Question

Why do the temperature of substance remain constant during it melting and bowling point

Answer 1

It is not bowling point,it is boiling point.

It happens due to latent heat of fusion and latent heat of evaporation.

When a substance reaches its boiling or melting point,the extra heat is utilised for the state change process,which we call as latent heat.

So it seems to be remaining constant for sometime until the total state changes.

Thanks.
Tripathy.

Answer 2

During melting of a substance the solid form of a matter gets converted into liquid state and forms vapour during boiling.
So to change from one phase to other heat is totally utilized.
Hence,no change to have a rise in temperature. So,temperature remains constant.
The temperature is used up on the breaking of the molecules and the temperature remain unchanged.

HOPE IT HELPS:)