* Physical Change: A physical change alters the form or appearance of a substance, but not its chemical composition.

* Chemical Change: A chemical change results in the formation of new substances with different chemical properties.

Twisting a wire only changes its shape and form. The wire is still made of the same material (copper, aluminum, etc.) with the same chemical makeup. No new substances are formed.

Examples of Physical Changes:

* Melting ice

* Boiling water

* Cutting paper

* Crushing a can

Examples of Chemical Changes:

* Burning wood

* Rusting iron

* Baking a cake

* Digesting food