P1a 1 - Heat transfer

Thermal radiation - energy transfer by electromagnetic waves

Dark matt surfaces - best absorbers/emitters of thermal radiation

Big surface area - more waves emitted - more heat given off - fast heat transfer

Heat conduction - vibrating particles pass on their energy to others

1. A metal rod is heated and the free electrons at one end move faster
2. The free electrons diffuse and collide with electrons at the cooler end of the rod
3. Their kinetic energy is transferred to the other electrons

Nonmetals - bad conductors because they have no free electrons

Heat convection - energetic particles move from a hot area to a cold area and take their heat energy with them

1. Fluids and gases rise when heated because they become less dense
2. They fall as they cool down again and become more dense
3. Convection currents transfer heat energy from hotter places to cool places.

Convection only takes place in liquids and gases