Physical changes are those in which the shape, size, or state of the matter changes, but the substance is still essentially the same. For example, chopping up a carrot or ice melting into water are both physical changes.

Examples:

- cutting a log into smaller pieces.    
- wearing away of rock by wind-blown sand.    
- braiding hair.    
- crushing a metal can.    
- melting chocolate

Chemical changes are those where one or more substances are combined to produce a new substance. Example: Burning a piece of paper, or baking a cake.