In thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases energy usually in the form of heat, but it can also release energy in form of light (e.g. explosions), sound, or electricity (e.g. a battery). Its etymology stems from the Greek prefix ex-, meaning “outside” and the Greek word thermein, meaning “to heat”. The term “exothermic” was first coined by Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy in the form of heat. Thermodynamics (from the Greek θερμη, therme, meaning heat and δυναμις, dynamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... Marcellin Berthelot Marcellin (or Marcelin) Pierre Eugène Berthelot (October 25, 1827 - March 18, 1907) was a French chemist and politician noted in thermochemistry for the Thomsen-Berthelot principle. ... This article is about the physical effect. ...

The concept is frequently applied in physical sciences to chemical reactions, where chemical bond energy is converted to thermal energy (heat). Physical science is the branch of science including chemistry and physics, usually contrasted with the social sciences and sometimes including and sometimes contrasted with natural or biological science. ... Chemical reactions are also known as chemical changes. ... In chemistry, bond energy (E) is a measure of bond strength in a chemical bond. ... In thermal physics, thermal energy is the energy portion of a system that increases with its temperature. ...

hey everybody

Overview

Exothermic refers to a transformation in which a system releases energy (heat) to the surroundings:

Q < 0

When the transformation occurs at constant pressure:

∆H < 0

and constant volume:

∆U < 0

In an adiabatic system (e.g. a system that does not give off heat to the surroundings), an exothermic process results in an increase in temperature.^[1] This article covers adiabatic processes in thermodynamics. ...

Exothermic processes

Some examples of exothermic processes are:^[2]

• Condensation of rain from water vapor
• Combustion (for instance of a candle)
• Mixing water and strong acids
• Nuclear fusion

Implications for chemical reactions

Main article: exothermic reaction

Chemical exothermic reactions are generally more spontaneous than their counterparts, endothermic reactions. In a thermochemical reaction that is exothermic, the heat may be listed among the products of the reaction. In chemistry, an exothermic reaction is one that releases heat . ... In Chemistry an endothermic reaction is one in which the reactants have less energy than the products, and thus a net input of energy, usually in the form of heat, is required. ...

See also

Look up exothermic in
Wiktionary, the free dictionary.

• Endergonic
• Endergonic reaction
• Exergonic
• Exergonic reaction

Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... Endergonic means absorbing energy in the form of work. ... An endergonic reaction is a chemical reaction in which the change in free energy is positive. ... Look up exergonic in Wiktionary, the free dictionary. ... An exergonic reaction is a chemical reaction where the variation of free energy is negative. ...

External links

• http://chemistry.about.com/b/a/184556.htm Observe exothermic reactions in a simple experiment

References

1. ^ Perrot, Pierre (1998). A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6. 
2. ^ Exothermic - Endothermic examples