Many experiments suggested that the amount of heat energy required to raise the temperature of a substance is directly proportional to:

1. mass (m)

2. change in temperature (∆θ)

This can be expressed as,

Q = ms∆θ è1

Where, s is proportionality constant which is called specific heat capacity. Its value depends on the nature of the substance.

If ∆θ = 1

^{0}CTherefore,

Q = ms

This quantity of heat is called heat capacity or thermal capacity of a substance. It is defined as the amount of energy required to change the temperature of mass of the substance through 1

^{0}C. its unit is called J/K in SI and calorie per Kelvin in CGS.Again from equation 1

s = Q/m∆θ

if m = 1 unit

∆θ = 1 unit

Then,

s = Q

So, the specific heat capacity of a substance is defined as the amount of heat energy required to change the temperature of unit mass through 1

^{0}C. Its SI unit is J/kg^{0}C.For water,

S = 4200 J/kg

^{0}K (SI) = 1 calg

^{-1}K^{-1}For ice,

S = 2100 J/kg

^{0}K

= 0.5 calg

^{-1}K^{-1}