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SMART-EXAM-RESOURCES
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At the end of a long race, an athlete may be wrapped in a shiny foil blanket to
prevent him cooling down too quickly.
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CAMBRIDGE LOWER SECONDARY CHECKPOINT
PRACTICE QUESTIONS AND MARK SCHEMES
Subject: Physics TOPIC: Energy
Set-3
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Explain how the shiny foil blanket helps to reduce energy losses. Use ideas about
conduction, convection and radiation in your answer.
[3]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 1
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MARK SCHEME:
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shiny foil traps layer of air around body, stops convection ;
air is a good insulator / poor conductor ;
shiny foil is a poor radiator of heat ;
shiny foil reflects radiation back ;
heat can still escape by conduction ; [max 3]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 2
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Energy travels to the Earth from the Sun.
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State whether this transfer of energy is by conduction, convection or radiation.
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Explain your answer.
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[2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 3
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MARKING SCHEME:
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radiation ;
(only) radiation can travel through vacuum/ conduction and convection need
medium ; [2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 4
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(a) Fig. 3.1 shows a potato being baked in the oven of an electric cooker.
potato
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metal skewer
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heating element
Fig. 3.1
The potato has a metal skewer (a long metal pin) pushed through it.
(i)
The air in the oven is heated by the heating element.
On Fig. 3.1 draw an arrow to show how the heated air moves inside the oven.
(ii)
[1]
Name the main method of thermal energy transfer in the heated air.
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(iii)
The metal skewer transfers heat to the inside of the potato by conduction.
Describe the process of conduction in a solid, using ideas about particle vibration.
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Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 5
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MARKING SCHEME:
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(a)(i) arrow showing heated air rising ; [1'
(a)(ii) convection ; [1]
(a)(iii) particles vibrate more / gain energy ;
this vibration is passed through metal ;
[2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 6
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Fig. 3.2 shows an iron rod being heated at one end by a Bunsen burner.
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Fig. 3.2
Thermal energy passes through the rod by conduction.
(i)
Describe the process of conduction in solid iron, using ideas about the vibration of atoms.
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..................................................................................................................................... [2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 7
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MARKING SCHEME:
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(incident energy / energy gained, makes) atoms vibrate more ;
this vibration is passed through metal ;
[2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 8
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Fig. 8.1 shows the inside of a refrigerator.
freezing
compartment
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Fig. 8.1
(a) The air inside the refrigerator is cooled by convection.
The cold air moves downwards from the freezing compartment and displaces warm air which
moves upwards.
Explain this movement in terms of particles.
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Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 9
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MARKING SCHEME:
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(a) particles move more slowly / have less energy ;
particles become closer together ;
gas becomes more dense ; [max 2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 10
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Use the idea of convection to explain why a kettle has the heating element at the
bottom.
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[2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 11
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MARKING SCHEME:
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hot water rises/ cold water sinks ;
(because) hot water is less dense/ cold water is more dense ; [2]
Cambridge Lower Secondary Checkpoints
Stage 9 Practice Questions Physics
Smart Exam Resources 12