Question

Why is heat energy needed to melt a solid? What is this heat energy called?

Answer 1

Heat energy is needed to convert solid into a liquid because heat energy increases the kinetic energy of particles. As the kinetic energy increases, the movement of the particles increases and eventually the bond or attraction between the particles gets broken and the particles start moving faster. Moving faster cause the state of the matter to change because the particles in solid are rigid but when the heat is applied the particles are loosened and start moving freely. So, it changes into a liquid state.
The heat energy that it used to change 1 kg of solid into liquid at atmospheric pressure and its melting point is called the latent heat of fusion.