Matter can change in two ways: physically or chemically. Physical changes alter the state of matter through melting, freezing, evaporation, or condensation, but do not change its chemical composition. Chemical changes result in new substances forming through combustion, oxidation, or other chemical reactions. Some examples of physical changes include ice melting into water and water evaporating to form vapor, while examples of chemical changes include wood burning to form ashes and iron rusting when exposed to oxygen.