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Thermal decomposition, orthermolysis, is achemical decomposition of a substance caused by heat. The decomposition temperature of a substance is thetemperature at which the substance chemically decomposes. The reaction is usuallyendothermic as heat is required to breakchemical bonds in the compound undergoing decomposition. If decomposition is sufficientlyexothermic, apositive feedback loop is created producingthermal runaway and possibly anexplosion or other chemical reaction.
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A simple substance (likewater) may exist in equilibrium with its thermal decomposition products, effectively halting the decomposition. The equilibrium fraction of decomposed molecules increases with the temperature.Since thermal decomposition is a kinetic process, the observed temperature of its beginning in most instances will be a function of the experimental conditions and sensitivity of the experimental setup. For a rigorous depiction of the process, the use of thermokinetic modeling is recommended.[1]
main definition:Thermal decomposition is the breakdown of a compound into two or more different substances using heat, and it is an endothermic reaction
When metals are near the bottom of thereactivity series, theircompounds generally decompose easily at high temperatures. This is because strongerbonds form betweenatoms towards the top of the reactivity series, and strong bonds are difficult to break. For example,copper is near the bottom of the reactivity series, andcopper sulfate (CuSO4), begins to decompose at about 200 °C (473 K; 392 °F), increasing rapidly at higher temperatures to about 560 °C (833 K; 1,040 °F). In contrastpotassium is near the top of the reactivity series, andpotassium sulfate (K2SO4) does not decompose at its melting point of about 1,069 °C (1,342 K; 1,956 °F), nor even at its boiling point.
Many scenarios in the real world are affected by thermal degradation. One of the things affected is fingerprints. When anyone touches something, there is residue left from the fingers. If fingers are sweaty, or contain more oils, the residue contains many chemicals. De Paoli and her colleagues conducted a study testing thermal degradation on certain components found in fingerprints. For heat exposure, the amino acid and urea samples started degradation at 100 °C (373 K; 212 °F) and for lactic acid, the decomposition process started around 50 °C (323 K; 122 °F).[3] These components are necessary for further testing, so in the forensics discipline, decomposition of fingerprints is significant.