2.3.2

Convection

Cambridge IGCSE Physics (0625)  · Unit 2: Thermal physics  · 4 flashcards

Convection is topic 2.3.2 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 2 — Thermal physics , alongside States of matter, Particle model and Gases and the absolute scale of temperature.  In one line: Convection is the process by which thermal energy is transferred through a fluid (liquid or gas) by the movement of the fluid itself. It occurs in liquids and gases.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 4 flashcards — 1 definition — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

State what convection is and in what type of materials it occurs

Convection is the process by which thermal energy is transferred through a fluid (liquid or gas) by the movement of the fluid itself. It occurs in liquids and gases.

What the Cambridge 0625 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Know Know that convection is an important method of thermal energy transfer in liquids and gases
  2. Explain Explain convection in liquids and gases in terms of density changes and describe experiments to illustrate convection
Definition Flip

State what convection is and in what type of materials it occurs.

Answer Flip

Convection is the process by which thermal energy is transferred through a fluid (liquid or gas) by the movement of the fluid itself. It occurs in liquids and gases.

Key Concept Flip

Explain why convection does not occur in solids. Use your knowledge of particle arrangement and movement.

Answer Flip

Convection relies on the bulk movement of particles to transfer thermal energy. In solids, particles are held in fixed positions and cannot move freely to create convection currents. The particles can only vibrate.

Key Concept Flip

Explain, in terms of density changes, how a radiator heats a room. (Assume the radiator is filled with hot water.)

Answer Flip

1. The radiator heats the air directly next to it (thermal).
2. The hot air expands, becoming less dense.
3. The less dense hot air rises (convection current).
4. Cooler, denser air sinks to take its place, creating a convection current that distributes heat throughout the room.
Explanation: Convection relies on the movement of fluids (liquids or gases) due to density differences caused by temperature variations. Hotter fluids are less dense and rise, while cooler fluids are denser and sink.

Key Concept Flip

Describe a simple laboratory experiment to demonstrate convection in a liquid, such as water. Include the equipment needed and the observations you would expect to make.

Answer Flip

Equipment: Beaker, water, potassium permanganate crystals (or dye), heat source (

Example: Bunsen burner). Procedure: Place the beaker on a heatproof mat and fill it with water. Gently drop a few crystals of potassium permanganate into the water at one side of the bottom of the beaker. Apply heat to the bottom of the beaker near the crystals. Observation: A stream of coloured water will rise from the bottom, move across the top, cool and sink at the other side, forming a convection current.

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2.3.1 Conduction 2.3.3 Radiation

Key Questions: Convection

State what convection is and in what type of materials it occurs.

Convection is the process by which thermal energy is transferred through a fluid (liquid or gas) by the movement of the fluid itself. It occurs in liquids and gases.

More topics in Unit 2 — Thermal physics

Convection sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

2.1.1 States of matter

4 flashcards
2.1.2 Particle model

16 flashcards
2.1.3 Gases and the absolute scale of temperature

6 flashcards
2.2.1 Thermal expansion of solids, liquids and gases

6 flashcards
2.2.2 Specific heat capacity

8 flashcards
2.2.3 Melting, boiling and evaporation

16 flashcards
2.3.1 Conduction

8 flashcards
2.3.3 Radiation

18 flashcards
2.3.4 Consequences of thermal energy transfer

4 flashcards

Key terms covered in this Convection deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

What convection is and in what type of materials it occurs

Related Physics guides

Long-read articles that go beyond the deck — cover the whole subject's common mistakes, high-yield content and revision pacing.

IGCSE Physics MCQ mistakes

Single-letter mistakes most often costing marks in Paper 1/2

IGCSE Physics high-yield questions

Equations and reasoning chains that come up every series

IGCSE Physics 2-week revision plan

Daily breakdown for the fortnight before exams

How to study this Convection deck

Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.