Physical changes are alterations in the appearance or form of a substance that do not lead to the formation of a new substance. They are reversible and involve changes in physical properties such as shape, size, or state of matter. For example, when water freezes, it changes from a liquid to a solid but it is still water. Physical changes do not involve any change in the chemical composition of the substance and can occur without any energy change. On the other hand, chemical changes are reactions that result in the formation of new substances with different chemical compositions. They are usually irreversible and involve changes in chemical properties such as color, odor, or reactivity. Chemical changes require energy input or release and involve the breaking and forming of chemical bonds.
