Heating & Cooling
Year 8 🌡️ Energy & Thermodynamics Describe conduction, convection and radiation in detail.
🔥 Conduction
Conduction is heat transfer through a material without the material itself moving. Particles vibrate and pass energy to their neighbours.
| 🔬 Material | ♨️ Conductor? | 📝 Why |
|---|---|---|
| Metals (copper, iron) | ✅ Good conductors | Free electrons carry energy quickly |
| Wood, plastic, rubber | ❌ Poor conductors (insulators) | No free electrons; particles move slowly |
| Air | ❌ Very poor conductor | Particles are far apart |
| Wool, fibreglass | ❌ Good insulators | Trap pockets of air |
🍳 Frying pan: Metal base conducts heat from flame to food. Plastic handle is an insulator — it stays cool to touch!
🌊 Convection
Convection transfers heat through fluids (liquids and gases) by the movement of the fluid itself.
🌊 How Convection Works
Hot fluid → less dense → rises ↑
Cool fluid → more dense → sinks ↓
→ Creates a convection current 🔄
🌡️ Radiator: Hot air rises from the radiator, cool air moves in to replace it → room air circulates and heats up.
🌊 Sea breezes: Daytime — land heats faster than sea → warm air over land rises → cool sea air moves in = sea breeze. Perfect for surfing! 🏄
☀️ Radiation (Infrared)
Radiation is heat transfer by infrared (IR) electromagnetic waves. It does NOT need a medium — it can travel through a vacuum!
| 🎨 Surface type | Absorber | Emitter |
|---|---|---|
| Dark, matt (black) | ✅ Best absorber | ✅ Best emitter |
| Light, shiny (silver/white) | ❌ Poor absorber | ❌ Poor emitter |
☀️ Sun → Earth: The Sun's energy travels 150 million km through the vacuum of space as infrared radiation — reaching us in just 8 minutes!
Houses in hot countries are painted white to reflect sunlight and stay cool. Solar panels are black to absorb as much radiation as possible!
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
🌡️ Heat Transfer Explorer