* Physical Changes alter the form or appearance of a substance but not its chemical composition. The molecules themselves remain the same.

* Chemical Changes involve the formation of new substances with different chemical properties.

Examples of Phase Changes:

* Melting: Solid to liquid (ice to water)

* Freezing: Liquid to solid (water to ice)

* Boiling: Liquid to gas (water to steam)

* Condensation: Gas to liquid (steam to water)

* Sublimation: Solid to gas (dry ice to carbon dioxide gas)

* Deposition: Gas to solid (frost forming on a window)

In each of these phase changes, the chemical makeup of the substance (water, for example) remains the same. Only the arrangement and movement of the molecules change.