In thermodynamics, the word endothermic ("within-heating") describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the Greek prefix endo-, meaning “inside” and the Greek suffix –ther, meaning “heat”. The opposite of an endothermic process is an exothermic process, one that releases energy in the form of heat. The term endothermic was coined by Marcellin Berthelot (25 October 1827 – 18 March 1907).
The concept is frequently applied in physical sciences to, for example, chemical reactions, where thermal energy (heat) is converted to chemical bond energy.
Endothermic, also known as endergonic, refers to a chemical reaction in which a system receives heat from the surroundings.
When this occurs at constant pressure:
and constant volume:
If the surroundings do not supply heat (e.g., when the system is adiabatic), an endothermic transformation leads to a decrease in the temperature of the cycle.
Some examples of endothermic processes are:
Implications for chemical reactions
Chemical endothermic reactions need heat to be performed. In a thermochemical reaction that is endothermic, the heat is placed on the reactants side (heat is necessary for and absorbed during the reaction).
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