When a particle is heated The intermolecular forces are the attractions between the molecules when temperature increases it develops more distance between molecules and because of this attraction decreases, resulting intermolecular force decreases. Intermolecular forces decreases on heating as the particles gain energy and start vibrating. The intermolecular space between particles increases and they overcome the intermolecular forces. Hence, the intermolecular forces decrease on heating because kinetic energy increases and space between particles increases.