| Term | Definition |
| Solid | A state of matter with definite shape and volume. |
| Crystalline Solid | Solids that are made up of crystals. |
| Melting Point | The temperature at which a solid becomes a liquid. |
| Amorphous Solid | Solids in which the particles are not arranged in a regular repeating pattern. |
| Liquid | A state of matter without definite shape but do have definite volume. |
| Viscosity | The resistance of a liquid to flowing. |
| Gas | A state of matter with neither definite shape nor volume. |
| Thermal Energy | The total kinetic energy of the particles that make up a substance. |
| Melting | Change of state from solid to liquid. |
| Freezing | Change of state from liquid to solid. |
| Vaporization | Change in state from liquid to gas. |
| Evaporation | Vaporization that occurs only on the surface of a liquid. |
| Boiling | Vaporization that occurs throughout a liquid. |
| Boiling Point | The temperature at which a liquid boils. |
| Condensation | Change in state from gas to liquid. |
| Sublimation | A change in state from solid to gas. |