Heat transfers

Question 1

Describe how conduction occurs

Answer 1

Vibrating particles transfer energy from their kinetic energy store to the kinetic energy stores of neighbouring particles as they collide, causing a rise in temperature

Question 2

Describe how convection occurs

Answer 2

Energy is transferred from heater within liquid/gas to thermal energy store of water/gas by conduction. Particles near the heater gain more kinetic energy, meaning liquid/gas expands and becomes less dense. These hotter particles rise above denser, cooler liquid/gas.

Question 3

How to reduce conduction?

Answer 3

Use materials with low thermal conductivity/use insulators

Question 4

How to reduce convection?

Answer 4

Create pockets of trapped air. Air can’t move so energy has to conduct very slowly through pockets of air and material between them.

Question 5

Which colour substances emit IR radiation and which colour doesn’t

Answer 5

Black, dull surfaces are good emitters
Silver, shiny surfaces are poor emitters

Question 6

Which colour absorbs IR radiation and which reflects?

Answer 6

Black absorbs radiation
Silver reflects radiation