In space there are no particles present so radiant heat must rely
on a different method of energy transfer.Electromagnetic
wavescarry the radiant heat. The waves transfer energy from one place to another without the material it is travelling through moving. Heat
radiation is carried byinfra-redrays
andultra-violetrays.
What carries heat radiation from one place to another? Why is the inside of an oven painted black and not white?
… solar radiation … thermogram … ultra-violet
159Infra-red detectors are used by the emergency services to find people who are trapped, especially after an earthquake. The heat from their bodies is detected by a special camera. The camera produces a heat picture of an object called a
thermogram.
In some hot countries most of the buildings are painted white. The colour white reflects
radiation very well and this keeps buildings cooler.
In cold countries buildings are often darker in colour so that they absorb as much heat as possible.
If a leaf falls onto fresh snow, after a few days of sunshine it will have sunk into the snow. Explain how this has happened. 159 radiant heat is carried by electromagnetic waves grill element toast radiant heat
FIGURE 2:When bread is toasted under a grill the heat must
travel downwards from the grill elements on to the bread. The bread absorbs this heat energy and warms up and browns. The radiation still transfers the heat energy even though there are air particles present around it.
Complete the sentences in your exercise book. Use words from the list.
cochlea eardrum ears particles middle nerve
signal vacuum vibrate vibrating vibrations wave
All sounds are made by objects. Sound travels as a from a
source to our . The sound can travel through solids, liquids and gases
but not through a . A vacuum is where there are no present.
When they reach our ears they can make the vibrate. The of
the eardrum are then passed onto the three small bones in the ear. From
there the vibrations are detected by the causing it to . The
auditory detects the vibrations and sends a to the brain.
Noise pollution is used to describe any unwanted sound.
a Give three examples of noise pollution.
b Describe one way of reducing noise pollution.
c Our hearing can be damaged by loud sounds. What two things can we do to
prevent this happening.
Which is the most accurate statement?
a Heat and temperature are the same thing.
b Heat is how hot something is.
c Temperature is measured in joules.
d Temperature measures how hot an object is.
a What is meant by conduction?
b Give two examples of when conduction can be useful
c Convection is another way that heat can travel. What is meant by convection?
d Why does convection not happen in solids?
Practice questions
Which of the following completes this sentence? Heat transfer methods that involve particles are
a Conduction and radiation.
b Conduction, convection and radiation.
c Conduction and convection.
d Convection and radiation.
Sound travels fastest in solids because the particles are closely packed and cannot move. Explain, using ideas about particles why sound waves travel faster in liquids than they do in gases.
Explain the following statements:
a It’s usually warmer during the day when the sky is clear and not cloudy.
b A cold drink from the fridge quickly warm up if it is left in the sun.
c Athletes often wrap silver blankets around them after a race.
d Fish and chips are often wrapped in newspaper or put in cardboard boxes.
Explain why sounds become fainter as you move further away from the source. Which two statements are correct?
a High pitch sounds have low frequencies.
b Low pitch sounds have low energy.
c Frequency and pitch are different things.
d High pitch sounds have high frequencies.
e Low pitch sounds have low frequencies.
f High pitch sounds have low energy.
Explain using ideas about energy transfer, why a beaker of ice left in a room will melt and warm up, but will not get any hotter than the room it is in.
Explain using ideas about energy how a double glazed window reduces heat transfer. Why will some energy always get through?
Topic Summary
162
✩I know that sounds are made by vibrating objects. page 132
✩I know that sound becomes fainter further away from the source page 136
because energy dissipates or spreads out.
✩I know that sounds travel at different speeds in solids, liquids page 140
and gases.
✩I can give some examples of common temperatures on the Celsius scale. page 150
✩I know how to calculate the speed of sound. page 137
✩I know what an echo is and I can explain what causes it. page 137
✩I can describe how insulators can reduce heat loss. page 153
✩I can describe conduction, convection and radiation. pages 154–159
✩I know the difference between a compression and a rarefaction. page 138
✩I can give some uses of an ultrasound. page 143
✩I can use the particle model to explain conduction and convection. pages 155, 157
✩I can describe how temperature difference leads to a flow of energy. page 157
✩I can use a model ear to describe some possible causes of hearing pages 144–146
impairment.
✩I can use my ideas about heat transfer to explain the use of conductors pages 153–154
and insulators in a range of situations.
✩I can use my ideas about energy to explain heat transfer by radiation. page 158
✩I can explain using ideas about energy transfer, the dissipation of pages 136–159
1 What is the common unit of temperature?
2 What is room temperature?
3 What is the boiling point of water?
4 What is the difference between heat
and temperature?
5 What is an insulator?
6 Why is the inside of an oven painted
black?
7 What causes a sound?
8 How can a guitar produce a higher
note?
9 What is the range of human hearing?
10 Why can sound not travel through a
vacuum?
11 What are the units of frequency? 12 Why do sounds become quiet further
away from their source?
13 What is ultrasound? Give an example
of its use.
True or False?
If a statement is false then rewrite it so it is correct.
1 Heat travels in solids by convection. 2 Energy from the Sun reaches us by
conduction.
3 Heat energy flows from hotter places to
cooler places.
4 Dark surfaces are good at reflecting heat
energy.
5 Double glazing works by preventing
conduction and radiation.
6 Sound travels fastest in liquids. 7 Sound can travel through a vacuum. 8 Pitch and frequency are the same thing. 9 Ultrasound is used for cooking.
10 A compression is a low pressure where
the particles are spread out.
11 Loud sounds have a larger amplitude
than quiet sounds.
12 The ear drum is the only part of the ear
that vibrates.
Literacy Activity
Write an article about saving heat energy at home.
You should explain what methods you could use, why they work and why you need to do it. You could choose to do this as
An article in a local newspaper For pupils in a primary school
As a poem As a leaflet for local people
As a poster for display in your school
Write a letter to a newspaper about noise pollution. You need to explain some of the concerns that people have about their exposure to noise pollution. You should also consider some possible solutions and decide if these are useful or not.
Topic Quiz
163
ICT Activity
Make a short powerpoint presentation to teach year 5 and 6 pupils some of the key facts about sound that they should know.
A cock robin has been found dead – but how did it die? It is 15 times more likely that the robin was killed by a domestic cat than a sparrow hawk or owl. If the robin has shed feathers, it might have died from a fungal infection. It is also possible that it was a road casualty or died defending its territory from another male robin.
The male robin is a very aggressive animal and has been found to swoop on and viciously peck red dummy birds left in its territory. Robin numbers are in decline and in very cold winters they are likely to
die from the cold or starvation if they cannot get enough food. On a cold night a robin can lose up to 10% of its body weight and will need to replenish its reserves within two days. Putting food out on a bird table in the winter can help the robin survive. So what else do we know about the robin?
Breeding
The male robin starts courtship at the end of January and breeds in March when he has established a territory. The territory is about 0.5 hectares (six territories would fit into a football pitch). A robin nest is cup-shaped and is made from dead leaves, grass, hair and mosses. It can be found in hedges, walls, holes in trees and even garden sheds. The robin lays about four to six eggs in a clutch and they are incubated over the next 13 days. Usually two clutches are produced in a year, although in good conditions four can be produced. The robin starts to reproduce after one year.
By the end of this unit you’ll be able to explain how energy is transferred in
food webs, how the resources in a habitat affect the numbers and how
habitats change. You’ll be able to explain the applications and
implications of these ideas. BIG IDEAS
BIG IDEAS
164