Thermal decomposition

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Thermal decomposition is a chemical reaction where a chemical substance breaks up into at least two chemical substances when heated. It is an endothermic reaction as heat is required to break chemical bonds in the compound undergoing decomposition. Thermolysis (from thermo- meaning heat and -lysis meaning break down) is a chemical process by which a substance is decomposed into other substances by use of heat. The decomposition temperature of a substance is the temperature at which the substance decomposes into smaller substances or into its constituent atoms. Some compounds decompose into smaller compounds.

For example, calcium carbonate decomposes into calcium oxide and carbon dioxide. Some compounds, on the other hand simply decompose into their constituent atoms. Water, when heated to well over 2000 degrees Celsius, breaks up into hydrogen and oxygen atoms.

A common example is the decomposition of copper carbonate into copper oxide and carbon dioxide, seen here:

CuCO₃ → CuO + CO₂

The copper carbonate turns from a green powder into a black copper oxide, and carbon dioxide is released in a gaseous state.

[edit] As a biological process

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.

[edit] As a chemical process

Main article: chemical decomposition

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:

CuCO_3s → CuO_s + CO_2g

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 gas:

2NaCl_l → 2Na_l + Cl_2g

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:

2H₂O_2aq → 2H₂O_l + O_2g