ENERGY AND MATTER
Matter and energy
Experiment 1: To show that matter has a mass and occupies space.
Matter is anything that has a mass and occupies space (volume). Its mass can be measured in
kilograms (kg) with an electronic balance. Its volume can be measured directly using appropriate
laboratory apparatus. Matter is made up of tiny, invisible particles.
The properties of matter
All matter has physical properties. A physical property is one that a person can measure without
changing the matter. Colour, amount and temperature are examples of physical properties.
All matter also has chemical properties. A chemical property tells how matter will change under
special conditions. For example, iron turns to rust if it sits out in the rain. Paper and wood burn to
ashes if they touch a flame. Burning and rusting are called chemical reactions. Chemical reactions
change matter into new types of matter.
States of matter
Matter can exist in the solid, the liquid and the gas states.
A solid has a fixed shape and a fixed volume. It does not flow. A solid cannot be compressed.
A liquid does not have a fixed shape: it will take the shape of its container, but its volume is fixed. A
liquid can flow but it cannot be compressed.
A gas has neither a fixed shape nor a fixed volume: it will fill the entire volume of any closed
container, taking its shape as well. A gas can flow and it can even be compressed.
The solid state
In a solid, the particles are packed very closely together in an orderly (regular) manner. These
particles can only vibrate or rotate about a fixed position. There are very strong forces of attraction
between solid particles.
The liquid state
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In a liquid, the particles are packed close together in a disorderly (random) manner. These particles
can move quite freely among each other, but they cannot escape from the liquid. There are strong
forces of attraction between liquid particles.
The gas state
In a gas, the particles are far apart and arranged in a random manner. These particles move freely in
all directions at very high speeds. There are weak forces of attraction between gas particles.
Change of state
Experiment 2: To show that a solid must be heated for it to become a liquid (melting).
Experiment 3: To show that a liquid must be heated for it to become a gas (boiling).
During any change of state, the temperature does not change.
Melting
Melting is the change of state from solid to liquid at constant temperature. The temperature at
which melting occurs is called the melting point of the solid. Melting happens when the solid
particles gain heat energy and they vibrate so fast that they can break their orderly arrangement.
Boiling
Boiling is the change of state from liquid to gas at constant temperature. The temperature at which
boiling occurs is called the boiling point of the liquid. Boiling happens when the liquid particles gain
heat energy and they move so fast that they can escape into the air.
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Other changes of states
SOLID
Freezing
(solidification)
melting
condensation
(reverse sublimation)
sublimation
boiling
LIQUID
GAS
condensation
Freezing or solidification is the change of state from liquid to solid at constant temperature.
Condensation is the change of state from gas to liquid (or solid) at constant temperature.
Certain solids, like ammonium chloride, solid carbon dioxide (dry ice) or iodine do not melt when
heated—they change directly from solid to gas: these substances sublime on heating. Sublimation is
the change of state from solid to gas at constant temperature.
Experiment 4: To show that solid ammonium chloride sublimes on heating.
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THE ENVIRONMENT
Composition, properties and importance of air
Experiment 5: To test for the presence of oxygen in air.
Experiment 6: To test for the presence of carbon dioxide in air.
Dry air is a mixture of gases whose composition, by volume is:
CONSTITUENT
PERCENTAGE BY VOLUME
nitrogen
78%
oxygen
21%
noble gases (mainly argon)
less than 1%
carbon dioxide
0.034%
Air also contains variable amounts of water vapour and air pollutants.
Air has no colour, taste or smell.
A piece of paper will catch fire and burn in air due to the presence of oxygen in it. We say oxygen
supports combustion.
Air will also turn limewater milky because it contains carbon dioxide. If we bubble air through
limewater this liquid will turn milky due to the presence of carbon dioxide in it.
All living things need air to breathe. Animals and plants would die without it. Insects, birds and
aeroplanes can fly because there is air all around.
Sources, properties and uses of water
Experiment 7: Physical and chemical properties of water demonstrated.
Water is the most abundant and important liquid on Earth, as all living organisms make use of water.
We obtain our water for domestic use from reservoirs, lakes and rivers. We can also obtain it from
the sea by a process called desalination.
Pure water is a clear, colourless, odourless liquid that freezes at 0 0C and boils at 100 0C at
atmospheric pressure. It can dissolve many substances in it to form an aqueous solution.
In the home, water is used for drinking, cooking and washing. In industry water is used for cleaning,
for irrigation and for cooling. Water is also used as a solvent in the manufacture of chemicals and
drugs.
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AN INTRODUCTION TO THE LANGUAGE OF CHEMISTRY
Elements
Definition of an element
An element is a pure substance that cannot be broken down into any simpler substances by any
ordinary chemical process.
Properties of elements
Elements constitute the building blocks of all known substances. An element is made up of its own
types of atoms and each element has a name and a chemical symbol. 118 elements are known to
scientists, out of which 92 elements are naturally found on Earth, while the remaining 26 are
artificially made elements.
The diagram below shows how we can represent an element in the gaseous state:
Examples and uses of some common elements
The table below summarises the symbols, nature, appearance, physical states as well as the uses of
some common elements:
ELEMENT
SYMBOL
METALLIC
NATURE
APPEARANCE
PHYSICAL
STATE
USES
Aluminium
Al
metal
grey, shiny
solid
To make aircraft
Bromine
Br
non-metal
reddish, brown
liquid
In flame retardants
Carbon
C
non-metal
black
solid
To make steel
Chlorine
Cl
non-metal
yellowish-green
gas
To kill germs in water
Copper
Cu
metal
solid
To make water pipes
Gold
Au
metal
reddish-brown,
shiny
golden, shiny
solid
To make jewellery
Helium
He
non-metal
colourless
gas
In airships and balloons
Hydrogen
H
non-metal
colourless
gas
As a fuel in space shuttles
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ELEMENT
SYMBOL
METALLIC
NATURE
APPEARANCE
PHYSICAL
STATE
Iron
Fe
metal
grey, shiny
solid
Magnesium
Mg
metal
grey, shiny
solid
Mercury
Hg
metal
silvery, shiny
liquid
Nitrogen
N
non-metal
colourless
gas
Oxygen
O
non-metal
colourless
gas
Silicon
Si
non-metal
grey
solid
Sodium
Na
metal
grey, shiny
solid
USES
To make ships, bridges and
buildings
Used in outdoor emergency
fires
To make thermometers and
barometers
To make fertilisers
Used in hospitals for
breathing
Used to make parts for
electronic equipment
Used in some street lighting
Sulfur
S
non-metal
yellow
solid
To make sulfuric acid, which
is used in car batteries
Zinc
Zn
metal
grey, shiny
solid
To make dry cells
Classification of elements
As solids, liquids and gases
Elements can be classified as solids, liquids or gases. For example, iron and carbon are solids.
Mercury and bromine are liquids. Oxygen and nitrogen are gases.
As metals and non-metals
They can also be classified as metals and non-metals. Examples of metals or metallic elements are
iron, mercury, copper, gold, aluminium, etc. Examples of non-metals or non-metallic elements are
carbon, sulfur, bromine, chlorine, oxygen, etc.
In a table called the Periodic Table
Similar elements can also be grouped together in a table called the Periodic Table. The vertical
columns in a Periodic Table are called ‘Groups’. The horizontal rows in the Periodic Table are called
‘periods’.
Experiment 8: Observing some metallic elements.
Experiment 9: Observing some non-metallic elements.
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Compounds
Definition of a compound
A compound is a pure substance, which contains two or more elements chemically combined
together.
Properties of compounds
A compound is made up of more than one type of atoms and each compound has a name and a
chemical formula. For example, water is a compound and has formula H2O. Carbon dioxide is
another compound of formula CO2.
When compounds are formed, energy is either given out or absorbed.
A compound does not retain the properties of the elements it contains. Magnesium is a metallic
element and it appears as a grey shiny solid. Oxygen is a non-metallic element and it appears as a
colourless gas. When magnesium is burned in the oxygen of the air, a chemical reaction occurs and a
new substance is formed. This new substance, which is different from magnesium and oxygen,
appears as a white powder and is given the name magnesium oxide.
Compounds can be broken down into simpler substances using heat (thermal decomposition) or
electricity (electrolysis). If we melt the white solid magnesium oxide and then pass an electric
current through it, we can get back the magnesium and the oxygen gas.
The diagram below represents a compound in the gaseous state. It is made up of two different
elements chemically combined together.
Experiment 10: To demonstrate some common laboratory compounds.
Experiment 11: To show the formation of the compound magnesium oxide from its elements.
Experiment 12: To show that a compound can be broken down using electricity.
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Mixtures
A mixture is an impure substance containing two or more elements or compounds which are not
chemically combined together. The elements or compounds present in the mixture may vary in
proportion, yet it will still be a mixture.
A mixture retains the original properties of each element or compound present in it. For example,
air, which is a mixture of gases, will allow things to burn in it because it contains oxygen. Air will also
turn limewater milky because it contains carbon dioxide.
When a mixture is prepared no heat or light energy is given out or absorbed.
Examples of common mixtures are seawater, petroleum, soap, beer, etc.
The above diagram shows a mixture in the gaseous state. This mixture contains two different
elements and one compound.
The elements or compounds present in a mixture can be removed or separated by physical means
like filtration, distillation, chromatography, etc.
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SUSTAINABLE LIVING—USE OF RESOURCES
Renewable and non-renewable resources
A renewable resource is one which can be used without the risk of finishing all. Examples of
renewable resources are sunlight, water, air, plants and animals. We use sunlight as an energy
source. Humans use water for drinking and cleaning purposes. We use plants and animals as our
food supply. Living things, such as trees, grasslands and wildlife are examples of renewable
resources because they can all reproduce. If a tree is cut down, another can be planted in its place.
Animals have offspring that live on after the parents have died.
A non-renewable resource is one that cannot be replaced after use. Iron ore, soil, stone, coal
petroleum, oil and gases are examples of non-renewable resources because they can take thousands
or millions of year to form. They are considered non-renewable because people use them faster
than they can form. Humans use iron and metal ores to make tools and household objects. We use
coal, petroleum and oil as a source of fuel and to make useful chemicals. Soil is useful to man in
agriculture.
Natural resources and man-made materials
Experiment 13: Sorting a group of items as natural or man-made.
Natural resources are materials that can be found within the environment. Some examples of
natural resources include air, wind, atmosphere, animals, fossil fuels, diamond, rock, minerals, oil,
forestry, soil, water, oceans, lakes, groundwater, and the Sun. Diamond, rock and minerals are used
in industry. We obtain wood from our forests. Every man-made product is composed of natural
resources at its fundamental level.
Man-made resources are a type of resource that does not occur naturally and is made by humans.
Man-made resources include plastic, banknotes, vaccines, medicines, roads, cities, parks, roofs, rails,
pencils, coins, pins, glasses, keys, doors, sheets, radio, cable, violin, guitars, clothing, shoes, socks,
jewellery, perfume, hand bags, piers, docks, boats, cars, bikes, staplers, paper clips, ink pens,
notebooks, books, bookmarks, wigs and candles. There are hundreds of man-made resources that
cannot be found in the wild and do not occur without human assistance.
Protection of the environment
To protect the environment:
1. Do not waste food.
2. Turn off water when you are not using it. Check for leaks and repair them at once. Use lowflow toilets to save water at every flush. Take shorter showers whenever it is possible.
3. Buy less stuff that you do not really need.
4. Avoid using disposable items, to minimise landfill sites. Donate or share usable household
items rather than sending them to a landfill. Avoid using plastic whenever you can. Recycle
or reuse. Use rechargeable batteries instead of disposable ones. Use reusable bottles for
water. Make and use your own composts to reduce the use of chemical fertilisers and to
avoid filling your litter box unnecessarily.
5. Get in the habit of walking or riding your bike for short, local trips. Use buses or high
occupancy vehicles to reach a destination.
6. Use renewable energy sources like biomass, hydroelectric energy, solar energy, tidal energy
or wind energy.
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7. Switch off anything that uses electricity, if you are not currently using it. This goes for lights,
televisions, computers, printers, and so on. Instead of using air conditioners, use natural
ventilation or a fan to keep cool. Switch to compact florescent or LED light bulbs.
8. Do not use chemical pesticides, herbicides or chemicals.
9. Plant a tree. Stop buying newspapers if you want to save our forests.
Managing resources appropriately (The 3R’s of the Environment)
To manage resources appropriately we have to Reduce, Reuse and Recycle.
Reducing the amount of waste you produce is the best way to help the environment. Instead of
buying something, borrow if you are not going to use it often. Buy products that do not use a lot of
packaging. Print less and read more online to save paper and to save our forests.
Instead of throwing things away, try to find ways to use them again! Store food in reusable plastic
containers. Bring reusable cloth sacks to the store with you instead of taking home new paper or
plastic bags. Do not throw out clothes, toys, furniture and other things that you do not want
anymore. Somebody else can probably use them. You can bring them to a centre that collects
donations or give them to friends. Use all writing paper on both sides.
Recycled items are put through a process that makes it possible to create new products out of the
materials from the old ones. Many of the things we use every day, like paper bags, soda cans and
milk cartons, are made out of materials that can be recycled. You can help the environment by
buying products that contain recycled materials. Recyclables include glass, newspaper, aluminium,
cardboard and a surprising array of other materials. Rinse out, sort your recyclables and put them in
the appropriate bin available in your school or in your area.
Conservation of natural resources
Conservation refers to ways to protect and preserve things found in nature.
Conservation of renewable resources helps people manage them so that they are kept in good
supply. If a tree is cut down, another can be planted in its place.
Conservation of non-renewable resources involves slowing down the rate at which these things are
being used up. It also involves finding other products that can serve the same purpose. For example,
less petroleum would be needed if other types of fuel became more readily available.
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SCIENCE AND TECHNOLOGY
Major discoveries in science
Experiment 9: Some chemical elements demonstrated.
In 1869 a Russian scientist named Dmitry Mendeleyev proposed a way of organising the elements
based on their chemical properties. The arrangement of elements that evolved from his idea is called
the Periodic Table. It has become a principal tool for thinking about elements and the properties
associated with them. He was able to use this to predict the existence of undiscovered elements. In
1913, the table was made more accurate by Henry Moseley of England.
Major inventions in science
In March 1909, Chemist Fritz Haber placed a sheet of osmium in a steel chamber, pumped in a mix of
nitrogen and hydrogen gases, and cranked up the heat and pressure. Then, out flowed ammonia, the
elusive raw material for producing synthetic fertilizer. Haber managed to create the necessary
conditions to transform nitrogen gas into a form digestible by plants. Once implemented on an
industrial scale, ammonia synthesis enabled the widespread fertilization of croplands for decades.
Overuse of technology: the problem of global warming
The Earth's atmosphere traps energy from the sun. Carbon dioxide and other gases in the air do this
trapping and they are therefore called greenhouse gases. Without these gases, too much heat would
go back into space and living things could not survive. However, as more greenhouse gases get into
the air, they also trap more heat. This leads to global warming.
People are burning fossil fuels to power factories, run cars, produce electricity and heat houses. As
fossil fuels burn, they release carbon dioxide into the atmosphere. Also, people are cutting down
many trees, which means that less carbon dioxide is being taken out of the atmosphere.
Warmer weather could make glaciers and the polar ice caps melt, causing sea levels to rise
drastically. Plants, animals and buildings along coastlines could all be in danger. People in areas that
are already warm might suffer from more heat-related health problems.
We can help to reduce global warming by sharing cars or taking a bus, thereby putting fewer vehicles
on the road. Buying appliances that have been designed to save energy helps directly. Turning off
lights, televisions and other electrical items when not in use puts less demand on electric companies
to supply power.
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