Endothermic
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In thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs energy in the form of heat. Its etymology stems from the Greek prefix endo-, meaning “inside” and the Greek suffix –thermic, meaning “to 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.
The concept is frequently applied in physical sciences to e.g. chemical reactions, where thermal energy (heat) is converted to chemical bond energy.
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[edit] Overview
Endothermic, also incorrectly known as endergonic, refers to a chemical reaction in which a system receives heat from the surroundings:
- Q > 0
When this occurs at constant pressure:
- ∆H > 0
and constant volume:
- ∆U > 0
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 system.[1]
[edit] Endothermic processes
Some examples of endothermic processes are:[2]
- Depressurising a pressure can
- A chemical cold pack consisting primarily of ammonium nitrate and water.
- Melting of ice
- vaporisation of water
[edit] 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).
[edit] See also
[edit] References
- ^ Perrot, Pierre (1998). A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6.
- ^ Exothermic - Endothermic examples
[edit] External links
- Endothermic Definition - MSDS Hyper-Glossary
- School experiment
