This topic summary covers Knowledge Organiser: Heat Transfer within Heat Transfer for GCSE Physics. Revise Heat Transfer in Energy for GCSE Physics with 14 exam-style questions and 11 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 17 of 17 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Heat Transfer
Key Terms
- Conduction: particle vibrations transfer energy (solids/metals)
- Convection: fluid movement transfers energy (fluids only)
- Radiation: infrared waves transfer energy (all media + vacuum)
- Free electrons: responsible for metal's high conductivity
Key Facts
- Conduction: particles don't move, only vibrate
- Convection: hot fluid rises (less dense), cool sinks
- Radiation: works in vacuum; black surfaces best absorbers/emitters
- Metals conduct well due to free electrons
What Works Where
- Solids: conduction only
- Fluids: convection (and conduction)
- Vacuum: radiation only
- Thermos flask: vacuum blocks conduction + convection; silvered walls reduce radiation
Exam Tips
- Convection needs density change — mention this in explanations
- Metals: free electrons make them better conductors
- Black surfaces: best absorbers AND best emitters
- Trapped air = good insulator (poor conduction, no convection)
Key Equations
- ΔE = m × c × ΔT (thermal energy change)
- Rate of transfer ∝ surface area (larger area → faster transfer)
- Rate of transfer ∝ temperature difference (bigger ΔT → faster transfer)
- Efficiency = useful energy out ÷ total energy in × 100%
Common Mistakes
- Saying convection occurs in solids: Convection requires a fluid (liquid or gas) — particles in solids cannot move freely to form currents
- Forgetting density change in convection explanations: Must state that hot fluid expands, becomes less dense, and rises — not just "hot air rises"
- Confusing black and shiny surfaces: Black/matt surfaces are best emitters AND absorbers; shiny/silver surfaces are poor emitters AND poor absorbers
- Saying radiation needs a medium: Infrared radiation travels through a vacuum — it does not need particles
- Confusing insulation with zero transfer: Insulation slows heat transfer — it does not stop it completely
Practice questions for Heat Transfer
Which method of thermal energy transfer occurs mainly in solids?
Explain how a convection current forms when the base of a fluid is heated.
Quick recall flashcards
Examples
wood, plastic, glass, air, wool
Fluid is heated
particles gain kinetic energy → move faster → spread out