For the biological process, see Decomposition. For chemical decomposition in general, see Chemical decomposition.

Thermal decomposition, also called thermolysis, is defined as a chemical reaction whereby a chemical substance breaks up into at least two chemical substances when heated. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. The decomposition temperature of a substance is the temperature at which the substance decomposes into smaller substances or into its constituent atoms. Image File history File links No higher resolution available. ... For other uses, see Decomposition (disambiguation). ... Chemical decomposition or analysis is the fragmentation of a chemical compound into elements or smaller compounds. ... For other uses, see Chemical reaction (disambiguation). ... Water and steam are two different forms of the same chemical substance A chemical substance is a material with a definite chemical composition. ... This article is about the physical effect. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... For other uses, see Temperature (disambiguation). ... Chemical decomposition or analysis is the fragmentation of a chemical compound into elements or smaller compounds. ... Properties For alternative meanings see atom (disambiguation). ...

For example, calcium carbonate decomposes into calcium oxide and carbon dioxide. Some compounds, on the other hand, simply decompose into their constituent elements. Water, when heated to well over 2000 degrees Celsius, breaks up into its components - hydrogen and oxygen. Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... Calcium oxide (CaO), commonly known as burnt lime, lime or quicklime, is a widely used chemical compound. ... Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Celsius (disambiguation). ... This article is about the chemistry of hydrogen. ... This article is about the chemical element and its most stable form, or dioxygen. ...

A common example is the decomposition of copper carbonate into copper oxide and carbon dioxide, seen here: Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming most of the patina one sees on weathered brass, bronze, and copper. ... Copper forms two oxides, copper(I) oxide (cuprous oxide, Cu2O) a red powder and copper(II) oxide (cupric oxide, CuO) a black powder. ... Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...

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. Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming most of the patina one sees on weathered brass, bronze, and copper. ... Copper(II) oxide or cupric oxide (CuO) is the higher oxide of copper. ... Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming most of the patina one sees on weathered brass, bronze, and copper. ... Copper forms two oxides, copper(I) oxide (cuprous oxide, Cu2O) a red powder and copper(II) oxide (cupric oxide, CuO) a black powder. ... Carbon dioxide (chemical formula: CO2) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...

Decomposition may be aided by the presence of a catalyst. For example, hydrogen peroxide decomposes more quickly with the use of manganese(IV) oxide:

2H₂O₂(aq) → 2H₂O(l) + O₂(g)

High temperatures can also induce polymerization, which produces larger molecules, possibly also causing thermal decomposition and evaporation of smaller molecules in the process. Such reactions are called pyrolysis reactions. A common example is coking, which is the formation of an amorphous carbon structure along with the evaporation of hydrogen and other pyrolysis gases. An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... Simple sketch of pyrolysis chemistry Pyrolysis usually means the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam. ... This page is a candidate to be moved to Wiktionary. ...

If thermal decomposition of a substance is significantly exothermic, then the substance is thermodynamically unstable. If initiated, its decomposition forms a positive feedback loop and undergoes thermal runaway up to the point of causing an explosion. This article is about Thermal runaway. ...