Introduction

Heat is a form of energy which flows from an area of high temperature to an area of low temperature .

Heat as a form of energy can be transformed from one form to another

The unit of heat is joule because is a form of energy.

Specific heat capacity

The quantity of heat Q in Joule transfer to a body is directly proportional to its' mass m and change in temperature , while the material involve remains the same i.e the nature of the material  (metal , water or wood etc.)

 =mc

The C is the  constant of proportionality.

This value depends on the nature of the material.

C is called the specific heat capacity of the material

The  unit of specific heat capacity is

When m=1 and   then Q=C

We can now define C with respect to these values.

The specific heat capacity of a substance is defined as the quantity of heat required to raise the temperature of a unit mass of the substance by one degree rise in temperature.

The specific heat capacity of some substances are listed in the table below.

Specific Heat capacity table.

The heat capacity

The heat capacity of a substance is dependent on the mass of the substance, while the specific heat capacity is independent of the mass of the substance. Therefore heat capacity is a function of mass.

From the expression

If heat capacity =H

Then  Q=H   where H=mC  =    heat capacity

Therefore ,

Heat capacity = mass  x  Specific heat capacity

The heat capacity of a substance can be defined as the quantity of heat required to raise the temperature of the complete mass of the substance through one degree rise in temperature.

The unit of heat capacity H  is joule/kelvin 

Example

What is the mass of water with heat capacity of 8400   ? C=4200 .

Solution

H=mC

m=H/C

=8400/4200= 2Kg

Find the heat require to raise the temperature of 30Kg of water through 20K. Take C=4200

Solution

Q=mC=30 x 20 x 4200 = 2520000 Joules

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