Matter changes via two processes: a physical change or a chemical change. Physical changes retain the fundamental identity of a substance without modifying its composition, while chemical changes alter matter into another form having a set of different properties from the original substance.
Matter is traditionally defined as anything that occupies space and exhibits rest mass, or inertia. The three commonly occurring states of matter include solids, liquids and gases. Matter is classified and identified based on its composition and properties. The composition of matter pertains to its separate constituents, while its properties are related to the distinctive characteristics manifested by the different phases of matter. Generally, all matter possess physical and chemical properties.
Physical attributes of matter are either intensive or extensive. Intensive qualities, such as color, density, luster and conductivity, are independent of the quantity of matter. Extensive traits, such as mass, length and volume, vary with respect to the amount of matter. Chemical properties, including heat of combustion, pH levels and electromotive force, enable matter to undergo chemical reactions that alter its internal organization.
When a physical change occurs, only the phase or state of matter is modified. Freezing of water, melting of ice and dissolving sugar in water are examples of physical changes. A chemical change, meanwhile, involves the breakdown or formation of chemical bonds, which restructure the atomic composition of matter. Examples of chemical changes include gasoline burning, bread rising and milk souring.