Describe how the particles and energy change as you go from a solid to a liquid to a gas.
In a solid, the particles are touching, and the only motion allowed to them is vibration. (Particles in a solid are held together by forces which depend on the actual substance... ionic bonds, convalent bonds, metallic bonds, hydrogen bonds).
In a liquid are mainly touching, but some gaps have appeared in the structure. These gaps allow the particles to move. The particles are arranged randomly. They are still touching and are still close together.
In a gas, the particles are entirely free to move around.