Question

In spite of supplying heat, the temperature of the melting solid does not change. Why?

Answer 1

This because of latent heat or hidden heat which is absorbed by the solid to overcome the forces of attraction....so there is no risen of temperature of the melting solid after it reaches its melting point...hope it helps

Answer 2

Because the melting solid must be at a critical point of temp known as the melting point  at this point the heat energy being supplied to the solid is used for breaking the intermolecular bonds holding the particular substance in that state thus the temperature stays constant .This energy being provided is known as Latent heat of evaporation.