What is chemical change?

Chemical changes are changes that result in the formation of a new substance. In other words, the composition of a substance changes when the substance undergoes a chemical change. Chemical reactions are chemical changes. Examples of chemical changes (and reactions) are combustion, decomposition, fermentation, and oxidation. Color changes, the formation of bubbles, and the formation of a precipitate are often indicators that a chemical change has occurred.

Another type of change is a physical change. The composition of a substance does not change during physical change. Physical changes may result in a change of the form, appearance, shape, or size of a substance changes. All phase changes are physical changes. Other examples of physical changes include snapping, smashing, cracking, stretching, cutting, and dissolving.