physics notes

Specific Heat Capacity

The specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature. This can be stated by the following equation:

where,
Q= Heat supplied to substance,
m= Mass of the substance,
c= Specific heat capacity,
T= Temperature rise.

There are two definitions for vapors and gases:
Cp = Specific heat capacity at constant pressure, i.e.

Cv = Specific heat capacity at constant volume, i.e.

It can be shown that for a perfect gas:

where R is the gas constant. The ratio, Cp/Cv, has been given symbol ,

and is always greater than unity. The approximate value of this ratio is 1.6 for monatomic gases such as Ar and He. Diatomic gases (such as H2, N2, CO and O2) have a g ratio about 1.4 and triatomics (such as SO2 and CO2) 1.3.