decomposition

Chemical change in which one substance is broken down into two or more simpler substances. In biology, decomposition is the result of the action of decomposer organisms, such as bacteria and fungi. The decomposer organisms obtain food from dead organisms, such as carbon compounds, which are energy-rich. These organisms have an important role in the cycling of carbon compounds as part of the carbon cycle. The respiration of the organisms releases carbon dioxide back into the atmosphere. Other organisms feed on the decomposers and they are part of the decomposer food chain. The decomposition of dead plants and animals allows chemicals to be washed out of the decaying remains into the soil. Many of these are important nutrients that plants can use.

In chemistry, there are three main types of decompositions - thermal, electrolytic, and catalysed.

Thermal decomposition occurs as a result of heating. For example, copper(II) carbonate decomposes on heating to give copper oxide and carbon dioxide:

CuCO₃ → CuO + CO₂

Electrolytic decomposition may result when an electrical current is passed through a compound in the molten state or in aqueous solution. For example, molten sodium chloride breaks down into sodium and chlorine:

2NaCl → 2Na + Cl₂

Catalysed decomposition describes the process by which decomposition is aided by the presence of a catalyst. For example, hydrogen peroxide decomposes more quickly with the use of manganese(IV) oxide:

2H₂O₂ → 2H₂O + O₂