IGCSE Physics Conduction Questions and Worked Solutions (2.3.1) | 0625

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IGCSE Physics 0625 · Topic 2.3.1

IGCSE Physics Conduction Questions and Worked Solutions

50 topic-wise practice questions on Conduction (Unit 2: Thermal Physics), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions19 Core21 Extended10 Challenge121 marksTextbook §2.3 · pp. 115–126
Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: Conduction

Conduction transfers thermal energy through a material without the material moving. Metals are good conductors; non-metals and gases are poor conductors (insulators).

Key formulas

No equations to learn in this subtopic — compare conductors qualitatively.

Prerequisite knowledge

  • Particle model (2.1.2)
  • Internal energy (2.2.2)

Exam tips & common mistakes

  • Trapped air is an insulator because it conducts poorly AND cannot form convection currents
  • Metal feels colder than wood at the same temperature because it conducts energy away from your hand faster
  • Name 'free electrons' and 'lattice vibrations' for Extended marks

Key facts from the syllabus (2.3.1)

  • Good thermal conductors: metals (e.g. copper, aluminium); poor conductors: plastics, wood, glass, air
  • Experiment: rods of different metals with wax and pins, heated at one end — pins fall first from the best conductor
  • Water is a poor conductor (ice at the bottom of a tube stays solid while water at the top boils)
  • Extended in all solids, energy passes by lattice vibrations between neighbouring particles
  • Extended metals also conduct by free (delocalised) electrons, which is why they are much better conductors
  • Extended gases and liquids are poor conductors because particles are far apart / not in a lattice

Textbook: §2.3 Transfer of thermal energy, pp. 115–126

1
Core[3 marks]

Describe an experiment to compare how well different metals conduct thermal energy.

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Method: Rods with wax, heat one end.

Attach drawing pins with wax along equal rods of different metals; heat one end of each equally; the pins fall off first on the best conductor
2
Core[1 mark]

Give one example of a good thermal conductor.

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Method: Metals.

e.g. copper (any metal)
3
Core[1 mark]

Give one example of a poor thermal conductor (insulator).

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Method: Non-metals.

e.g. wood, plastic, air
4
Core[2 marks]

Explain why saucepans are made of metal but have plastic handles.

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Method: Metal conducts; plastic insulates.

Metal conducts thermal energy to food quickly; the plastic handle is an insulator so it stays cool
5
Core[2 marks]

A metal bench and a wooden bench are at the same temperature on a cold day. Explain why the metal feels colder.

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Method: Metal conducts energy from the hand faster.

Metal conducts energy away from your hand faster than wood
6
Core[2 marks]

Describe an experiment to show that water is a poor conductor of thermal energy.

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Method: Ice weighted at bottom, heat top.

Weight ice at the bottom of a tube of water and heat the top; water at the top boils while the ice stays unmelted
7
Core[2 marks]

State two factors that affect the rate of conduction through a rod.

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Method: Material, length, area, temperature difference.

e.g. the material, its thickness (cross-sectional area), its length, the temperature difference
8
Core[2 marks]

Explain why cooking pots often have copper bases.

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Method: Copper is an excellent conductor.

Copper conducts thermal energy quickly and evenly to the food
9
Core[2 marks]

Explain why birds fluff up their feathers in cold weather.

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Method: Trap air.

To trap more air, which is a poor conductor, reducing energy loss
10
Core[2 marks]

State what is meant by thermal conduction.

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Method: Transfer through material.

Transfer of thermal energy through a material without the material itself moving
11
Core[2 marks]

Rank copper, glass and air in order of thermal conductivity from best to worst.

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Method: Metals best.

Copper, glass, air
12
Core[2 marks]

Explain why tiles feel colder than carpet to bare feet at the same temperature.

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Method: Conductivity.

Tiles are better conductors, so they transfer energy away from your feet faster
13
Core[2 marks]

Explain why ice boxes have thick plastic walls.

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Method: Insulation.

Plastic (and trapped air/foam) is a poor conductor, reducing energy transfer into the box
14
Core[3 marks]

Describe how to show that copper is a better conductor than iron using rods, wax and a Bunsen burner.

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Method: Wax melts further.

Coat equal rods with wax; heat one end of each equally; the wax melts further/faster along the copper rod
15
Core[2 marks]

State two variables that must be kept the same when comparing the conductivity of rods.

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Method: Fair test.

Length and diameter of the rods; heating rate/temperature of the heat source
16
Core[2 marks]

Explain why a metal pan with a wooden handle is safe to hold.

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Method: Wood insulator.

Wood is a poor conductor so the handle does not get hot
17
Core[2 marks]

Explain why animals that live in cold places often have thick fur.

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Method: Traps air.

The fur traps air, a poor conductor, reducing energy loss
18
Core[2 marks]

Explain why a string vest can keep you warm.

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Method: Traps air.

It traps a layer of air next to the skin
19
Core[2 marks]

State why a vacuum does not conduct thermal energy.

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Method: No particles.

There are no particles to pass on energy
20
Extended[3 marks]

Explain how thermal energy is conducted through a non-metal solid.

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Method: Lattice vibrations passed on.

Particles at the hot end vibrate more and pass vibrations to neighbouring particles through the lattice
21
Extended[3 marks]

Explain why metals are better thermal conductors than non-metals.

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Method: Free (delocalised) electrons.

Metals have free (delocalised) electrons that move quickly and transfer energy through the metal, as well as lattice vibrations
22
Extended[3 marks]

Explain how thermal energy is conducted through the copper base of a pan.

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Method: Free electrons gain KE and travel; lattice vibrations.

Particles at the hot side vibrate more; free electrons gain kinetic energy, travel through the copper and collide with particles, transferring energy
23
Extended[2 marks]

Explain, in terms of particles, why gases are poor conductors of thermal energy.

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Method: Particles far apart.

Particles are far apart, so collisions that transfer energy are infrequent
24
Extended[2 marks]

Explain why most liquids are poor thermal conductors.

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Method: Particles not in a lattice; no free electrons.

Particles are not fixed in a lattice and there are no free electrons, so energy is passed on slowly
25
Extended[2 marks]

Explain why trapped air is a good insulator.

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Method: Poor conductor; trapped so no convection.

Air conducts poorly and, when trapped, cannot transfer energy by convection
26
Extended[1 mark]

Name a material that conducts thermal energy better than an insulator but less well than a metal.

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Method: Intermediate conductors.

e.g. glass or brick (or concrete)
27
Extended[3 marks]

Explain why there is a much greater rate of energy transfer through a metal pan than through its wooden handle.

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Method: Free electrons in metal.

Metal has free electrons that carry energy rapidly; wood has only lattice vibrations, which transfer energy slowly
28
Extended[2 marks]

Explain why a woolly jumper keeps you warm.

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Method: Traps air.

It traps air, which is a poor conductor, reducing energy transfer from the body
29
Extended[2 marks]

Explain why double-glazed windows reduce energy loss.

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Method: Gap of air/vacuum.

The gap between panes contains air (or a vacuum), which conducts poorly
30
Extended[2 marks]

Explain why a metal spoon in hot tea becomes hot along its whole length.

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Method: Conduction by free electrons and vibrations.

Energy is conducted from the hot end by free electrons and lattice vibrations to the cooler end
31
Extended[3 marks]

Describe the two mechanisms of thermal conduction in metals.

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Method: Lattice vibrations and free electrons.

Lattice vibrations passed between neighbouring atoms, and free electrons moving through the metal carrying energy
32
Extended[2 marks]

Explain why free electrons transfer energy much faster than lattice vibrations.

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Method: Move quickly and far.

They move fast and travel long distances before colliding, carrying energy rapidly
33
Extended[2 marks]

Explain why non-metal solids conduct thermal energy only slowly.

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Method: Only lattice vibrations.

They have no free electrons, so energy is passed only by lattice vibrations
34
Extended[2 marks]

Explain why a gas is a poorer conductor than a solid.

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Method: Particles far apart.

Particles are far apart, so collisions that pass on energy are less frequent
35
Extended[3 marks]

Explain why a metal object at 0 °C feels colder than a plastic one at 0 °C.

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Method: Rate of conduction.

Metal conducts energy away from the hand much faster due to free electrons, so the hand cools faster
36
Extended[2 marks]

Explain why wet clothes make you feel colder than dry clothes in the cold.

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Method: Water conducts better than air.

Water conducts better than trapped air, so energy is lost faster (also evaporation)
37
Extended[2 marks]

State why snow can act as an insulator for plants.

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Method: Trapped air.

Snow contains trapped air, a poor conductor
38
Extended[2 marks]

Explain why the bottom of a cooking pan is often thicker than the sides.

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Method: Spread energy evenly.

A thick conducting base spreads the energy evenly, preventing hot spots
39
Extended[2 marks]

A metal rod is heated at one end. Explain why the far end eventually warms up.

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Method: Conduction.

Energy is passed along by free electrons and lattice vibrations from the hot end to the cold end
40
Extended[2 marks]

Explain why a thick layer of insulation reduces energy loss more than a thin layer.

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Method: Longer path.

Energy has to be conducted through a greater thickness, so the rate of transfer is lower

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

41
ChallengeCore[4 marks]

Describe a fair experiment to rank copper, aluminium and steel as thermal conductors, stating the variables to control.

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Method: Wax and pins.

Equal-length, equal-diameter rods with pins fixed by wax at equal distances; heat the ends equally (same flame position); time how long until the pins fall; control length, diameter, heating and starting temperature
42
ChallengeCore[3 marks]

Explain why a metal tray from a hot oven burns your hand faster than a wooden board at the same temperature.

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Method: Conduction rate.

Metal conducts energy to your hand much faster
43
ChallengeCore[3 marks]

Explain why loft insulation uses materials containing trapped air.

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Method: Air poor conductor.

Air is a poor conductor and trapping it prevents convection
44
ChallengeExtended[4 marks]

Explain why metals conduct thermal energy by two mechanisms and non-metals by only one.

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Method: Free electrons.

Both have lattice vibrations; metals also have free electrons that carry energy quickly through the structure
45
ChallengeExtended[4 marks]

Explain why a metal spoon in hot soup becomes hot along its length faster than a plastic spoon, using particles and electrons.

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Method: Electrons transfer energy.

Free electrons in the metal gain kinetic energy at the hot end and move rapidly, colliding with ions further along; plastic relies only on slow lattice vibrations
46
ChallengeExtended[3 marks]

Explain why gases are very poor thermal conductors in terms of particle spacing.

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Method: Infrequent collisions.

Particles are far apart, so energy-transferring collisions are rare
47
ChallengeExtended[4 marks]

Two rods of the same material are heated at one end. Rod A is twice as thick as rod B. Predict which conducts energy along it at a greater rate and explain.

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Method: Area.

Rod A: a larger cross-sectional area provides more paths for energy transfer
48
ChallengeExtended[4 marks]

Explain why water is a poor conductor using the experiment where ice weighted at the bottom of a tube stays solid while water at the top boils.

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Method: Conduction slow, no convection downward.

Energy must travel down by conduction (hot water stays at the top), and water conducts so poorly that the ice does not melt
49
ChallengeExtended[4 marks]

A builder can use bricks or aerated blocks (full of tiny air pockets) for a house wall. Explain which gives better insulation.

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Method: Trapped air.

Aerated blocks: trapped air pockets conduct poorly, reducing energy transfer by conduction
50
ChallengeExtended[3 marks]

Explain why an object in contact with a better conductor feels colder even when both are at the same temperature.

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Method: Rate of energy transfer.

Energy flows from the hand faster into the better conductor, so the hand cools faster
All IGCSE Physics topics← 2.2.3 Melting, Boiling and Evaporation2.3.2 Convection →

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