Step-by-step explanation:
When we heat a substance then molecules of the substance start to move from their initial position. As a result, they gain kinetic energy and collide with each other.
This leads to change in phase of the substance.
Molecules of a substance only come in motion when the heat gained by them overcomes the electrostatic force of attraction between the molecules.
For example, heating some ice cubes will convert solid state of water in liquid state.
Therefore, we can conclude that when heating a substance, a phase change will occur when the kinetic energy of the particles is great enough to over come the attractive forces between the particles.