Conduction
Movement in thermal conduction of all solids:
- Atomic/molecular lattice vibrations
- Movement of free (delocalised) electrons in metallic conductors.
Conduction is the transfer of thermal energy between substances (solids).
Thermal conduction is bad in gases and most liquids, because physical contact of neighbouring molecules interacting & vibrating against each other is needed.
There are many solids that conduct thermal energy better than thermal insulators. But some thermal conductors work better than others.
Convection
Convection is an important method of thermal energy transfer in liquids and gases.
As temperature increases from convection, the liquid/gas becomes less dense, causing it to rise. As the liquid/gas rises it cools down and becomes more dense, causing it to sink. This is known as a convection current, the movement of liquids/gases in a substance.
Radiation
Thermal radiation is infrared radiation. All objects emit this radiation.
Thermal energy transfer by thermal radiation does not require a medium.
Dull, black surfaces absorb/emit better. Shiny, white surfaces absorb/emit poorly.
For an object to be at a constant temperature it needs to transfer energy away from the object at the same rate that it receives energy.
If the rate at which it receives energy is less than the rate at which it transfers energy away from the object, temperature decreases.
The temperature of the Earth is affected by factors controlling the balance between incoming radiation and radiation emitted from the Earth's surface.
Radiation increases when: temperature increases, surface area increases.
Consequences of thermal energy transfer
Consequences of thermal energy transfer:
- Heating objects such as kitchen pans
- Heating a room by convection