Specific heat capacity

When a substance absorbs heat, its temperature rises (provided that there is no change in state). This isn't too surprising. However, the temperature rise depends on how much heat is added and on the substance involved. Some substances can store quite a lot of heat with only a small temperature rise. Water is an example of such a substance. Specific heat capacity is a measure of this ability to store heat. The units are J g^-1 K^-1.

Temperature rises more slowly for a substance with high specific heat capacity

A substance with a specific heat capacity of 1 J g^-1 K^-1 would rise in temperature by 1 K if 1 joule of heat were gained by 1 gram of substance. Try to think about what this means and the results shouldn't be too surprising. It says that the heat stored is proportional to the mass of substance - in other words if you had twice as much substance it would store twice as much heat. This seems sensible. It also says that the heat stored is proportional to the temperature rise - that is, it would take twice as much heat to raise the temperature by double the amount. This doesn't seem unreasonable either. If you research the physics further you will find that the specific heat capacity does change slightly with temperature. However, for the accuracy required at "A" Level it is reasonable to assume that the specific heat capacity is a constant which is independent of temperature.

We are always dealing with temperature changes when we use specific heat capacity. Remember that temperature changes are exactly the same in ºC as they are in Kelvin. So there is no need to convert from a temperature change in ºC.

Some specific heat capacity values

Substance	Specific Heat capacity (J g^-1K^-1)
Aluminium	0.89
Copper	0.39
Ethanol	2.41
Hexane	2.26
Mercury	0.14
Water	4.18