How would you describe the movement of atoms in a solid? liquid? gas?
Solid: Low kinetic energy
Liquid: Medium kinetic energy
Gas: High kinetic energy
Solid: Particles are closely connected in a crystal lattice, vibrate slightly on the spot
->Has a definite shape and volume
Liquid: Particles roll over one another, can move around, some space between particles
->Has a definite volume but no definite shape
Gas: Particles can move all over the place, spread far apart
->Has no definite shape or volume
Remember: On of the postulates in the particle theory of matter: particles move faster and spread out farther when heated.
This is why when you heat water, steam starts to form: the particles of the liquid water are moving faster (higher kinetic energy) and are spreading out farther. Eventually (at approx. 100 degrees) they move so fast ad spread out so far that there is a change in state, and a gas forms.