱ
Materialsȱ ValuesȱofȱHeatȱConductionȱ(Relative)ȱ
Copperȱ 8000
Aluminiumȱ 4000
Brassȱ ȱ 2500
Steelȱ 1100
Pyrexȱglassȱ 24
Concreteȱ 2ȱ
Solidȱplasticȱ ȱ 6ȱ
Rubberȱ 2ȱ
FoamedȱPlasticȱ 1ȱ
ȱ
Aȱmaterialȱthatȱallowsȱheatȱtoȱpassȱthroughȱitȱeasilyȱisȱaȱmaterialȱthatȱ
conductsȱheat.ȱȱ
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(g)ȱ Magnetismȱ
ȱ ȱ
ȱ Magnetismȱisȱtheȱpropertyȱofȱmaterialsȱtoȱattractȱiron,ȱforȱexample,ȱironȱ
oxide,ȱ cobalt,ȱ nickelȱ andȱ certainȱ typesȱ ofȱ alloy.ȱ Actually,ȱ itȱ isȱ quiteȱ
difficultȱ toȱ explainȱ theȱ definitionȱ ofȱ magnetism;ȱ however,ȱ itȱ isȱ muchȱ
easierȱ toȱ explainȱ whatȱ magnetsȱ do.ȱ Someȱ ofȱ theȱ characteristicsȱ ofȱ
magnetismȱareȱasȱfollows.ȱ
(i) Magneticȱmaterialsȱcanȱbeȱattractedȱbyȱmagnets;ȱ
(ii) Attractionȱmayȱhappenȱfromȱaȱdistance;ȱ
(iii) Everyȱmagnetȱhasȱtwoȱpoles:ȱnorthȱandȱsouthȱpoles;ȱ
(iv) Differentȱpolesȱwillȱbeȱattractedȱbutȱsimilarȱpolesȱwillȱbeȱrepelled;ȱ
(v) Theȱregionȱaroundȱaȱmagnetȱisȱknownȱasȱaȱmagneticȱfield;ȱ
(vi) Bringingȱ ironȱ intoȱ closeȱ contactȱ withȱ aȱ magnetȱ willȱ produceȱ aȱ
temporaryȱmagnet;ȱ
(vii) Bringingȱ steelȱ intoȱ closeȱ contactȱ withȱ aȱ magnetȱ willȱ produceȱ aȱ
permanentȱmagnet;ȱandȱ
(viii) Magnetismȱisȱreducedȱbyȱheatingȱorȱhammeringȱaȱmagnet.ȱ
ȱ
(h)ȱ OtherȱPropertiesȱofȱMaterialsȱ
ȱ Otherȱ propertiesȱ ofȱmaterialsȱ areȱ hardness,ȱ toughnessȱ andȱ brittleness,ȱ
strength,ȱ flexibility,ȱ solubilityȱ andȱ waterproof.ȱ Tableȱ 8.5ȱ summarisesȱ
theseȱproperties.ȱ
ȱ
Tableȱ8.5:ȱOtherȱPropertiesȱofȱMaterialsȱ
Propertiesȱ Explanationȱ
Hardnessȱ Theȱ shapeȱofȱ aȱhardȱmaterialȱ isȱdifficultȱ toȱ change.ȱ Itȱwillȱ
dentȱ orȱ scratchȱ aȱ softerȱ material.ȱ Itȱ canȱ alsoȱ withstandȱ
impactȱwithoutȱchanging.ȱ
Toughnessȱ
andȱ
brittlenessȱ
Resistanceȱ toȱ breakingȱ byȱ cracking.ȱ Itȱ isȱ theȱ oppositeȱ ofȱ
brittle.ȱItȱmayȱbeȱdentedȱbyȱtheȱimpactȱbutȱitȱisȱdifficultȱtoȱ
break.ȱ
Strengthȱ Theȱ materialȱ isȱ difficultȱ toȱ breakȱ byȱ applyingȱ force.ȱ
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Materialsȱ mayȱ haveȱ tensileȱ strengthȱ andȱ compressiveȱ
strength.ȱ Tensileȱ strengthȱ meansȱ resistanceȱ toȱ stretchingȱ
suchȱasȱ squeezingȱandȱpullingȱonȱ theȱ rope.ȱ Itȱdependsȱonȱ
itsȱ crossȬsectionalȱ area.ȱ Compressiveȱ strengthȱ meansȱ
resistanceȱ toȱ pressure,ȱ meaningȱ itȱ isȱ hardȱ toȱ breakȱ byȱ
crushing.ȱ
Flexibilityȱ Theȱmaterial,ȱwhichȱisȱeasyȱtoȱbendȱwithoutȱbreaking,ȱhasȱ
bothȱtensileȱstrengthȱandȱcompressiveȱstrength.ȱ
Solubilityȱ Theȱ solubilityȱ isȱ theȱ concentrationȱofȱ soluteȱ inȱ aȱ saturatedȱ
solution.ȱItȱisȱstatedȱasȱtheȱmassȱinȱgramsȱofȱtheȱsoluteȱthatȱ
willȱsaturateȱ100ȱgramsȱofȱsolventȱatȱaȱcertainȱtemperature.ȱ
Waterproofȱ Resistanceȱtoȱliquids.ȱRepelsȱwater.ȱ
ȱ ȱ
ȱȱȱȱȱȱȱȱȱ
ACTIVITY 8.6
ȱGoȱ onȱ theȱ Internetȱ andȱ findȱ outȱmoreȱ onȱmaterialsȱ andȱ theirȱ uses
basedȱ onȱ theirȱ properties.ȱ Discussȱ yourȱ findingsȱ withȱ you
coursemates.ȱ
ȱ
8.1.3 Importance of Materials
ȱ
Materialsȱ playȱ aȱ pivotalȱ roleȱ inȱ ourȱ life,ȱ particularlyȱ inȱ theȱ areasȱ ofȱ livingȱ
environment,ȱhealth,ȱcommunication,ȱconsumerȱgoodsȱandȱtransport.ȱPressingȱ
environmentalȱconcernsȱforceȱusȱtoȱuseȱmaterialsȱmoreȱefficiently.ȱItȱwillȱhelpȱ
inȱ theȱ longȱ runȱ ifȱ weȱ developȱ newȱ energyȱ generationȱ technologies,ȱ moreȱ
energyȱ efficientȱdevices,ȱ andȱ easilyȱ recyclable,ȱ lessȱ toxicȱmaterials.ȱAsȱ farȱ asȱ
consumerȱ goodsȱ areȱ concerned,ȱ weȱ needȱ toȱ emphasiseȱ notȱ onlyȱ onȱ theȱ
materialȱ productsȱ butȱ alsoȱ onȱ theȱwayȱ theyȱ areȱ handledȱ suchȱ asȱpackaging,ȱ
fasterȱproductionȱandȱhigherȱqualityȱgoods.ȱ
ȱ ȱ
Inȱ health,ȱmaterialsȱ areȱ importantȱ toȱ helpȱusȱ overcomeȱdiseaseȱ andȱprovideȱ
worldwideȱ medicalȱ care.ȱ Inȱ transport,ȱ weȱ needȱ durable,ȱ highȬperformanceȱ
materialsȱ thatȱ makeȱ travellingȱ faster,ȱ saferȱ andȱ moreȱ comfortable.ȱ Inȱ
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communication,ȱ theȱ developmentȱ ofȱ newȱ electronicȱ inventionsȱ isȱ veryȱ
importantȱandȱrequiresȱopticalȱandȱmagneticȱmaterials.ȱWithoutȱdevelopmentȱ
ofȱmaterialsȱinȱallȱareas,ȱweȱmayȱfaceȱmanyȱdifficulties.ȱ
(a) ImportanceȱofȱPhysicalȱPropertiesȱofȱMaterialsȱȱ
Knowledgeȱaboutȱtheȱpropertiesȱofȱmaterialsȱisȱveryȱimportant,ȱespeciallyȱ
inȱ choosingȱ suitableȱmaterialsȱ toȱmakeȱ variousȱ objects.ȱ Sometimesȱ theseȱ
objectsȱ needȱmoreȱ thanȱ oneȱ typeȱ ofȱ physicalȱ property.ȱ Forȱ thousandsȱ ofȱ
years,ȱpeopleȱonlyȱusedȱnaturalȱpropertiesȱofȱnaturalȱmaterials.ȱHowever,ȱ
scientistsȱ haveȱ nowȱ developedȱ manyȱ newȱ materials,ȱ influencingȱ itsȱ
propertiesȱinȱtheȱprocess.ȱ
(b) UseȱofȱPropertiesȱofȱMaterialsȱinȱEverydayȱLifeȱ
Humansȱhaveȱexploitedȱphysicalȱpropertiesȱofȱmaterialsȱforȱtheirȱownȱuseȱ
inȱ everydayȱ life.ȱ Weȱ useȱ materialsȱ thatȱ conductȱ electricityȱ toȱ produceȱ
conductorsȱ andȱ insulators.ȱ Weȱ useȱ materialsȱ thatȱ allowȱ lightȱ toȱ passȱ
throughȱ themȱ toȱ produceȱ transparent,ȱ translucentȱ andȱ opaqueȱ objects.ȱ
Tableȱ 8.6ȱ showsȱotherȱusesȱofȱpropertiesȱofȱmaterialsȱ inȱproducingȱ someȱ
everydayȱobjects.ȱ
ȱ
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Tableȱ8.6:ȱOtherȱUsesȱofȱPropertiesȱofȱMaterialsȱinȱProducingȱSomeȱEverydayȱ
Objectsȱ
Propertyȱ Materialsȱ Usesȱ
Strengthȱ
Metalsȱ
ȱ
Structuralȱcomponentsȱ
E.g.,ȱrolledȱsteelȱjointsȱ
Malleabilityȱ Waterȱpipesȱ
Thermalȱ
conductivityȱ
Radiators,ȱsaucepans,ȱovensȱ
Electricalȱ
conductivityȱ
Electricalȱcablesȱ
Hardnessȱ Drillȱbits,ȱhammerheadsȱ
Strengthȱ
Ceramicsȱ
Brick,ȱconcreteȱ
Heatȱresistanceȱ Ovenwareȱ
Abrasionȱ
Crockeryȱ
resistanceȱ
Thermalȱ
insulationȱ
Glassȱ Loft,ȱcavityȱwallȱinsulationȱ
Transparencyȱ Windowsȱ
Flexibilityȱ
Plasticsȱ
Mouldedȱitemsȱ
Electricalȱ
insulationȱ
Sheathingȱofȱelectricalȱcablesȱ
Thermalȱ
insulationȱ
Saucepanȱhandlesȱ
Lightnessȱ andȱ
strengthȱ
Construction,ȱwindowȱframesȱ
Lightnessȱ andȱ
strengthȱ Woodȱ
Construction,ȱ doors,ȱ windowȱ
frames,ȱȱ
furnitureȱȱ ȱ
Flexibility,ȱ
insulationȱ Fabricsȱ Curtains,ȱclothing,ȱfurnishingȱ
Adaptedȱ from:ȱ Farrow,ȱ S.ȱ (1996).ȱ Theȱ reallyȱ usefulȱ scienceȱ book:ȱ Aȱ
frameworkȱofȱknowledgeȱforȱprimaryȱteachers.ȱLondon:ȱFalmerȱPress.ȱ
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8.2
ȱ NATURAL MATERIALS
AllȱlivingȱthingsȱandȱnonȬlivingȱthingsȱareȱsourcesȱofȱmaterials.ȱMaterialsȱthatȱ
areȱoriginatedȱfromȱnatureȱ suchȱ asȱ livingȱorganisms,ȱplantsȱ andȱ animalsȱ areȱ
classifiedȱasȱbioticȱorȱbiologicalȱderivedȱnaturalȱmaterial.ȱMaterialsȱoriginatedȱ
fromȱ soil,ȱ petroleumȱ orȱ metalsȱ areȱ classifiedȱ asȱ abioticȱ orȱ nonȬbiologicalȱ
naturalȱmaterials.ȱWeȱneedȱtheseȱmaterialsȱtoȱsupportȱourȱdailyȱneeds.ȱȱ
ȱ
Naturalȱmaterialsȱareȱmadeȱnaturallyȱafterȱaȱlongȱperiodȱofȱtime.ȱForȱexample,ȱ
aȱ rubberȱ treeȱmayȱ takeȱmanyȱyearsȱ toȱbecomeȱmatureȱ andȱ readyȱ forȱ cuttingȱ
downȱtoȱmakeȱfurniture,ȱpapersȱandȱinsulators.ȱChemistryȱhasȱenabledȱusȱtoȱ
synthesiseȱnewȱmaterials,ȱwhichȱhaveȱdesiredȱproperties,ȱ thusȱmakingȱ themȱ
evenȱbetterȱthanȱnaturalȱmaterialsȱinȱaȱshorterȱperiodȱofȱtime.ȱȱ
ȱ
(a)ȱ IdentifyingȱNaturalȱMaterialsȱ
ȱ Materialsȱ thatȱ areȱ classifiedȱ asȱ naturalȱ materialsȱ originatedȱ fromȱ soil,ȱ
rocks,ȱwater,ȱplants,ȱanimalsȱorȱminerals.ȱAirȱisȱaȱmixtureȱofȱgases,ȱwhichȱ
makeȱupȱtheȱearth’sȱatmosphereȱandȱhasȱanȱabundanceȱofȱcomponents.ȱ
PartsȱofȱtheirȱusesȱcanȱbeȱseenȱinȱTableȱ8.7.ȱ
ȱ
Tableȱ8.7:ȱGasesȱandȱTheirȱUsesȱ
Gasȱ %ȱPresentȱ
inȱAirȱ
Usesȱ
Nitrogenȱ 78.0ȱ Nitratesȱinȱsoil,ȱuseȱinȱammoniaȱproduction.ȱȱ
Oxygenȱ 21.0ȱ Respiration,ȱoxidation,ȱmedicalȱapplicationȱ
Carbonȱdioxideȱ 0.04ȱ Photosynthesis,ȱdryȱiceȱ
Neonȱ Traceȱ Lightingȱ
Argonȱ Traceȱ Domesticȱlightȱbulbȱ
Heliumȱ Traceȱ Airshipsȱ
Kryptonȱ Traceȱ Highȱtemperatureȱlightȱbulbȱ
Xenonȱ Traceȱ Highȱtemperatureȱlightȱbulbȱ
ȱ ȱ
ȱ
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ȱ Waterȱisȱaȱcolourless,ȱodourlessȱliquid,ȱwhichȱisȱoriginallyȱderivedȱfromȱ
theȱearth’sȱatmosphere.ȱItȱisȱrecycledȱfromȱtheȱatmosphereȱtoȱtheȱcrustȱofȱ
theȱearth.ȱItȱisȱimportantȱbecauseȱitȱsupportsȱlifeȱonȱtheȱplanet,ȱasȱalmostȱ
allȱ theȱ significantȱ reactionsȱ atȱ cellularȱ levelȱ dependȱ onȱ theȱ aqueousȱ
solutions.ȱ
ȱ ȱ
ȱ Wood,ȱmetal,ȱleather,ȱcotton,ȱrubberȱandȱsilkȱareȱmaterialsȱthatȱareȱmadeȱ
ofȱ naturalȱ materials.ȱ Theseȱ materialsȱ areȱ consideredȱ valuableȱ inȱ theirȱ
relativelyȱunmodifiedȱ(natural)ȱform.ȱȱ
ȱ ȱ
(b)ȱ ObjectsȱfromȱNaturalȱMaterialsȱ
ȱ Materialsȱ fromȱ naturalȱ materialsȱ varyȱ inȱ theirȱ use.ȱ Tableȱ 8.8ȱ showsȱ
naturalȱmaterialsȱandȱtheirȱuses.ȱ
Tableȱ8.8:ȱNaturalȱMaterialsȱandȱTheirȱUsesȱ
NaturalȱMaterialȱ Usesȱ
Rubberȱ Latexȱ
Woodȱ Timberȱ
Paraffinȱwaxȱandȱstearicȱacidȱ Candlesȱ
Carbonȱblackȱandȱwaterȱorȱoilȱ Inkȱ
Vegetableȱfibreȱ Woodȱpulpȱ
Vegetableȱwaxes,ȱoilȱandȱsapȱ Carnaubaȱwax,ȱlinseedȱoilȱ
Animalȱfibreȱ Wool,ȱalpacaȱ
Animalȱproductȱ Leatherȱ,ȱtallow,ȱlardȱ
ȱ ȱ
(c)ȱ SourceȱofȱRawȱMaterialsȱ
ȱ Rawȱmaterialsȱareȱmaterialsȱthatȱareȱextractedȱfromȱtheȱearth.ȱProcessedȱ
rawȱmaterialsȱareȱcalledȱ”semiȬfinishedȱmaterials”.ȱWhenȱitȱisȱtransferredȱ
intoȱaȱnewȱcycleȱofȱproduction,ȱtheȱendȱproductȱisȱreadyȱforȱuse.ȱ
ȱ ȱ
ȱ Theȱearthȱisȱtheȱmainȱsourceȱofȱrawȱmaterials.ȱBioticȱmaterialsȱandȱnonȬ
bioticȱmaterialsȱareȱtheȱtypesȱofȱsourcesȱofȱrawȱmaterials.ȱWood,ȱstraw,ȱ
humus,ȱ spiderȱ silk,ȱ andȱ boneȱ areȱ examplesȱ ofȱ bioticȱ materials.ȱ Bioticȱ
materialsȱ areȱ usuallyȱ biodegradable,ȱ renewableȱ andȱ processingȱ hasȱ
minimalȱ impactȱ onȱ theȱ environment.ȱ Somehow,ȱ inȱ certainȱ cases,ȱ
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processingȱ producesȱ carbonȱ emission.ȱ Polylacticȱ acid,ȱ cornstarchȱ andȱ
bioplasticȱ areȱ examplesȱ ofȱ nonȬbiodegradableȱ bioticȱ materials.ȱ NonȬ
bioticȱ materialsȱ areȱ materialsȱ thatȱ doȱ notȱ originateȱ fromȱ plantsȱ andȱ
animals.ȱ Water,ȱ soil,ȱ coal,ȱ crudeȱ oil,ȱ naturalȱ gas,ȱ rocksȱ andȱ airȱ areȱ
examplesȱofȱnonȬbioticȱrawȱmaterials.ȱ
ȱ
Anotherȱexampleȱisȱcotton.ȱCottonȱisȱproducedȱfromȱaȱmaturedȱflowerȱofȱ
aȱ cottonȱ tree.ȱ Itȱ isȱ harvestedȱ byȱ pluckingȱ fromȱ aȱmaturedȱ cottonȱ treeȱ
flower.ȱ Theȱ fluffyȱ whiteȱ materialȱ isȱ thenȱ broughtȱ toȱ theȱ factoryȱ andȱ
processedȱtoȱproduceȱcottonȱthread.ȱ
ȱ
ȱ
1. Whatȱisȱaȱnaturalȱmaterial?ȱ
2. Stateȱsomeȱobjectsȱthatȱareȱmadeȱfromȱnaturalȱmaterials.ȱ
3. Giveȱasȱmanyȱexamplesȱasȱyouȱcanȱofȱrawȱmaterialsȱthatȱcanȱbeȱfound
ȱ
SELF-CHECK 8.3
inȱyourȱsurroundings.ȱ
MANUFACTURED MATERIALS
8.3
Manufacturedȱ materialsȱ areȱ madeȱ fromȱ aȱ mixtureȱ ofȱ naturalȱ materialsȱ
throughȱ chemicalȱ processes.ȱ Theseȱ materialsȱ areȱ alsoȱ calledȱ manȬmadeȱ
materials.ȱTheseȱmaterialsȱareȱprocessedȱinȱfactoriesȱwithȱaȱcombinationȱofȱaȱ
fewȱdifferentȱtypesȱofȱmaterialsȱorȱfromȱoneȱtypeȱofȱnaturalȱmaterial.ȱ
ȱ
(a)ȱ IdentifyingȱManufacturedȱMaterialsȱ
ȱ Basicȱ manufacturingȱ processesȱ frequentlyȱ usedȱ inȱ theȱ productionȱ ofȱ
manufacturedȱ materialsȱ areȱ relativelyȱ simple,ȱ oftenȱ involvingȱ
irreversibleȱchemicalȱreactions.ȱTheseȱreactionsȱareȱimportantȱinȱorderȱtoȱ
provideȱ furtherȱ rawȱ materialsȱ forȱ moreȱ complicatedȱ secondaryȱ
processes.ȱȱ
ȱ ȱ
ȱ Theȱ physicalȱ processȱ ofȱ rawȱ materialsȱ wouldȱ includeȱ theȱ refiningȱ ofȱ
metalsȱ fromȱ ores,ȱ theȱ firingȱ ofȱ ceramicȱ fromȱ claysȱ andȱ theȱmakingȱ ofȱ
glassȱfromȱsandȱandȱminerals.ȱ
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ȱȱ Theȱsawingȱofȱtimber,ȱtheȱproductionȱofȱpaperȱfromȱwoodȱpulpȱandȱtheȱ
productionȱ ofȱ latexȱ fromȱ rubberȱ areȱ examplesȱ ofȱ basicȱmanufacturingȱ
processesȱ thatȱ involveȱ biologicalȱ rawȱ materials.ȱ Secondaryȱ industriesȱ
involveȱ theȱ productionȱ ofȱ plasticsȱ (includingȱ syntheticȱ fibresȱ suchȱ asȱ
nylonȱ andȱ terylene)ȱ fromȱ crudeȱ oilȱ derivatives,ȱ detergents,ȱ paintȱ andȱ
perfumeȱfromȱcoal,ȱandȱothers.ȱ
ȱ
ȱ Manufacturedȱmaterialsȱusuallyȱhaveȱbetterȱpropertiesȱcomparedȱtoȱtheȱ
naturalȱmaterialsȱfromȱwhichȱtheyȱcomeȱfrom.ȱTheyȱareȱusuallyȱdesignedȱ
forȱspecificȱneeds,ȱlikeȱtyresȱareȱmadeȱofȱlatexȱandȱsulphur.ȱMetals,ȱglass,ȱ
ceramics,ȱplasticsȱ(includingȱrubber),ȱpaperȱandȱfabricsȱareȱexamplesȱofȱ
manufacturedȱmaterials.ȱ
ACTIVITY 8.7
Searchȱ theȱ Internetȱ forȱ manufacturedȱ materials.ȱ Findȱ outȱ the
propertiesȱofȱmanufacturedȱmaterials.ȱ
ȱȱȱȱȱ ȱ
ȱ
(b)ȱ ObjectsȱfromȱManufacturedȱMaterialsȱ
ȱ
ȱ Tableȱ 8.9ȱ listsȱ aȱ fewȱ examplesȱ ofȱ objectsȱ fromȱmanufacturedȱmaterialsȱ
andȱtheirȱuses.ȱYouȱcanȱlistȱyourȱownȱexamplesȱthatȱareȱusedȱinȱourȱdailyȱ
life.ȱ
ȱ
Tableȱ8.9:ȱObjectsȱfromȱManufacturedȱMaterialsȱ
Manufacturedȱ
Materialȱ
Syntheticȱ
Polymerȱ Usesȱ
Syntheticȱ
rubberȱ
StyreneȬbutadieneȱ
rubberȱ(SBR)ȱ Tyres,ȱshoeȱsolesȱ
Neopreneȱrubberȱ Waterȱpipes,ȱhandȱglovesȱ
Butylȱrubberȱ Tyres,ȱshoeȱsoles,ȱhosesȱ
Metalsȱ
Stainlessȱsteelȱ Cookingȱutensil,ȱȱ
Bronzeȱ Medals,ȱ
Duraluminȱ Cookingȱutensilȱ
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Glassȱ
Pyrexȱ Laboratoryȱ apparatus,ȱ cookingȱ
utensilȱ
Crystalȱ Cookingȱutensilȱ
Ceramicȱ
Brickȱ Buildingȱ
Tilesȱ Buildingȱ
Potteryȱ Decorationȱ
Fabricȱ Nylonȱ Clothȱ
Plasticȱ
Polyvinylȱchlorideȱ Electricalȱ insulators,ȱ musicȱ records,ȱ
pipes,ȱbottlesȱ
Nylonȱ Syntheticȱtextile,ȱstring,ȱparachutesȱ
Polytheneȱ Plasticȱbags,ȱfoodȱcontainers,ȱpailsȱ
Polystyreneȱ Packagingȱmaterials,ȱheatȱinsulators,ȱ
toysȱ
Melamineȱ Plates,ȱcupsȱ
Epoxyȱglueȱ Glue,ȱelectricalȱinsulatorsȱ
ȱ ȱ
ȱ
ȱ
ȱ
ȱ ȱ
ȱ
ȱ
ȱ
ȱ
SELF-CHECK 8.4
1. Explainȱwhatȱmanufacturedȱmaterialsȱare.ȱ
2. Stateȱ theȱ processesȱ thatȱ areȱ appliedȱ toȱ produceȱ manufactured
materialsȱ.ȱȱȱ
3. Giveȱexamplesȱofȱobjectsȱfromȱmanufacturedȱmaterials.
ACTIVITY 8.8
Youȱ areȱ givenȱ aȱ sampleȱ ofȱ twoȱ materials.ȱ Oneȱ isȱ aȱ natural
materialȱ andȱ theȱotherȱoneȱ isȱ aȱmanufacturedȱmaterial.ȱ Inȱyour
group,ȱ planȱ anȱ investigationȱ toȱ compareȱ theȱ materialsȱ by
choosingȱaȱsuitableȱcharacteristic.ȱMakeȱaȱprediction.ȱThenȱplanȱa
fairȱtest.ȱ
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PRESERVATION OF NATURAL
MATERIALS
8.4
ȱ ȱ
Aboutȱaȱcenturyȱago,ȱalmostȱtheȱentireȱcountryȱwasȱcoveredȱwithȱforests.ȱWildȱ
cuttingȱofȱforestsȱduringȱtheȱearlyȱsettlementȱcausedȱvastȱareasȱofȱbaredȱland.ȱ
Thisȱ phenomenonȱ ofȱ cuttingȱ downȱ plantsȱ forȱ timberȱ andȱ developmentȱ
continuesȱtoday.ȱ
ȱ
Preservationȱrefersȱtoȱtheȱeffortȱtoȱmaintainȱnaturalȱresourcesȱinȱtheirȱoriginalȱ
stateȱorȱinȱgoodȱcondition.ȱGenerally,ȱpreservationȱisȱrelatedȱtoȱconservation.ȱ
Conservationȱ refersȱ toȱ theȱ sustainableȱ useȱ andȱ managementȱ ofȱ naturalȱ
materialsȱtoȱpreventȱloss,ȱwastageȱorȱdamage.ȱ
ȱ
Theȱ importanceȱ ofȱ preservationȱ isȱ toȱ ensureȱ aȱ continuousȱ supplyȱ ofȱ naturalȱ
resources,ȱ reduceȱ environmentalȱ pollution,ȱ maintainȱ balanceȱ inȱ nature,ȱ
preventȱextinctionȱofȱ livingȱorganisms,ȱpreventȱ lossȱofȱhabitatsȱandȱkeepȱ theȱ
environmentȱcleanȱandȱconduciveȱforȱhealthyȱliving.ȱȱ
ȱ
Preservationȱshouldȱbeȱpractised.ȱSomeȱofȱtheȱactionsȱthatȱshouldȱbeȱtakenȱtoȱ
preserveȱnaturalȱmaterialsȱare:ȱ
ȱ
(a)ȱ PreventingȱForestȱFiresȱ
ȱ Forestȱfiresȱareȱwildlyȱdestructive.ȱPlantsȱandȱwildlifeȱareȱkilled.ȱForestȱ
firesȱ areȱ causedȱ byȱ lightningȱ (naturalȱ cause)ȱ andȱ people’sȱ carelessnessȱ
(accidentalȱcause).ȱ
ȱ ȱ
(b)ȱ ImprovementȱCuttingȱ
ȱ Unwantedȱtreesȱinȱaȱforestȱareȱremovedȱfromȱtheȱstand.ȱCrooked,ȱagedȱ
andȱdiseasedȱtreesȱasȱwellȱasȱtreesȱofȱlessȱdesirableȱspeciesȱareȱcut.ȱInȱthisȱ
way,ȱ spaceȱ isȱ providedȱ forȱ theȱgrowthȱofȱhealthy,ȱmoreȱvaluableȱ trees.ȱ
Thisȱpracticeȱincreasesȱlumberȱyieldȱandȱimprovesȱitsȱquality.ȱ
ȱ ȱ
(c)ȱ EnforcementȱofȱLawsȱandȱRegulationȱ
ȱ Thisȱactionȱisȱtakenȱtoȱprotectȱendangeredȱspeciesȱandȱtoȱpreventȱthemȱ
fromȱ becomingȱ extinct.ȱ Examplesȱ ofȱ protectedȱ endangeredȱ speciesȱ areȱ
theȱMalayanȱ tiger,ȱ Sumatranȱ rhinoceros,ȱ leatherbackȱ turtle,ȱ orangȱutanȱ
(seeȱFigureȱ8.7)ȱandȱdeer.ȱ
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ȱ
ȱ
Figureȱ8.7:ȱTheȱgovernmentȱtodayȱhasȱenforcedȱlawsȱandȱregulationȱtoȱprotectȱ
theȱorangȱutanȱandȱtheirȱhabitatȱ
ȱ
ȱ
ȱ
ȱ
ȱ
SELF-CHECK 8.5
Whatȱactionsȱshouldȱweȱtakeȱtoȱpreserveȱourȱnaturalȱmaterials?ȱ
ACTIVITY 8.9
1.ȱ Whatȱnaturalȱresourcesȱareȱdestroyedȱbyȱforestȱfire?ȱ
2.ȱ Inȱ aȱgroup,ȱdiscussȱwhatȱ actionȱ shouldȱbeȱ takenȱ toȱpreventȱ forest
fire.ȱ
COMPOSITE MATERIALS
8.5
Compositeȱmaterialsȱ areȱ thoseȱ thatȱ combineȱ theȱ propertiesȱ ofȱ twoȱ orȱmoreȱ
constituentsȱ inȱ orderȱ toȱ getȱ theȱ exactȱpropertiesȱ neededȱ forȱ aȱparticularȱ job.ȱ
Theȱ examplesȱ ofȱ materialȱ usuallyȱ usedȱ areȱ metals,ȱ alloys,ȱ glass,ȱ ceramics,ȱ
plasticsȱandȱpolymers.ȱȱAȱcompositeȱmaterialȱhasȱpropertiesȱthatȱareȱsuperiorȱ
toȱthoseȱofȱtheȱoriginalȱcomponents.ȱ
ȱ
Thereȱareȱmanyȱexamplesȱofȱcompositesȱinȱnature.ȱȱAȱtreeȱcanȱgrowȱtoȱgreatȱ
heightsȱ andȱ supportȱ heavyȱ branchesȱ becauseȱ itȱ isȱ aȱ compositeȱ ofȱ flexibleȱ
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celluloseȱfibresȱinȱaȱligninȱmatrixȱ(seeȱFigureȱ8.8).ȱSeashellsȱandȱlimestoneȱareȱ
bothȱmadeȱofȱcalciumȱcarbonate,ȱbutȱseashellsȱareȱmuchȱharderȱbecauseȱtheyȱ
areȱ compositesȱ ofȱ crystallineȱ calciumȱ carbonateȱwithȱ embeddedȱpolypeptideȱ
fibres.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.8:ȱTheȱcombinationȱofȱcelluloseȱfibresȱandȱligninȱmakeȱtheȱcellȱwallȱ
strongȱ
ȱ
Theȱcompositeȱindustryȱwasȱlaunchedȱinȱtheȱearlyȱ1960sȱwithȱtheȱdevelopmentȱ
ofȱfibreglassȱorȱglassȬreinforcedȱplastic.ȱItȱisȱmadeȱbyȱembeddingȱshortȱfibresȱ
ofȱglassȱinȱaȱmatrixȱofȱplastic.ȱTheȱglassȱfibresȱgiveȱtheȱplasticȱextraȱstrengthȱsoȱ
thatȱ itȱ doesȱ notȱ breakȱwhenȱ itȱ isȱ bentȱ orȱmouldedȱ intoȱ shape.ȱ Theȱ finishedȱ
productȱhasȱtheȱlightnessȱofȱplasticȱasȱwellȱasȱtheȱstrengthȱandȱflexibilityȱofȱtheȱ
glassȱ fibres.ȱTheyȱhaveȱ foundȱ inȱmanyȱmarine,ȱhousing,ȱ construction,ȱ sportsȱ
andȱ industrialȱ applications.ȱ Figureȱ 8.9ȱ showsȱ theȱ useȱ ofȱ glassȬreinforcedȱ
plasticȱinȱmakingȱtheȱbodyȱofȱtheȱboat.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱȱ
ȱ
ȱ
ȱ
Figureȱ8.9:ȱTheȱglassȬreinforcedȱplasticȱusedȱtoȱmakeȱboatsȱ
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Anotherȱcompositeȱmaterialȱwhichȱisȱusuallyȱusedȱforȱtheȱconstructionȱofȱlargeȱ
structuresȱ likeȱ highȬriseȱ buildings,ȱ bridgesȱ andȱ oilȱ platformsȱ areȱ reinforcedȱ
concreteȱ(seeȱFigureȱ8.10).ȱConcreteȱisȱaȱcompositeȱmaterialȱthatȱconsistsȱofȱaȱ
mixtureȱofȱstones,ȱchipsȱandȱsandȱboundȱtogetherȱbyȱcement.ȱItȱisȱstrongȱbutȱ
brittleȱandȱweakȱinȱtensileȱstrength.ȱToȱovercomeȱthisȱweakness,ȱtheȱconcreteȱ
canȱbeȱreinforcedȱwithȱsteelȱwireȱnettingȱorȱsteelȱrod,ȱwhichȱresultsȱtoȱaȱveryȱ
toughȱ materialȱ withȱ highȱ tensileȱ strength.ȱ Reinforcedȱ concreteȱ isȱ relativelyȱ
cheapȱandȱcanȱbeȱmouldedȱintoȱanyȱshape.ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.10:ȱTheȱreinforcedȱconcreteȱwithȱsteelȱwireȱnettingȱandȱsteelȱrodsȱ
ȱ
Theȱstrongestȱnewȱcompositeȱareȱtheȱadvancedȱcomposites,ȱinȱwhichȱfibresȱareȱ
alignedȱorȱinterwovenȱbeforeȱbeingȱsetȱwithinȱtheȱresin.ȱAdvancedȱcompositesȱ
haveȱ extraordinaryȱ strengthȱ inȱ theȱ directionȱ ofȱ theȱ alignedȱ fibresȱ andȱ areȱ
relativelyȱweakȱinȱtheȱperpendicularȱdirection.ȱWeaknessȱinȱoneȱdirectionȱcanȱ
beȱovercomeȱbyȱlaminatingȱlayersȱtogetherȱatȱdifferentȱangles,ȱasȱinȱplywood,ȱ
aȱfamiliarȱcomposite.ȱStrengthȱinȱallȱdirectionsȱcanȱbeȱachievedȱbyȱweavingȱtheȱ
fibresȱ intoȱ aȱ threeȬdimensionalȱ network.ȱ Besidesȱ strength,ȱ advancedȱ
compositesȱareȱalsoȱknownȱforȱtheirȱlightness,ȱwhichȱmakeȱthemȱidealȱforȱcarȱ
parts,ȱ sportingȱ goodsȱ andȱ artificialȱ limbs.ȱ Advancedȱ compositesȱ tendȱ toȱ beȱ
expensive,ȱhoweverȱbecauseȱmuchȱofȱ theirȱproductionȱ isȱ stillȱdoneȱbyȱhand.ȱ
Aeroplaneȱparts,ȱandȱevenȱwholeȱaeroplane,ȱareȱnowȱbeingȱfabricatedȱoutȱofȱ
lightweightȱadvancedȱcompositesȱinȱorderȱtoȱsaveȱfuel.ȱȱInȱ1986,ȱtheȱfirstȱplaneȱ
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builtȱ withȱ allȱ advancedȱ compositesȱ materialȱ isȱ ”Voyager”,ȱ whichȱ canȱ flyȱ
aroundȱtheȱworldȱwithoutȱrefuellingȱ(seeȱFigureȱ8.11).ȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.11:ȱTheȱallȬadvancedȱcompositeȱ”Voyager”ȱaeroplaneȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ACTIVITY 8.10
1. What is a composite and what are some examples found in nature other
than given in the text?
2. Where are you most likely to find composites in the marketplace today?
3. Why are composites an ideal material for aircraft?
MATERIALS IN INDUSTRY
8.6
Letȱusȱnowȱlearnȱonȱtheȱmaterialsȱinȱindustry.ȱ
8.6.1 Soap
ȱ
Millionsȱ ofȱ tonnesȱ ofȱ soapsȱ areȱ manufacturedȱ worldwideȱ everyȱ yearȱ (seeȱ
Figureȱ 8.12).ȱ Soapȱ isȱmanufacturedȱbyȱheatingȱnaturalȱ fatsȱ andȱoilsȱofȱ eitherȱ
plantsȱorȱanimalsȱwithȱaȱstrongȱalkali.ȱTheseȱfatsȱandȱoils,ȱcalledȱtriglycerides,ȱ
areȱ complicatedȱ esterȱ molecules.ȱ Pioneersȱ preparedȱ theirȱ soapȱ byȱ boilingȱ
animalȱfatȱwithȱanȱalkalineȱsolutionȱobtainedȱfromȱtheȱashesȱofȱhardwood.ȱTheȱ
resultingȱ“lye”ȱsoapȱcouldȱbeȱ“salted”ȱoutȱbyȱaddingȱsodiumȱchoride,ȱbecauseȱ
soapȱisȱlessȱsolubleȱinȱaȱsaltȱsolutionȱthanȱinȱwater.ȱ
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Figureȱ8.12:ȱSoapȱisȱmanufacturedȱbyȱheatingȱnaturalȱfatsȱandȱoilȱwithȱaȱstrongȱ
alkaliȱ
ȱ
Nowadays,ȱ fatȱ isȱ boiledȱwithȱ aqueousȱ sodiumȱ hydroxideȱ toȱ formȱ soap.ȱTheȱ
estersȱ areȱ brokenȱ downȱ inȱ theȱ presenceȱ ofȱ waterȬhydrolysed.ȱ Thisȱ typeȱ ofȱ
reactionȱ isȱ calledȱ saponification.ȱ Theȱ equationȱ givenȱ belowȱ isȱ thatȱ forȱ theȱ
saponificationȱofȱglycerylȱstearateȱ(aȱfat)ȱ(seeȱFigureȱ8.13).ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.13:ȱSaponificationȱreactionȱ
ȱ
glyceryl stearate + sodium hydroxide Æ sodium stearate + glycerol
(soap)
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Theȱ cleaningȱ propertiesȱ ofȱ theȱ soapȱ dependȱ onȱ itsȱ structureȱ andȱ bonding.ȱȱ
Sodiumȱ stearateȱ consistsȱ ofȱ aȱ longȱhydrocarbonȱ chainȱwhichȱ isȱhydrophobicȱ
(waterȱhating)ȱattachedȱtoȱanȱionicȱ”head”ȱwhichȱisȱhydrophilicȱ(waterȱloving)ȱ
(seeȱFigureȱ8.14).ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.14:ȱSimplifiedȱdiagramȱofȱaȱsoapȱmoleculeȱ
ȱ
Covalentȱ compoundsȱ areȱ generallyȱ insolubleȱ inȱ waterȱ butȱ theyȱ areȱ moreȱ
solubleȱinȱorganicȱsolvents.ȱȱIonicȱcompoundsȱareȱgenerallyȱwaterȱsolubleȱbutȱ
tendȱtoȱbeȱinsolubleȱinȱorganicȱsolvents.ȱȱWhenȱsoapȱisȱputȱintoȱwaterȱwhichȱ
hasȱaȱgreasyȱdishȱ(orȱaȱgreasyȱcloth)ȱinȱit,ȱtheȱhydrophobicȱhydrocarbonȱchainȱ
onȱeachȱsoapȱmoleculeȱbecomeȱattractedȱtoȱtheȱgreaseȱandȱbecomeȱembeddedȱ
inȱitȱ(Figureȱ8.15).ȱ
ȱ
ȱ
ȱ
ȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.15:ȱHowȱsoapsȱworkȱ
ȱ
ȱ
ȱ
with
agitation
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Onȱ theȱ otherȱ hand,ȱ theȱ hydrophilicȱ ionicȱ headȱ groupȱ isȱ notȱ attractedȱ toȱ theȱ
grease/dirt/oilȱbutȱisȱstronglyȱattractedȱtoȱtheȱwaterȱmolecules.ȱWhenȱtheȱwaterȱ
isȱstirred,ȱtheȱgrease/dirt/oilȱisȱslowlyȱreleasedȱandȱisȱcompletelyȱsurroundedȱ
byȱtheȱsoapȱmolecules.ȱTheȱsoapȱisȱableȱtoȱremoveȱtheȱgrease/dirt/oilȱbecauseȱ
ofȱtheȱcombinationȱofȱtheȱcovalentȱandȱionicȱbondsȱpresent.ȱ
ȱ
8.6.2 Natural and Synthetic Rubber
Inȱtheȱ1930s,ȱmoreȱthanȱ90ȱperȱcentȱofȱtheȱnaturalȱrubberȱusedȱinȱtheȱUnitedȱ
Statesȱ cameȱ fromȱMalaysia.ȱ Inȱ theȱdaysȱ afterȱPearlȱHarbourȱwasȱ attackedȱ inȱ
Decemberȱ 1941ȱ andȱ theȱ Unitedȱ Statesȱ enteredȱ Worldȱ Warȱ II,ȱ Japanȱ hadȱ
capturedȱ Malaysia.ȱ Asȱ aȱ result,ȱ theȱ Unitedȱ Statedȱ facedȱ itsȱ firstȱ naturalȱ
resourceȱ crisis.ȱ Theȱmilitaryȱ implicationsȱwereȱ devastatingȱ becauseȱwithoutȱ
rubberȱforȱtyres,ȱmilitaryȱaeroplanesȱandȱjeepsȱwereȱuseless.ȱȱPetroleumȬbasedȱ
syntheticȱ rubberȱ hadȱ beenȱ developedȱ inȱ 1930ȱ byȱ DuPontȱ chemistȱ Wallaceȱ
Carothersȱbutȱwasȱnotȱwidelyȱusedȱbecauseȱitȱwasȱmuchȱmoreȱexpensiveȱthanȱ
naturalȱrubber.ȱWithȱtheȱongoingȱwar,ȱȱhowever,ȱcostȱwasȱnoȱlongerȱanȱissue.ȱ
Syntheticȱ rubberȱ factoriesȱwereȱ constructedȱ acrossȱ theȱ nation,ȱ andȱwithinȱ aȱ
fewȱyears,ȱtheȱannualȱproductionȱofȱsyntheticȱrubberȱroseȱfromȱ2,000ȱtonnesȱtoȱ
aboutȱ800,000ȱtonnes.ȱ
ȱ
Naturalȱrubberȱisȱaȱpolymerȱwithȱitsȱmonomerȱunit,ȱisopreneȱ(seeȱFigureȱ8.16).ȱ
Duringȱpolymerisation,ȱthousandsȱofȱisopreneȱunitsȱwillȱjoinȱtogetherȱtoȱformȱ
poly(isoprene)ȱorȱnaturalȱrubberȱ(seeȱFigureȱ8.17).ȱ
ȱ
ȱ
Figureȱ8.16:ȱIsopreneȱunitȱ
ȱ
ȱ
ȱ
ȱ
ȱ
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ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.17:ȱPolyisopreneȱ(naturalȱrubber)ȱ
ȱ
Naturalȱrubberȱcommonlyȱhasȱhighlyȱelasticityȱbutȱisȱunstableȱtoȱheatȱandȱoxidation.ȱȱ
Whenȱitȱisȱwarmedȱaboveȱ50°C,ȱitȱsoftensȱandȱbecomesȱstickyȱandȱwillȱdecomposeȱifȱ
weȱheatȱitȱtoȱaȱtemperatureȱaboveȱ200°C.ȱTheȱpresenceȱofȱdoubleȱbondsȱinȱtheȱpolymerȱ
chainȱmakesȱitȱsusceptibleȱtoȱoxidationȱandȱbreaksȱupȱtheȱpolymerȱchains.ȱȱ
ȱ
VulcanisationȱisȱaȱmanufacturingȱprocessȱdiscoveredȱbyȱCharlesȱGoodyearȱinȱ1939ȱtoȱ
convertȱnaturalȱrubberȱintoȱaȱtoughȱusefulȱproduct.ȱInȱthisȱprocess,ȱaboutȱ1%ȱtoȱ3%ȱbyȱ
weightȱofȱsulphurȱisȱaddedȱtoȱrawȱrubberȱandȱtheȱmixtureȱisȱcarefullyȱheated.ȱSulphurȱ
atomsȱ formȱ crossȬlinksȱ betweenȱ adjacentȱ chainsȱ ofȱ rubberȱ polymerȱ atȱ theȱ carbonȬ
carbonȱdoubleȱbondsȱ(seeȱFigureȱ8.18).ȱ
Figureȱ8.18:ȱVulcanisedȱrubberȱshowingȱdisulfideȱcrossȱlinksȱ
Syntheticȱ rubberȱ isȱ anyȱ typeȱofȱ artificialȱ elastomerȱmainlyȱ synthesisedȱ fromȱ
petroleumȱ byȱ products.ȱAnȱ elastomerȱ isȱ aȱmaterialȱwithȱ theȱmechanicalȱ (orȱ
material)ȱpropertyȱthatȱitȱcanȱundergoȱmuchȱmoreȱelasticȱdeformationȱunderȱ
stressȱ thanȱ mostȱ materialsȱ andȱ stillȱ returnȱ toȱ itsȱ previousȱ sizeȱ withoutȱ
permanentȱdeformation.ȱȱSyntheticȱrubber,ȱlikeȱnaturalȱrubber,ȱhasȱusesȱinȱtheȱ
automotiveȱ industryȱ forȱ doorȱ andȱwindowȱ profiles,ȱ hosesȱ (seeȱ Figureȱ 8.19),ȱ
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103
belts,ȱ matting,ȱ flooringȱ andȱ dampenersȱ (antivibrationȱ mounts).ȱ Tableȱ 8.10ȱ
showsȱtheȱdifferencesȱbetweenȱsyntheticȱrubberȱandȱnaturalȱrubber.ȱ
ȱ
Tableȱ8.10:ȱComparisonȱofȱPropertiesȱbetweenȱManufacturedȱMaterialsȱ
(SyntheticȱRubber)ȱandȱNaturalȱMaterialsȱ(NaturalȱRubber)ȱ
SyntheticȱRubberȱ Propertiesȱ NaturalȱRubberȱ
Syntheticȱ Typeȱofȱpolymerȱ Naturalȱ
Ableȱtoȱwithstandȱ
highȱtemperatureȱ Highȱtemperatureȱeffectȱ Decomposesȱandȱ
becomeȱliquidȱ
Veryȱpermeableȱtoȱ
gasȱandȱwaterȱ
Permeabilityȱtoȱgasȱandȱ
waterȱ
Notȱpermeableȱtoȱgasȱ
andȱwaterȱ
Doesȱnotȱreactȱtoȱ
acidȱandȱalkaliȱ
Abilityȱtoȱwithstandȱ
actionsȱofȱacidȱandȱ
alkaliȱ
Reactȱtoȱacidȱandȱ
alkaliȱ
Lowȱabilityȱ
Abilityȱtoȱabsorbȱ
pressure,ȱvibrationȱandȱ
soundȱ
Highȱabilityȱȱ
Canȱbeȱvulcanisedȱ Vulcanisationȱ Easilyȱvulcanisedȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.19:ȱProductȱfromȱsyntheticȱrubberȱ
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104
8.6.3 Natural and Synthetic Fibres
Naturalȱfibresȱcanȱbeȱdefinedȱasȱsubstancesȱproducedȱbyȱplantsȱandȱanimalsȱ
thatȱ canȱbeȱ spunȱ intoȱ filament,ȱ threadȱorȱ ropeȱ andȱ inȱ aȱnextȱ stepȱbeȱwoven,ȱ
knitted,ȱ mattedȱ orȱ bound.ȱ Theȱ oldestȱ fibresȱ usedȱ byȱ mankindȱ areȱ cottonȱ
(5,000BC)ȱandȱsilkȱ(2,700BC),ȱbutȱevenȱjuteȱandȱcoirȱhaveȱbeenȱcultivatedȱsinceȱ
antiquity.ȱ Theȱmainȱ reasonsȱ forȱ theȱ popularityȱ ofȱ biocompositesȱ orȱ naturalȱ
fibreȱcompositesȱareȱtheȱavailabilityȱandȱconsistentȱqualityȱofȱaȱwideȱrangeȱofȱ
fibres,ȱ andȱ theirȱ environmentalȱ friendliness.ȱ Moreover,ȱ newȱ productionȱ
processes,ȱsuchȱasȱinjectedȱmouldedȱcomponents,ȱmakeȱitȱpossibleȱtoȱuseȱtheseȱ
materialsȱforȱindustrialȱproducts.ȱ
ȱ
Additionalȱ keyȱ advantagesȱ ofȱ naturalȱ fibresȱ areȱ theirȱ highȱ strengthȱ andȱ
stiffnessȱ perȱ weightȱ alongȱ withȱ benefitsȱ suchȱ asȱ acousticȱ isolation,ȱ safetyȱ
management,ȱ rapidȱ productionȱ andȱ potentiallyȱ lowȱ cost.ȱ Theȱ mostȱ viableȱ
structuralȱ fibresȱ typicallyȱ deriveȱ fromȱ specificallyȱ grownȱ textileȱ plantsȱ andȱ
fruitȱ trees.ȱ Thereȱ areȱ twoȱ categoriesȱ ofȱ naturalȱ fibres,ȱ vegetableȱ fibresȱ andȱ
animalȱfibres.ȱVegetableȱfibresȱareȱsubdividedȱintoȱbastȱfibresȱ(flax,ȱhemp,ȱjuteȱ
andȱkenaf)ȱleafȱfibresȱ(sisal,ȱpineapplesȱandȱhenequen),ȱgrassȱfibresȱ(bambooȱ
andȱ miscanthus),ȱ strawȱ fibresȱ (cornȱ andȱ wheat),ȱ seedȱ fibresȱ (cottonȱ andȱ
capok),ȱ woodȱ fibresȱ (pinewood)ȱ andȱ fruitȱ fibresȱ (coconut),ȱ whereasȱ animalȱ
fibresȱareȱsilk,ȱavian,ȱhairȱandȱwoolȱ(seeȱFigureȱ8.20).ȱFigureȱ8.21ȱshowsȱkenafȱ
plantsȱwhichȱisȱfromȱtheȱbastȱfibresȱcategory.ȱ
ȱȱȱ ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.20:ȱTwoȱcategoriesȱofȱnaturalȱfibresȱ
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105
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.21:ȱKenafȱplantsȱisȱaȱsourceȱofȱnaturalȱfibreȱ
ȱ
Syntheticȱfibresȱareȱmadeȱfromȱsynthesisedȱpolymersȱorȱsmallȱmolecules.ȱTheȱ
compoundsȱthatȱareȱusedȱtoȱmakeȱtheseȱfibresȱcomeȱfromȱrawȱmaterialsȱsuchȱ
asȱ petroleumȱ basedȱ chemicalsȱ orȱ petrochemicals.ȱ Theseȱ materialsȱ areȱ
polymeriseȱintoȱaȱlong,ȱlinearȱchemicalȱthatȱbondȱtwoȱadjacentȱcarbonȱatoms.ȱȱ
Differentȱ chemicalȱ compoundsȱ willȱ beȱ usedȱ toȱ produceȱ differentȱ typesȱ ofȱ
fibres.ȱ Althoughȱ thereȱ areȱ severalȱ differentȱ syntheticȱ fibres,ȱ theyȱ generallyȱ
haveȱtheȱsameȱcommonȱproperties.ȱSyntheticȱfibresȱareȱcommonlyȱveryȱheatȬ
sensitive,ȱresistantȱtoȱmostȱchemicals,ȱinsect,ȱfungiȱandȱrot.ȱItȱhasȱlowȱmoistureȱ
absorbency,ȱflameȱresistant,ȱlowȱmeltingȱtemperature.ȱSyntheticȱfibresȱareȱalsoȱ
veryȱ easyȱ toȱwashȱ andȱmaintainȱ andȱ theȱmainȱ thingȱ isȱ thatȱ itȱ isȱ oftenȱ lessȱ
expensiveȱthanȱnaturalȱfibres.ȱ
ȱ
Theȱfirstȱsyntheticȱfibreȱknownȱasȱnylonȱwasȱdiscoveredȱinȱ1931.ȱItsȱnovelȱuseȱ
asȱaȱmaterialȱforȱwomen’sȱstockingȱovershadowedȱmoreȱpracticalȱuses,ȱsuchȱasȱ
aȱ replacementȱ forȱ theȱ silkȱ inȱ parachutesȱ andȱ otherȱ militaryȱ uses.ȱ Otherȱ
commonȱsyntheticȱfibresȱareȱmodacrylic,ȱolefin,ȱacrylic,ȱpolyesterȱandȱcarbonȱ
fibre.ȱ Specialtyȱ syntheticȱ fibresȱ includeȱ vinyon,ȱ saran,ȱ spandex,ȱ vinolon,ȱ
aramids,ȱmodal,ȱ sulfar,ȱ orlon,ȱ zylon,ȱ vecran,ȱ derclonȱ andȱ rayon.ȱ Figureȱ 8.22ȱ
showsȱtwoȱexamplesȱofȱsyntheticȱfibres.ȱ
ȱ
ȱ
ȱ
ȱ
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106
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Figureȱ8.22:ȱNylonȱandȱpolyesterȱȱȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ACTIVITY 8.11
1.ȱ Compareȱandȱcontrastȱnaturalȱfibresȱandȱsyntheticȱfibres.ȱ
2.ȱ Findȱ outȱ theȱ usesȱ ofȱ allȱ commonȱ naturalȱ andȱ syntheticȱ fibre
givenȱinȱtheȱtextȱ
8.6.4 Plastics
ȱ
Withȱ aȱ recordȱ ofȱ wartimeȱ successes,ȱ plasticsȱ wereȱ readilyȱ embracedȱ inȱ theȱ
postȬwarȱyears.ȱȱInȱtheȱ1950s,ȱDacronȱpolyesterȱwasȱintroducedȱasȱaȱsubstituteȱ
forȱwool.ȱTheȱ1950sȱwasȱalsoȱtheȱdecadeȱduringȱwhichȱtheȱentrepreneurȱEarlȱ
TupperȱcreatedȱaȱlineȱofȱpolyethyleneȱfoodȱcontainersȱknownȱasȱTupperwareȱ
(seeȱFigureȱ8.23).ȱ
ȱ
ȱ
ȱ
ȱ
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107
Figureȱ8.23:ȱTupperware,ȱpolyethyleneȱfoodȱcontainerȱ
Aȱ plasticȱ materialȱ isȱ anyȱ materialȱ ofȱ aȱ wideȱ rangeȱ ofȱ syntheticȱ orȱ semiȬ
syntheticȱ organicȱ solidsȱ thatȱ areȱ mouldable.ȱ Plasticsȱ areȱ typicallyȱ organicȱ
polymersȱ ofȱ highȱ molecularȱ mass,ȱ butȱ theyȱ oftenȱ containȱ otherȱ substancesȱ
knownȱasȱadditives.ȱTheyȱareȱusuallyȱsynthetic,ȱmostȱcommonlyȱderivedȱfromȱ
petrochemicals,ȱbutȱmanyȱareȱpartiallyȱnatural.ȱTheȱamountȱofȱadditivesȱrangeȱ
fromȱzeroȱpercentageȱforȱpolymersȱusedȱtoȱwrapȱfoodsȱtoȱmoreȱthanȱ50%ȱforȱ
certainȱelectronicȱapplications.ȱExampleȱofȱadditiveȱisȱfillersȱwhichȱfunctionȱtoȱ
improveȱ performanceȱ and/orȱ reduceȱ productionȱ costs.ȱ Stabilisingȱ additivesȱ
includeȱfireȱretardantsȱtoȱlowerȱtheȱflammabilityȱofȱtheȱmaterial.ȱȱ
ȱ
Plasticsȱ areȱ usuallyȱ classifiedȱ byȱ theirȱ chemicalȱ structureȱ ofȱ theȱ polymer’sȱ
backboneȱandȱsideȱchains.ȱSomeȱimportantȱgroupsȱofȱtheseȱclassificationsȱareȱ
theȱ acrylics,ȱ polyesters,ȱ silicones,ȱ polyurethanesȱ andȱ halogenatedȱ plastics.ȱ
Otherȱ typeȱ ofȱ classificationȱ isȱ basedȱ onȱ theȱ chemicalȱ reactionȱ towardȱ heat.ȱ
Examplesȱareȱthermoplasticsȱandȱthermosettingȱpolymers.ȱThermoplasticsȱareȱ
theȱplasticsȱ thatȱdoȱnotȱundergoȱ chemicalȱ changeȱ inȱ theirȱ compositionȱwhenȱ
heatedȱ andȱ canȱ beȱmouldedȱ againȱ andȱ again.ȱ Thisȱ typeȱ ofȱ plasticsȱ includesȱ
polyethylene,ȱ polypropylene,ȱ polystyreneȱ andȱ polyvinylchloride.ȱ
Thermosettingȱ polymersȱ canȱ meltȱ andȱ takeȱ shapeȱ once.ȱ Afterȱ theyȱ haveȱ
solidified,ȱ theyȱ stayȱ solidȱ becauseȱ inȱ theȱ thermosettingȱ process,ȱ aȱ chemicalȱ
reactionȱ occursȱ thatȱ isȱ irreversible.ȱ Anȱ exampleȱ isȱ theȱ vulcanisedȱ rubber.ȱȱ
Otherȱclassificationsȱareȱbasedȱonȱqualitiesȱthatȱareȱrelevantȱforȱmanufacturingȱ
andȱalsoȱonȱtheȱphysicalȱproperties.ȱ
ȱ
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Byȱ theȱ 1960s,ȱ aȱdecadeȱ ofȱ environmentalȱ awakening,ȱmanyȱpeopleȱ beganȱ toȱ
recogniseȱ theȱ negativeȱ attributionȱ ofȱ plastics.ȱ ȱ Beingȱ cheap,ȱ disposable,ȱ andȱ
nonȬbiodegradable,ȱplasticȱreadilyȱaccumulatedȱasȱlitterȱandȱasȱlandfill.ȱWithȱ
petroleumȱsoȱreadilyȱavailableȱandȱinexpensive,ȱhowever,ȱandȱwithȱaȱgrowingȱ
populationȱ ofȱplasticȬdependentȱbabyȱboomers,ȱ littleȱ stoodȱ inȱ theȱwayȱ ofȱ anȱ
everȬexpandingȱ arrayȱ ofȱ plasticȱ consumerȱ products.ȱ Byȱ 1977,ȱ environmentalȱ
concernsȱstartedȱtoȱgrow,ȱandȱinȱ1980sȱplasticsȱrecyclingȱprogrammesȱbeganȱtoȱ
appear.ȱ Researchesȱ toȱ produceȱ biodegradableȱ plasticsȱ haveȱ beenȱ doneȱ
progressively.ȱAnȱexampleȱisȱtheȱuseȱofȱstarchȱpowderȱmixedȱwithȱplasticsȱasȱaȱ
fillerȱtoȱallowȱitȱtoȱdegradeȱmoreȱeasily,ȱbutȱitȱstillȱdoesȱnotȱleadȱtoȱcompleteȱ
breakdownȱ ofȱ theȱ plastic.ȱ Someȱ researchersȱ haveȱ actuallyȱ geneticallyȱ
engineeredȱbacteriaȱthatȱsynthesiseȱaȱcompletelyȱbiodegradableȱplastic.ȱȱ
ȱ
ȱ
SELF CHECK 8.6
ȱ ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
ȱ
Searchȱ fromȱ theȱ Internetȱ orȱ otherȱ resourceȱ onȱ research/productsȱ of
biodegradableȱplasticsȱthatȱhasȱbeenȱdoneȱinȱMalaysia.ȱ
x Physicalȱ propertiesȱ ofȱ materialsȱ includeȱ elasticity,ȱ shininess,ȱ buoyancy,ȱ
waterȱabsorbency,ȱelectricalȱconductivityȱandȱheatȱconductivity.ȱȱȱ
x Otherȱ physicalȱ propertiesȱ ofȱmaterialsȱ includeȱ hardness,ȱ toughnessȱ andȱ
brittleness,ȱstrength,ȱflexibilityȱandȱsolubility.ȱ
x Elasticityȱisȱtheȱabilityȱofȱaȱmaterialȱtoȱreturnȱtoȱitsȱoriginalȱshapeȱandȱsizeȱ
afterȱbeingȱbent,ȱtwisted,ȱstretchedȱandȱsqueezed.ȱMaterialsȱthatȱareȱableȱtoȱ
returnȱtoȱtheirȱoldȱshapeȱwhenȱforceȱisȱnoȱlongerȱappliedȱareȱcalledȱelasticȱ
materials.ȱ
x Someȱmaterialsȱareȱshinyȱandȱsomeȱareȱnot.ȱ
x Materialsȱ canȱ alsoȱ beȱ dividedȱ intoȱ threeȱ typesȱ accordingȱ toȱ itsȱ abilityȱ toȱ
allowȱlightȱtoȱpassȱthroughȱit.ȱTheseȱareȱtransparentȱmaterials,ȱtranslucentȱ
materialsȱandȱopaqueȱmaterials.ȱ
x Buoyancyȱisȱtheȱabilityȱofȱmaterialsȱtoȱfloatȱinȱliquid.ȱ
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109
x Materialsȱwhichȱ canȱabsorbȱwaterȱ areȱknownȱasȱabsorbentȱmaterialsȱandȱ
materialsȱ whichȱ cannotȱ absorbȱ waterȱ areȱ knownȱ asȱ nonȬabsorbentȱ
materials.ȱ
x Aȱ materialȱ thatȱ allowsȱ electricityȱ toȱ passȱ throughȱ itȱ isȱ aȱ materialȱ thatȱ
conductsȱelectricity.ȱ
x Aȱmaterialȱ thatȱ allowsȱ heatȱ toȱ passȱ throughȱ itȱ easilyȱ isȱ aȱmaterialȱ thatȱ
conductsȱheat.ȱ
x Magnetismȱ isȱ theȱpropertyȱ ofȱmaterialsȱ toȱ attractȱ iron,ȱ forȱ example,ȱ ironȱ
oxide,ȱcobalt,ȱnickelȱandȱcertainȱtypesȱofȱalloy.ȱ
x Knowledgeȱaboutȱtheȱpropertiesȱofȱmaterialsȱisȱveryȱimportant,ȱespeciallyȱ
inȱchoosingȱsuitableȱmaterialsȱtoȱmakeȱvariousȱobjects.ȱ
x Theȱpropertiesȱofȱmaterialsȱhaveȱmanyȱusefulȱapplicationsȱinȱourȱdailyȱlife.ȱ
x Materialsȱareȱmadeȱofȱthousandsȱofȱsmallȱparticlesȱcalledȱatoms.ȱ
x Materialsȱ canȱ beȱ dividedȱ intoȱ threeȱ categoriesȱ accordingȱ toȱ theirȱ
componentsȱofȱatom:ȱelement,ȱcompoundȱandȱmixture.ȱ
x Materialsȱ canȱbeȱ classifiedȱ intoȱ twoȱ typesȱ accordingȱ toȱ theirȱuse:ȱnaturalȱ
materialsȱandȱmanȬmadeȱmaterialsȱorȱmanufacturedȱmaterials.ȱȱ
x Naturalȱ materialsȱ originateȱ fromȱ soil,ȱ rocks,ȱ water,ȱ plant,ȱ animalȱ orȱ
minerals.ȱȱ
x Manufacturedȱ materialsȱ areȱ madeȱ fromȱ aȱ mixtureȱ ofȱ naturalȱ materialsȱ
throughȱchemicalȱprocesses.ȱ
x Manufacturedȱmaterialsȱareȱdesignedȱaccordingȱtoȱtheȱneedsȱofȱtheȱmarket.ȱ
x Preservationȱ refersȱ toȱ theȱ effortȱ toȱ maintainȱ naturalȱ resourcesȱ inȱ theirȱ
originalȱstateȱorȱinȱgoodȱcondition.ȱ
x Conservationȱ refersȱ toȱ theȱ sustainableȱ useȱ andȱ managementȱ ofȱ naturalȱ
materialsȱtoȱpreventȱloss,ȱwastageȱorȱdamage.ȱ
x Compositeȱmaterialsȱ areȱ theȱmaterialsȱ whichȱ combineȱ theȱ propertiesȱ ofȱ
twoȱsubstancesȱinȱorderȱtoȱgetȱtheȱexactȱpropertiesȱrequiredȱforȱaȱparticularȱ
job.ȱ
ȱ
314

110
x Saponificationȱisȱtheȱprocessȱofȱmakingȱsoapȱbyȱheatingȱnaturalȱfatsȱandȱoilȱ
withȱaȱstrongȱalkali.ȱ
ȱ
x Polymerisationȱ isȱ theȱ processȱ ofȱ isopreneȱ unitsȱ joinȱ togetherȱ toȱ formȱ
poly(isoprene)ȱorȱnaturalȱrubber.ȱ
x Syntheticȱ rubberȱ isȱ anyȱ typeȱ ofȱ artificialȱ elastomerȱ mainlyȱ synthesisedȱ
fromȱpetroleumȱbyȱproductsȱwithȱbetterȱqualityȱthanȱnaturalȱrubber.ȱ
x Naturalȱ fibresȱ isȱ substancesȱproducedȱbyȱplantsȱ andȱ animalsȱ thatȱ canȱbeȱ
spunȱ intoȱ filament,ȱ threadȱorȱ ropeȱ andȱ inȱ aȱnextȱ stepȱbeȱwoven,ȱknitted,ȱ
mattedȱ orȱ bound,ȱ whileȱ syntheticȱ fibreȱ areȱ madeȱ fromȱ synthesisedȱ
polymersȱorȱsmallȱmolecules.ȱ
x Aȱ plasticȱmaterialȱ isȱ anyȱ ofȱ aȱwideȱ rangeȱ ofȱ syntheticȱ orȱ semiȬsyntheticȱ
organicȱ solidsȱ thatȱ areȱmouldable.ȱ Allȱ plasticsȱ areȱ polymersȱ butȱ notȱ allȱ
polymersȱareȱplastics.ȱ
ȱ
ȱ
Abioticȱ
Bioticȱ
Componentȱ
Compositeȱmaterialsȱ
Conservationȱ
Elementȱ
Fibreȱ
Manufacturedȱmaterialȱ
Materialȱȱ
Mixtureȱ
Naturalȱmaterialȱ
Plasticsȱ
Preservationȱ
Rawȱmaterialȱ
Rubberȱ
Soapȱ
Syntheticȱ
ȱ
315

111
ȱ
AliasȱAbdullah,ȱFaujanȱAhmad,ȱȱNurȱHudaȱFaujan.ȱ (2007).ȱTotalȱProUPSR:ȱ
ScienceȱYearȱ4,ȱ5ȱandȱ6.ȱPetalingȱJaya:ȱSasbadi.ȱ ȱ
Earl,ȱB.,ȱȱWilford,ȱD.ȱ(2009).ȱȱIGCSEȱchemistry.ȱUK:ȱHodderȱEducation.ȱȱ
ȱ ȱ
Eng,ȱN.ȱH.,ȱȱLim.,ȱY.ȱC.ȱ(2007).ȱFocusȱsuperȱchemistry.ȱBangi:ȱPenerbitanȱPelangi.ȱ
ȱ
Farrow,ȱ S.ȱ (1996).ȱ Theȱ reallyȱ usefulȱ scienceȱ book:ȱ Aȱ frameworkȱ ofȱ knowledgeȱ forȱ
primaryȱteacher.ȱLondon:ȱFalmerȱPress.ȱ ȱ
Heimler,ȱ C.ȱ H.,ȱ ȱ Neal,ȱ C.ȱ D.ȱ (1979).ȱ Principlesȱ ofȱ scienceȱ (4thȱ ed.).ȱ Ohio:ȱ
CharlesȱE.ȱMerrillȱPublishingȱCo.ȱȱ
Joesten,ȱM.,ȱȱHogg,ȱJ.ȱ(2011).ȱChemȱinȱyourȱworldȱ(Studentȱed.).ȱUSA:ȱBrooksȱ
ColeȱCengageȱLearningȱ
Johnson,ȱK.,ȱAdmson,ȱS.,ȱȱWilliams,ȱG.ȱ(2000).ȱSpotlightȱscienceȱ7.ȱCheltenham:ȱ
NelsonȱThornes.ȱ ȱ
Knapp,ȱB.ȱ(1996).ȱScienceȱinȱourȱworld:ȱMaterials.ȱLondon:ȱRegencyȱPublishingȱ
Group.ȱ ȱ
Ramsden,ȱ E.ȱ (2001).ȱ Keyȱ science:ȱ Chemistryȱ (3rdȱ ed.).ȱ Cheltenham:ȱ Nelsonȱ
Thornes.ȱ
Sitiȱ Sarahȱ Shahrel.ȱ (2007).ȱ UPSRȱ bilingualȱ science:ȱ Yearȱ 4.ȱ Shahȱ Alam:ȱ Arahȱ
Pendidikan.ȱ
Suchocki,ȱJ.ȱ(2007).ȱConceptualȱchemistryȱ(3rdȱed.).ȱNewȱJersey:ȱPearson.
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