In solid state the particles are aiways vibrating from side to side and up and down they are held together by strong bonds when you heat a solid the particles gain highter kinetic energy and moves faster and futher from one another therefore the bonds that hold them together became weaker the dolid now shagegs into a liquid when you heat the liquid futher the oarticles gain more and more kinetic energy and move freely in the space there are no longer held one another by strong bonds the liquid now shanges into a gas