Energy Grade 7

Heat energy

Two main sources of energy

Non-renewable sources:

Fossil fuels1. Wood2. Coal3. Oil4. GasDescription: Will not be available for ever we are running short of these resources

Renewable sources

Nature provide these

1. Sun2. Wind3. Water

Description:Will be in nature at all times but in different quantities at times.

FOS

SIL FU

ELS They are made from the remains of plants and animals that died

many millions of years ago.

HEAT E

NER

GY

Wh

at is

heat

Wh

at is

tem

pera

ture

Objects feel hot or cold because they contain heat Hot objects contain more heat Cold objects contain less heat This is an indication of the amount of energy that an

object has. More heat means more energy, which indicates that

the particles are moving faster Heat causes the temperature of an object to rise

We can measure the heat with a thermometer. The temperature is then indicated in 0C or 0F The 0C is the unit we use to indicate the heat the

object has This is a method of measuring the energy that object

has or the ability of the particles to move around

What happens to the temperature of water when we heat it on a stove?

Tran

sfe

r of h

eat e

nerg

y

Con

du

ctio

n

Happens in a solid Particles at warm end has more energy Particles at cold end has less energy Energy is transferred from warm particles to

the cold particle Can be explained with metal rod in burning

candle

Tran

sfe

r of h

eat e

nerg

y

Con

vectio

n

Happens in a liquid or a gas Particles at warm end rises Particles at cold end decent Energy is transferred from warm particles to

the cold particle Can be explained with coloured water in glass

beaker on burner This causes convection currents and

convection rain

Tran

sfe

r of h

eat e

nerg

y

Rad

iatio

n

Happens in a medium without contact

Heat from the sun takes 8 minutes to reach earth after traveling 150 million km

Heat travels in the form of waves The heat will be absorbed by conductors Heat will not be absorbed by insulators This causes the inside of a car to heat up in

the sun

Revision page

1. Give one word for the following:1.1.contains nutrients to make the plants grow better.1.2. formed under ground or under the sea million of years

ago from buried plants and animals.1.3.an instrument for measuring temperature

2. Explain the difference between:2.1.renewable and non-renewable energy sources2.2.heat and temperature2.3.conduction and convection2.4.conductors and insulators

3. Report in your group on the following issue:The burning of fossil fuels and the impact it has on the environment

Brain-Teasers

1. How does the use of electricity pollutes the environment?

2. What happens to our marine life when there is an oil spill?

3. Why do some scientist concider nuclear energy to be safe and others not?

4. What does it mean to be energy-efficient? Would you say that South Africa is energy-efficient? Give reasons.

5. Why do we not have any hydro-electric power plants in South Africa?