Procedure : 

1. Take small ice cube in a beaker. Insert the thermometer in the beaker. 

2. Now start heating the beaker and note down readings of thermometer every one minute till the ice completely melts and gets converted into water. 

3. Before heating the temperature of ice is 0° C or less than 0° C.

Observation :

1. We will observe that the temperature of ice at the beginning is equal to or below 0°C. 

2. If the temperature of ice is below 0°C, it goes on changing till it reaches 0° C. 

3. When ice starts melting, we will observe no change in temperature though you are supplying heat continuously.

Explanation : 

1. Given heat energy is used to break the bonds (H₂O) in ice and melts. 

2. So, temperature is constant while melting.

Conclusion : 

1. This process is called melting. In this process heat converts solid phase to liquid phase. 

2. The temperature of the substance does not change until all the ice melts and converts into water. 

3. The heat given to melting is called latent heat of fusion. 

4. The heat required to convert 1 gm of solid completely to liquid at constant temperature is called “latent heat of fusion”.

m = 5 gm; L_f = 80 cal/g

The amount of heat absorbed Q = ML_f = 5 × 80 = 400 cal /g.