* Chemical Change: Involves the formation of new substances with different chemical compositions. Think of burning wood (forming ash and gases), rusting metal (iron reacting with oxygen), or baking a cake (ingredients combining to form a new product).

* Physical Change: Alters the form or appearance of a substance but doesn't change its chemical makeup. Examples include melting ice, freezing water, tearing paper, or dissolving sugar in water.

When you spill water, you're simply changing its location and maybe its shape. The water molecules themselves remain the same (H₂O).