To identify chemical changes, we look for reactions that result in the formation of new substances with different chemical properties. Examples of chemical changes include burning, where a substance reacts with oxygen to form new compounds like carbon dioxide; rusting, where iron reacts with oxygen to form iron oxide; and cooking, where ingredients undergo chemical transformations to create new substances. Baking also involves chemical reactions that alter the original ingredients. In contrast, physical changes, such as melting, freezing, or tearing, do not result in new substances but only in changes in state or appearance. Chemical changes always involve a change in composition, unlike physical changes.