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Contents

Topic 10: Stored energy in fuels .......................................................................................... 2

Unit: 1 Fuels ..................................................................................................................... 2

Fuels are sources of useful energy ............................................................................... 3

Examples of fuels and what they are used for .............................................................. 4

Unit 2: Burning fuels ......................................................................................................... 4

Unit 3: Safety with fire ...................................................................................................... 6

How to prevent fires ...................................................................................................... 6

Topic 11: Energy and electricity ........................................................................................... 6

Unit1: Cell and batteries ................................................................................................... 6

Unit 2: Mains electricity .................................................................................................... 8

Mains electricity comes from power stations ................................................................ 8

Unit 3: Safety with electricity ............................................................................................ 8

How to use electricity safely ......................................................................................... 8

Topic 12: Energy and movement ......................................................................................... 9

Unit 1: Stored energy ....................................................................................................... 9

Topic 13: Systems for moving things ................................................................................. 10

Unit 1: Wheels and axels ................................................................................................ 10

Natural Science and Technology

Grade 5

Term 3

Energy and Change and Systems and Control

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Topic 10: Stored energy in fuels

Unit: 1 Fuels

Vocabulary

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.

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.

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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.

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.

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Examples of fuels and what they are used for

FUEL USE

Petrol To run engines

Firewood Heating and cooking

Gas Heating and cooking

Paraffin Lighting, heating and cooking

Candle wax Lighting

Coal Making electricity at power stations and heating

Food Providing energy to keep our bodies moving and growing

Unit 2: Burning fuels

Vocabulary

extinguish - to put out

fire-fighters - people who are trained to put out uncontrolled fires

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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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.

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.

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Unit 3: Safety with fire

How to prevent fires

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

Vocabulary

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.

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.

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.

Never put batteries in an open fire as they can explode.

Some shops and community waste centres collect old batteries. It is taken

to be recycled or to special waste disposal sites that store dangerous

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Unit 2: Mains electricity

Vocabulary

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.

Unit 3: Safety with electricity

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.

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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.

WARNING:

THE VOLTAGE OF MAINS ELECTRICITY FROM

THE WALL SOCKET IS HIGH ENOUGH TO KILL

YOU!

Topic 12: Energy and movement

Unit 1: Stored energy

Vocabulary

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

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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 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

Vocabulary

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

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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

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.

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.

fulcrum

Did you know...?

Space travel would not have been possible

without the invention of the wheel.

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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

Long ago Today