Physics XI Content





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

 

Have a Question

Ask us in our Discussion forum