Heat capacity and specific heat capacity



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 = 10C

Therefore,

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 10C. 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 10C. Its SI unit is J/kg0C.

For water,

S = 4200 J/kg0K (SI)

   = 1 calg-1K-1 

For ice,

S = 2100 J/kg0K

   = 0.5 calg-1K-1