ideal gases


Heat capacity

See previous posts about thermal physics

Heat capacity c is a measure of the amount of thermal energy Q can be put into a system before we see a change in its temperature ΔT. It is defined by the equation

where ΔT may be defined as ΔT = T - T0 for an initial temperature T0 and a final temperature T, so

Therefore, if you put 5 J of energy into some volume of liquid, we’ll call it X, which is at an initial temperature T0 = 20°C and observed its temperature change to T = 25°C then it would have a heat capacity cX

Specific heat capacity

This is particularly useful for engineering purposes because a heat capacity can be used to characterise gases and materials etc. For example, the specific heat capacity c of a material is found using its heat capacity per unit mass:

(note that this equation assumes that the heat capacity is independent of mass – i.e. for no phase transitions).