SEC G3 Combined Science Physics component K326/K327
CP8: Thermal Processes
Explain conduction, convection, radiation, and the dominant transfer path in context.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Heating transfers energy from higher temperature to lower temperature until no temperature difference remains.
Direction and thermal equilibrium
A temperature difference sets the direction of energy transfer by heating. Transfer continues from the hotter region to the cooler region until both reach the same temperature.
At thermal equilibrium there is no net energy transfer by heating between the regions, although particles continue moving microscopically.
Conduction and convection
In solids, neighbouring particles pass energy through increased vibration. In metals, mobile electrons also carry energy rapidly through the structure.
In fluids, heating can reduce density so warmer material rises while cooler, denser material sinks. This circulation transfers energy by convection.
Radiation and applications
Thermal radiation is electromagnetic and needs no material medium. Transfer rate depends on surface colour and texture, surface temperature, and surface area.
Apply all three mechanisms to real systems. A metal pan conducts, moving water convects, and a hot surface radiates, while insulation is chosen to reduce the relevant pathways.
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: Why does a dull black cooling surface lose energy faster than a shiny surface of the same area and temperature?
- The transfer mechanism is infrared radiation.
- Surface colour and texture affect emission rate.
- A dull black surface is a better emitter than a shiny surface.
Answer: It emits thermal radiation at a greater rate under the same conditions.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Identify conduction, convection, and radiation as different transfer mechanisms.
- Explain the dominant pathway using particles, bulk fluid motion, or electromagnetic radiation.
- Apply surface colour, texture, temperature, and area only where they affect thermal radiation.
Official outcome coverage
K326 CP8: 5 mapped outcomes, references CP8(a), CP8(b), CP8(c), CP8(d), CP8(e). Check the official K326 syllabus.
K327 CP8: 5 mapped outcomes, references CP8(a), CP8(b), CP8(c), CP8(d), CP8(e). Check the official K327 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Investigate a factor affecting thermal transfer, such as insulation or surface finish. Use equal starting temperatures and sample quantities, measure at fixed times, repeat where feasible, and evaluate whether heat exchange with the room or uneven sensor placement limits the comparison.
Exam traps and retrieval check
Avoid these traps
- Saying cold flows into a hot object.
- Explaining convection without a density change.
- Claiming radiation requires air.
Check from memory
When is thermal equilibrium reached?
When the regions have the same temperature and no net heating transfer occurs.
Why do metals conduct well?
Particle vibrations and mobile electrons transfer energy.
Which thermal process works through vacuum?
Radiation.
Official Combined Science scope
This shared Combined Physics owner serves both K326 and K327. Thermal equilibrium, conduction, convection, radiation, and applications of the three transfer processes.