Thermal equilibrium
Cambridge A-Level Physics (9702) · Unit 14: Temperature · 6 flashcards
Thermal equilibrium is topic 14.1 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 14 — Temperature , alongside Temperature scales and Specific heat capacity and specific latent heat. In one line: Thermal energy is the energy a substance possesses due to the kinetic energy of its particles. The greater the substance's temperature, the greater the thermal energy.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 6 flashcards — 2 definitions and 3 key concepts — covering the precise wording mark schemes reward. Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Thermal energy
Thermal energy is the energy a substance possesses due to the kinetic energy of its particles. The greater the substance's temperature, the greater the thermal energy.
What the Cambridge 9702 syllabus says
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- understand that (thermal) energy is transferred from a region of higher temperature to a region of lower temperature
- understand that regions of equal temperature are in thermal equilibrium
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in Thermal equilibrium
- › Focus purely on the physical distance between particles; compare the relative increase in spacing during melting versus the much larger increase during boiling.
- › Ensure both the resultant force and the resultant moment are zero for a system to be in equilibrium.
What is thermal energy?
Thermal energy is the energy a substance possesses due to the kinetic energy of its particles. The greater the substance's temperature, the greater the thermal energy.
In what direction is thermal energy transferred?
Thermal energy is always transferred from a region of higher temperature to a region of lower temperature. This transfer continues until thermal equilibrium is reached.
What does it mean for two regions to be in thermal equilibrium?
Two regions are in thermal equilibrium when they are at the same temperature and there is no net transfer of thermal energy between them. Both regions have reached a stable state.
Describe, at a microscopic level, what happens when two objects at different temperatures are brought into contact.
The particles in the hotter object have, on average, greater kinetic energy. Collisions between these particles and the slower-moving particles of the cooler object result in a transfer of kinetic energy, thus increasing the temperature of the cooler object and decreasing the temperature of the hotter object.
Give an example of a system reaching thermal equilibrium.
A cup of hot coffee left on a table will gradually cool down until it reaches thermal equilibrium with the surrounding room temperature. At this point, the coffee's temperature will no longer decrease.
How does the rate of thermal energy transfer change as the temperature difference between two regions decreases?
The rate of thermal energy transfer decreases as the temperature difference decreases. The greater the temperature difference, the faster the transfer; the smaller the temperature difference, the slower the transfer.
Review the material
Read full revision notes on Thermal equilibrium — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 14 — Temperature
Thermal equilibrium sits alongside these A-Level Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Thermal equilibrium 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.
How to study this Thermal equilibrium deck
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