Physics · KS3 and GCSE · Interactive lesson
Conduction, convection and radiation
Explore how energy travels through solids, moving fluids and empty space. Compare materials, heater positions and surfaces with clear visual models.
Choose your view
Explore an interactive example, then try the questions at your own pace.
KS3 / GCSE · start with the idea
By the end of this lesson: Explain how energy passes from a hotter region to a cooler one.
The interactive diagram and controls are in Stage 2, “Explore one example”. Read the idea here, then try it next.
- When one end of a solid is warmed, its particles vibrate more vigorously.
- Particles pass energy to neighbouring particles. They stay around their fixed positions.
- Metals usually conduct energy much more quickly than dry wood under the same conditions.
Useful starting points
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What do the words mean?
- Conduction
- Energy transferred through a material by interactions between its particles. Free electrons also transfer energy in metals.
- Convection
- Energy transferred by the bulk movement of a liquid or gas.
- Thermal radiation
- Energy carried by electromagnetic waves, including infrared. It can travel through a vacuum.
- Overall transfer
- The overall transfer after transfers in opposite directions are compared.
- Insulator
- A material that reduces a particular way of transferring energy. It does not stop every energy transfer.
Change the example
This is the lesson example. Your practice question uses its own numbers.
Something to try
Keep the temperature difference the same. Compare metal and wood, then work through the explanation steps. Which transfers energy faster?
Notice what changes
How particle motion works +
Starts paused. Press Play, then add energy to see the warmer particles move faster.
Particles keep the same size. Liquid particles move around; solid particles vibrate around fixed positions. This is a simplified model, with the change in motion exaggerated to make it easier to see.
About the playback +
About this model
Step 1 of 3: The left end is warmer: 40 °C compared with 20 °C. Its particles vibrate more vigorously on average. The arrows show the direction of energy transfer, not moving solid particles. This is an explanation in three parts, not a timed simulation. Arrow sizes do not measure transfer rates. The material comparison keeps the bar dimensions and end temperatures the same.
More about this diagram
Still picture. Play particle motion in Stage 2.
Aluminium conducts faster than dry wood: 40 °C → 20 °C
Still picture of the example from Stage 2. Use the back arrow to change it.
Work through it
Starting example: read the steps below
- The left end is warmer: 40 °C compared with 20 °C. Its particles vibrate more vigorously on average.
- Aluminium conducts energy more quickly than an equal-sized dry wooden bar with the same temperature difference.
- To compare the materials fairly, keep the bar length, thickness and temperature difference the same.
- A larger temperature difference usually increases the rate of conduction if the other conditions stay the same. No rate is calculated here.
Try on your own
Your turn. No rush.
Question 1
One end of a solid metal spoon is in hot soup. Why can its handle become warm?
About these questions
Questions appear in a mixed order. Work at your own pace and stop whenever you like.
These questions use their own numbers, separate from the lesson example. You can stop whenever you like. Answers last for this visit to the page.
A good place to pause
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Why can energy travel along a solid bar even though the solid particles do not travel from one end to the other?
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Notes for parents and tutors
These lessons cover selected KS3 and GCSE ideas for England; they are not a complete course. The level notes explain where GCSE methods or optional extensions begin. Maurice can help you choose material for your course and exam board.
The content draws on the DfE Maths curriculum, DfE Science curriculum and AQA GCSE Physics specification. Level labels are guidance, not exam-board endorsements. For AQA Radioactivity, calculating net decline as a ratio is Higher-tier work. Net means the overall change; ask Maurice whether this extension is relevant to your course. Explanations and practice were reviewed during development on 21 October 2026; Maurice should check their fit before assigning work.
Topic labels and your lesson-view preference are saved in this browser. This tab also remembers the last lesson stage, so you can choose to continue there. If you choose revision, selected activities and suggested revisit dates are saved here too. Recent question codes are also kept to reduce repeats. Reflection notes are saved automatically per topic when you type them; you can delete a note in the recap. They stay in this browser and are visible to other people using it. Practice answers and enquiry details are not saved. Clearing browser data removes the labels.