Heat always travels from a higher temperature to a lower temperature.
	Heat travels in three ways: Conduction, Convection and Radiation.

 

Def: Conduction is the movement of heat through a substance without any movement of the substance.

 

The heat travels from one particle to the next, but the particles themselves don’t move.

 

Def: A conductor is a substance, which lets heat through it easily. (e.g. Metal)

 

Def: An insulator is a substance, which doesn’t let heat pass through it easily.

 

	Metals = Good Conductor
	Non-Metals = Bad Conductors
	Most Liquids are poor conductors of heat.

Gases are poor conductors of heat. (e.g. air)

 

Def: Convection means that heat is carried through liquids and gases by the movement of particles. 

Def: Heat radiation means that heat travels in invisible rays without needing a substance to travel through.

 

	Unlike conduction and convection, radiated heat can travel through a vacuum.
	Dark surfaces are better at radiating (giving off) and absorbing heat than bright substances.

 

Air is a good insulator, which is why loose woollen clothes are good insulators because of trapped air.

 

Def: A tog value is a measure of insulation. (Measures from 1 – 13.5)