lt is a synonymous of Specific Heat. Specific Heat is the heat capacity per unit mass. 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: ΔQ=m.c.ΔT where, ΔQ= Heat supplied to substance, m= Mass of the substance, c= Specific heat capacity, ΔT= Temperature rise. There are two definitions for vapours and gases: c_p = Specific heat capacity at constant pressure, i.e. C_P = (1/m)(∂H/∂T) _P. c_v = Specific heat capacity at constant volume, i.e. C_V = (1/m)(∂U/∂T)_V. It can be shown that for a perfect gas: C_P - C_V =R where R is the gas constant. The ratio, cp/cv, as been given symbol γ, =C_p/C_vand 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 SO₂and CO₂) 1.3. The specific heat capacity (symbol c or s, also called specific heat) of a substance is defined as heat capacity per unit mass. The SI unit for specific heat capacity is the joule per kilogram Kelvin, J?kg^-1?K^-1 or J/(kg?K), which is the amount of energy required to raise the temperature of one kilogram of the substance by one Kelvin. Heat capacity can be measured by using calorimetry. The equivalent definition using cgs units is the amount of energy (measured in ergs) required to raise the temperature of one gram of the substance by one degree Celsius (erg/(g??C)). Other units of specific heat capacity include calories per gram degree Celsius (cal/(g??C) or cal/(g?K)) and Btu per pound degree Fahrenheit (Btu/(lb??F)) The symbol c_p is often used to denote specific heat capacity at constant pressure. Substances with low specific heat such as metals require less input energy to increase their temperature. Substances with high specific heat such as water require much more energy to increase their temperature. The specific heat can also be interpreted as a measure of how well a substance preserves its temperature, i.e. "stores" heat, hence the term "heat capacity"