Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Decomposition, in chemistry, the breaking down of a substance or compound, through a chemical reaction, into its simpler components. Such reduction may yield either elements or compounds as products. A common agent of decomposition in chemistry is heat, which can reduce both inorganic and organic compounds to their constituents. Water, for example, decomposes into hydrogen and oxygen when exposed to an electric current. Also, chemical action, as by the use of acids (see Acids and Bases) or alkalies and as accelerated by catalysis, is used in laboratories to reduce compounds. Decomposition is also caused by bacteria, enzymes, and light. Fermentation, for example, occurs because of enzyme actions.

The term decomposition is also applied to the phenomenon of biological decay, or putrefaction, caused by microorganisms. Natural decomposition can also, however, yield useful products, such as petroleum.