What is conduction?
The transfer of thermal energy through a material when particles vibrate and pass energy to neighbouring particles.
Which materials are the best conductors?
Metals — because they have free electrons that transfer energy quickly.
What is convection?
The transfer of heat in fluids (liquids and gases) caused by warm, less dense fluid rising and cooler, denser fluid sinking.
Describe a convection current.
Warm fluid rises → cools and becomes denser → sinks → cycle repeats, transferring heat.
What is infrared radiation?
Electromagnetic waves that transfer heat energy without particles or direct contact.
What surfaces are best at absorbing infrared radiation?
Dark, matte (dull) surfaces.
What surfaces are best at reflecting infrared radiation?
Light, shiny surfaces.
What is thermal conductivity?
A measure of how well a material conducts heat. High thermal conductivity = faster heat transfer.
How do insulation materials reduce heat transfer?
They trap air (a poor conductor), reducing conduction and convection.
Give examples of home insulation.
Cavity wall insulation, loft insulation, double glazing, draught-proofing.
How does double glazing reduce heat loss?
Two glass layers with air or vacuum between them reduce conduction and convection.
Why does a vacuum stop heat transfer?
There are no particles — so no conduction or convection can occur.
What is specific heat capacity?
The amount of energy needed to raise 1 kg of a substance by 1°C.
State the equation for specific heat capacity.
ΔE = m × c × Δθ
Energy = mass × specific heat capacity × temperature change.
What is thermal insulation?
Any material that slows the transfer of heat energy.
How can you reduce unwanted energy transfer in houses?
Increase insulation, use thicker walls, use materials with low thermal conductivity.
What is the role of free electrons in metal conduction?
They move freely and transfer energy quickly, making metals good conductors.
Why does warm air rise?
It expands, becomes less dense, and moves upward above cooler, denser air.
What is black-body radiation?
Radiation emitted by a perfect absorber and emitter; hotter objects emit more radiation.
What happens to infrared emission as an object’s temperature increases?
It increases — hotter objects emit more infrared radiation.
What factors affect the rate of thermal conduction?
Thermal conductivity, temperature difference, thickness of material, surface area.
Why does a larger temperature difference increase heat transfer?
Energy flows faster from a hot region to a cold region.
What is the role of air in insulating materials?
Air is a poor conductor and reduces convection when trapped in small pockets.
How does loft insulation reduce convection?
It traps layers of air in fibrous material, preventing convection currents.
