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Natural Science and Technology
Grade 5
Term 3
Energy and Change and Systems and Control
CONTENTS
Topic 10
Topic 11
Stored energy in fuels
Energy and electricity
Unit 1: Fuels
Unit 1: Cells and batteries
Unit 2: Burning fuels
Unit 2: Mains electricity
Unit 3: Fire safety
Unit 3: Safety with
Topic 12
Topic 13
Energy and movement
Systems for moving things
Unit 1: Stored energy
Unit 1: Wheels and axles
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Topic 10
Stored energy in fuels
Unit: 1 Fuels
Key Words
fuel - a substance that can be eaten or burned to produce energy
stored energy - energy that is stored in something, e.g. food
input energy - the energy needed to start a fuel burning
output energy - the energy that is produced when fuel burns
Fuels are used in many different ways in our day to day lives. Fuels are substances that
can be burned to produce heat or energy. Energy is stored in fuel. We call this, stored
energy. The energy is slowly released when the fuel is burnt.
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Food is a fuel that contains energy. It is seen as fuel for the body. Food is broken down
with the aid of oxygen and energy is released into the body.
Fuels are sources of useful energy
The helpful sources of energy that we use on a daily basis include coal, natural gas and
paraffin. We use the stored energy in these fuels for many different things. We heat and
light our homes using this energy. We are even able to use it to cook and prepare meals.
Candle wax is also a fuel. Candles were originally made of beeswax or different plant
waxes. Today they are made from paraffin wax. The energy is stored in the wax and
released when the candle burns. Light and heat energy is released.
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Cars use petrol to make the car move. Stored energy in the petrol is released when the
car’s engine burns this fuel. The car is then able to move.
Examples of fuels and what they are used for:
FUEL
Petrol
Firewood
Gas
Paraffin
Candle wax
Coal
Food
USE
To run engines
Heating and cooking
Heating and cooking
Lighting, heating and cooking
Lighting
Making electricity at power stations and heating
Providing energy to keep our bodies moving and growing
Fuels need energy to start
them burning. A candle
needs a burning match to
set its wick alight. The
match provides what we
call input energy.
When fuels start to burn,
the stored energy inside
is released and changed
into
other
forms
of
energy like heat and
light. We call this output
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Unit 2: Burning fuels
Key Words
extinguish - to put out
fire-fighters - people who are trained to put out uncontrolled fires
The three most important elements for a fire are:
1. Fuel, e.g. wood
2. Heat, e.g. matches (input energy)
3. Oxygen
Fuel, heat and oxygen form the fire triangle. If any of these are taken away, the fire will be
extinguished. This means the fire will stop burning.
A candle will burn if a match (heat source) is brought near the candle wick. The heat from the
flame melts the wax and turns a small amount of the candle wax fuel into gas. This gas mixes
with the oxygen in the air to make a flame.
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The heat of the flames melts the top of the candle wax (fuel) and turns it into a liquid form. It
will continue burning until there is no wax left.
Fire-fighters are people who assist in putting out uncontrolled fires. To stop a fire from
burning the fire-fighter has to stop the oxygen supply. Water is usually used to extinguish a
fire. The water will cut off the oxygen supply as well cool the fire and remove the heat from it.
Unit 3: Safety with fire
How to prevent fires
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1. Do not play with matches, lighters or any flammable liquids.
2. Fuel such as petrol should never be poured onto a burning fire.
3. Candles must always be placed in sturdy candleholders. Never
put a burning candle near flammable objects such as curtains or
books.
4. Always place fireguards in front of fireplaces.
5. Never dry clothes on or near a heater or cooker.
6. Cooking should always be done under adult supervision.
Never leave pots unattended.
7. If you suspect a gas leak from a cylinder, turn off the supply
and call a gas supplier.
8. Do not use damaged electrical appliances.
9. Ensure that a fire is extinguished after having a braai or making an open fire.
Topic 11
Energy and electricity
Unit1: Cell and batteries
Key words
electrochemical cell – changes chemical energy into electricity
battery - a source of stored energy that is made of one or more cells
switch - controls the electricity in an electric circuit
electrical circuit – a system that provides a path for the transfer of electricity
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Torches run on batteries. A battery is made up of one or
more cells. There is energy in batteries. An electrochemical
cell changes the energy in chemicals into electricity. The
energy in the battery is transferred to the bulb of the torch.
The electricity is changed into light energy and heat energy.
The energy flow is controlled by a switch. The bulb will
stop working when the stored energy in the batteries is
used up.
How to dispose of old batteries safely
Chemicals that are harmful to the environment can leak out of old batteries. Soil
and water is polluted and people’s health is affected.
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Never put batteries in an open fire as they can explode.
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Some shops and community waste centres collect old batteries. It is taken
to be recycled or to special waste disposal sites that store dangerous
The parts inside a torch that carry electricity are joined together in a loop that begins and
ends at the batteries. The system is called an electrical circuit.
The different parts are called components. For electricity to flow through a circuit, all the
components must be connected to each other.
Unit 2: Mains electricity
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Key words
electricity distribution box - the place where electricity is connected to the electrical
circuits in a building
wall socket - the part of the wall where an electrical appliance can be connected to an
electrical circuit
The electricity we use in a house is called mains electricity. We use mains electricity to
light our homes and run appliances like televisions. We plug appliances into a socket in
the wall.
Mains electricity comes from power stations
Mains electricity is made in power stations.
A power station needs a source of energy.
Coal is the main source of energy in South African homes.
The electricity is transferred from the power stations to substations and then to places
where it is needed such as homes, schools, factories etc. through cables called
transmission lines.
These transmission lines are supported and carried by huge structures called pylons.
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Unit 3: Safety with electricity
THE VOLTAGE OF MAINS ELECTRICITY FROM
THE WALL SOCKET IS HIGH ENOUGH TO KILL
YOU!
How to use electricity safely
1. Never touch the metal terminals of plugs or bare wires.
2. Do not put things such as your fingers or anything made of metal into electric sockets.
3. Do not let bare electrical wires touch each other as they may start a fire.
4. Always keep electrical wires dry.
5. Do not touch electrical wires electrical wires when your hands are wet.
6. Never use electrical appliances when you are bathing.
7. Do not overload a socket by using too many appliances.
8. Never try to repair electrical cords and plugs with electrical tape.
9. Replace worn, cracked or broken plugs and cables.
10. Do not pull a plug out by the cord or cable.
11. Turn the switch off at the wall socket before removing the plug.
12. Keep electrical cords away from hot things like stoves.
13. Make sure that lights are switched off when you change a light bulb.
14. Never place an electrical cord under a carpet, as the wires can wear through.
CAUTION
Never play near or enter a place where
this sign is displayed.
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Topic 12
Energy and movement
Unit 1: Stored energy
Key Words
elastic - a material that returns quickly to its original shape after it has been bent or stretched
twist – to wind something around or through an object
compress – to squash something and make it flat
release – to let something go
Elastic bands and springs
Elastic bands and springs are used to move things. Before
things are able to move we will either have to twist or stretch
it. When we stretch or twist it, we give it the energy to make
it move. When we release or let go of the elastic band, the
stored energy is changed into movement energy.
The same thing happens with springs. When we
compress or squash a spring and let it go, it moves.
We give the spring energy to move when we
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compress it. Releasing the spring allows the stored energy to change into movement
energy.
Topic 13
Systems for moving things
Unit 1: Wheels and axels
Key Words
system – two or more parts that work together for a common purpose or function
mechanism – parts of a machine that has a particular job to make a machine work
axle – a rod attached to a wheel and that goes through the middle of the wheel
fulcrum – the centre point on a wheel
turning axle – an axle that turns when the wheels turn
fixed axle – an axle that does not move; the wheel turns on the axel
A system is something that is made from two or more parts that work together to carry out
a function.
Example: Frame + wheels + pedals + brakes + seat + gears = bicycle
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Many vehicles are systems with different parts that work together. Each moving part or
mechanism does a special task to help the vehicle move. The most important system of
mechanisms in a vehicle is the wheels and axles.
The wheel and axle is a simple system made of a wheel
attached to a rod. The rod is called an axle. The axle goes
through the middle of the wheel. The wheel acts as a
lever rotating around the fulcrum or the centre point.
fulcrum
In early vehicles, the axle was a pole of wood that fitted in the centre of the wheels. When
the wheels turned, the axle also turned. We call this a turning axle.
Most wheels today have fixed axles. This means that the axle does not move, but the
wheels spin on the axle.
Did you know...?
Space travel would not have been possible
without the invention of the wheel.
Long ago
Today
Bibliography: Platinum Natural Sciences and Technology- Maskew Miller and Longman
Day by Day Natural Sciences and Technology- Maskew Miller and Longman
Thunderbolt kids Natural Science and Technology- Dept of Basic Education
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