WordNet

transformation of a substance produced by the action of heat
resulting from pyrolysis
(chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance (同)decomposition reaction, chemical decomposition reaction
in a decomposed state (同)disintegration
(biology) the process of decay caused by bacterial or fungal action (同)rot, rotting, putrefaction
the analysis of a vector field (同)vector decomposition
of or relating to a hot spring; "thermal water"
rising current of warm air
relating to or associated with heat; "thermal movements of molecules"; "thermal capacity"; "thermic energy"; "the caloric effect of sunlight" (同)thermic, caloric
caused by or designed to retain heat; "a thermal burn"; "thermal underwear"
a unit of heat equal to 100,000 British thermal units

PrepTutorEJDIC

(有機化合物の)熱分解
分解　腐敗　変質
熱の,熱による / 熱い / (暖まった)上昇気流

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/11/09 20:47:56」(JST)

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Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes.

The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.

Examples

Calcium carbonate (limestone or chalk) decomposes into calcium oxide and carbon dioxide when heated. The chemical reaction is as follows:

CaCO₃ → CaO + CO₂

The reaction is used to make quick lime, which is an industrially important product.

Equipment used by Priestley in his experiments on gases

Some oxides, especially of weakly electropositive metals decompose when heated to high enough temperature. A classical example is the decomposition of mercuric oxide to give oxygen and mercury metal. The reaction was used by Joseph Priestley to prepare samples of gaseous oxygen for the first time.
When water is heated to well over 2000 °C, a small percentage of it will decompose into OH, monoatomic oxygen, monotomic hydrogen, O₂, and H₂.^[1]
The compound with the highest known decomposition temperature is carbon monoxide at ≈3870 °C (≈7000 °F).^{[citation needed]}.

Decomposition of nitrates, nitrites and ammonium compounds

Ammonium dichromate on heating yields nitrogen, water and chromium(III) oxide.
Ammonium nitrate on strong heating yields dinitrogen oxide ("laughing gas") and water.
Ammonium nitrite on heating yields nitrogen gas and water.
Barium azide on heating yields barium metal and nitrogen gas.
Sodium nitrate on heating yields sodium nitrite and oxygen gas.
Organic compounds like tertiary amines on heating undergo Hoffmann elimination and yield secondary amines and alkenes.

Ease of decomposition

When metals are near the bottom of the reactivity series, their compounds generally decompose easily at high temperatures. This is because stronger bonds form between atoms towards the top of the reactivity series, and strong bonds break less easily. For example, copper is near the bottom of the reactivity series, and copper sulfate (CuSO₄), begins to decompose at about 200 °C, increasing rapidly at higher temperatures to about 560 °C. In contrast potassium is near the top of the reactivity series, and potassium sulfate (K₂SO₄) does not decompose at its melting point of about 1069 °C, nor even at its boiling point.

References

^ Baykara, S (2004). "Hydrogen production by direct solar thermal decomposition of water, possibilities for improvement of process efficiency". International Journal of Hydrogen Energy. 29 (14): 1451–1458. doi:10.1016/j.ijhydene.2004.02.014.

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