Decomposition, in chemistry, is the breaking down of a substance into simpler products, or into the elements of which it is composed. Decomposition may be brought about in several ways. Heat decomposes red mercuric oxide into its elements of oxygen and bright metallic mercury. Heat breaks down limestone to form lime and carbon dioxide. Heat also decomposes many organic compounds. For example, table sugar breaks down mostly into carbon and water when heated. An electric current decomposes water into its elements hydrogen and oxygen. Many substances are decomposed by chemical action. Starch is broken down into a simple sugar, called glucose, by the action of a boiling, dilute acid. Decomposition may also be caused by the action of light, bacteria, or enzymes. The enzymes in yeast ferment sugar into simple products.
A distinction is usually made between decomposition caused by people, as in chemistry, and decomposition that occurs in nature. For more information on natural or biological decomposition, see Decay.
