Physical properties are those that can be seen or used without changing their physical properties or identities, while chemical properties are those that change in structure and composition. Physical properties share the same suite of general properties of matter, which includes color, density and hardness. Chemical properties, however, are characterized by properties that change, such as flammability, corrosion and oxidation resistance.
The transformation of a material does not necessarily mean that its properties change from physical to chemical in composition. When materials change from solids to liquid vapors, for instance, they do not become different substances; only their shape and states change. For example, ice, liquid water and water vapor are all still considered water, just in different forms. When materials undergo phase transformations, their physical properties change. Phase is a physical property of matter, and it may exist in one of four classical phases: solid, gas, liquid and plasma. Phase transitions ordinarily include transitions from liquids to solids and from liquids to vapors. Occasionally, solids may transition to liquids, and solids to other solids. Physical and chemical properties are important in determining the density, specific gravity, thermal conductivity and corrosion resistance of elements, compounds, alloys and mixtures.