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. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature 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. Marcellin (or Marcelin Pierre Eugène Berthelot ( October 25, 1827 - March 18, 1907) was a French Chemist and Politician The opposite of an exothermic process is an endothermic process, one that absorbs energy in the form of heat. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat.
The concept is frequently applied in physical sciences to chemical reactions, where chemical bond energy is converted to thermal energy (heat). Physical science is an encompassing term for the branches of Natural science and Science that study non-living systems in contrast to the biological sciences A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called In Chemistry, bond energy ( E) is a measure of Bond strength in a Chemical bond. Thermal energy is the sum of the sensible energy and latent energy.
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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]
In chemical reactions, the heat that is released is in the form of electromagnetic energy. The loss of kinetic energy via reacting electrons causes light to be released. This light is equivalent in energy to the stabilization energy of the energy for the chemical reaction, i. e. the bond energy. This light that is released can be absorbed by other molecules in solution to give rise to molecular vibrations or rotations, which gives rise to the classical understanding of heat. In contrast, when endothermic reactions occur, energy is absorbed to place an electron in a higher energy state, such that the electron can associate with another atom to form another chemical complex. The loss of energy within solution is absorbed by the endothermic reaction and therefore is a loss of heat. This is the physical understanding of exothermic and endothermic reactions within solution.
Examples
Some examples of exothermic processes are:[2]
- Condensation of rain from water vapour
- Combustion of fuels such as wood, coal and oil
- Mixing water and strong acids
- Mixing alkalis and acids
- The setting of cement and concrete
- Most polymerisation reactions such as the setting of epoxy resin
- Thermite reaction
Implications for chemical reactions
Chemical exothermic reactions are generally more spontaneous than their counterparts, endothermic reactions. Fuel is any material that is burned or altered in order to obtain energy Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is A Strong acid is an Acid that Ionizes completely in an Aqueous solution (not in the case of Sulfuric acid as it is diprotic In Chemistry, an alkali (from Arabic: Al-Qaly القلي القالي) is a basic, ionic salt of an Alkali metal In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In the most general sense of the word a cement is a binder a substance which sets and hardens independently and can bind other materials together Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag In Polymer chemistry, polymerization is a process of reacting Monomer Molecules together in a Chemical reaction to form three-dimensional networks In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a Thermite is a Pyrotechnic composition of Aluminium powder and a metal oxide which produces an Aluminothermic reaction known as a An exothermic reaction is a Chemical reaction that releases Heat. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. In a thermochemical reaction that is exothermic, the heat may be listed among the products of the reaction.
See also
- Calorimetry
- Chemical thermodynamics
- Differential scanning calorimetry
- Endergonic
- Endergonic reaction
- Exergonic
- Exergonic reaction
External links
- http://chemistry.about.com/b/a/184556.htm Observe exothermic reactions in a simple experiment
References
- ^ Perrot, Pierre (1998). Calorimetry is the Science of measuring the Heat of Chemical In Thermodynamics, chemical thermodynamics is the mathematical study of the interrelation of Heat and work with Chemical reactions or with a Differential scanning calorimetry or DSC is a thermoanalytical technique in which the difference in the amount of Heat required to increase the Temperature 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, In chemical thermodynamics, an endergonic reaction (also called an unfavorable reaction or a nonspontaneous reaction) is a chemical reaction in which the Exergonic means to release energy in the form of work Its etymology stems from the suffix -ergonic, as derived from the Greek root ergon meaning work, An exergonic reaction is a chemical reaction that involves a net release of free energy is a Chemical reaction where the variation of Gibbs free energy is negative A to Z of Thermodynamics. Oxford University Press. ISBN 0-19-856552-6.
- ^ Exothermic - Endothermic examples
Dictionary
exothermic
-adjective
- (chemistry, of a reaction) That releases energy in the form of heat.
- (chemistry, of a compound) That releases heat during its formation, and absorbs it during its decomposition
- (zoology) Of an animal whose body temperature is regulated by external factors; cold-blooded
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