The molecules lose kinetic energy as the solid heats up and goes from a crystalline structure to a disordered liquid state. Ice is a solid phase of water where the molecules are ordered in a crystalline structure. When ice melts, heat energy is absorbed from its surroundings and the molecules lose kinetic energy as they go from an ordered state to a disordered liquid state and gravity kicks in. Heat is transferred to ice when it melts. The heat energy causes the molecules to gain kinetic energy and speed up.