Endergonic

Endergonic means absorbing energy in the form of work. Its etymology stems from the suffix -ergonic as derived from the Greek root ergon meaning work, combined with the prefix end- as derived from the Greek root en meaning put into. By thermodynamic standards, work, a form of energy, is defined normally to move from the surroundings (the external region) to the system (the internal region). Thus, an endergonic process, as contrasted with an exergonic process, is one where the system absorbs energy from the surroundings. Subsequently, during an endergonic process energy is put into the system. If the transformation occurs at constant pressure and temperature: ∆G > 0. An endergonic reaction is a chemical reaction that absorbs energy in the form of work.

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An endergonic reaction is essentially the opposite of an exergonic reaction. Since endergonic reactions require energy, they form molecular bonds, which decreases entropy. These bonds are energy carriers, therefore the formation of these bonds require some energy input.

'Cold packs' which become cold after mixing two liquids, exploit this property. In fact, a common reaction which is clearly endergonic is the mixing of ammonium chloride and water. There is a net drop in temperature of the reaction as a result of the solvation of Ammonium ion

See also