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From Nordan Symposia
Jump to navigationJump to searchCreated page with 'File:lighterstill.jpgright|frame ==Etymology== Latin cohaesus, past participle of cohaerēre *Date: [http://www.wikipedia.org/wiki/17th_Century 166...'
[[File:lighterstill.jpg]][[File:Cohesion.jpg|right|frame]]
==Etymology==
[[Latin]] cohaesus, past participle of cohaerēre
*Date: [http://www.wikipedia.org/wiki/17th_Century 1660]
==Definitions==
*1 : the [[act]] or [[state]] of sticking [[together]] tightly; especially : [[unity]] <the lack of cohesion in the Party — Times Literary Supplement>
*2 : [[union]] between similar plant parts or organs
*3 : [[molecular]] [[attraction]] by which the [[particles]] of a [[body]] are united throughout the [[mass]]
==Description==
'''Cohesion''' (n. lat. cohaerere "stick or stay [[together]]") or cohesive [[attraction]] or cohesive [[force]] is a [[physical]] [[property]] of a substance, caused by the [[Subatomic|intermolecular]] [[attraction]] between ''like''-[[molecules]] within a [[body]] or substance that [[acts]] to unite them.
[[Water]], for example, is strongly cohesive as each [[molecule]] may make four [http://en.wikipedia.org/wiki/Hydrogen hydrogen] bonds to other [[water]] [[molecules]] in a tetrahedral [[configuration]]. This results in a [[relatively]] strong [http://en.wikipedia.org/wiki/Coulomb_force Coulomb force] between [[molecules]]. [http://en.wikipedia.org/wiki/Van_der_Waals_forces Van der Waals] [[gases]] such as [http://en.wikipedia.org/wiki/Methane methane], however, have weak cohesion due only to Van der Waals forces that operate by induced [[polarity]] in non-polar molecules.
Cohesion, along with [http://en.wikipedia.org/wiki/Adhesion adhesion] ([[attraction]] between ''unlike'' [[molecules]]), helps explain [[phenomena]] such as [http://en.wikipedia.org/wiki/Meniscus meniscus], [[surface]] tension and [http://en.wikipedia.org/wiki/Capillary_action capillary action].
[http://en.wikipedia.org/wiki/Mercury_(element) Mercury] in a [[glass]] flask is a good [[example]] of the [[effects]] of the [[ratio]] between cohesive and adhesive [[forces]]. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the bottom of the flask , and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, where the meniscus of water is [http://en.wikipedia.org/wiki/Concave concave] . Mercury will not wet the glass, unlike [[water]] and many other liquids, and if the glass is tipped, it will 'roll' around inside.
[[Category: Chemistry]]
==Etymology==
[[Latin]] cohaesus, past participle of cohaerēre
*Date: [http://www.wikipedia.org/wiki/17th_Century 1660]
==Definitions==
*1 : the [[act]] or [[state]] of sticking [[together]] tightly; especially : [[unity]] <the lack of cohesion in the Party — Times Literary Supplement>
*2 : [[union]] between similar plant parts or organs
*3 : [[molecular]] [[attraction]] by which the [[particles]] of a [[body]] are united throughout the [[mass]]
==Description==
'''Cohesion''' (n. lat. cohaerere "stick or stay [[together]]") or cohesive [[attraction]] or cohesive [[force]] is a [[physical]] [[property]] of a substance, caused by the [[Subatomic|intermolecular]] [[attraction]] between ''like''-[[molecules]] within a [[body]] or substance that [[acts]] to unite them.
[[Water]], for example, is strongly cohesive as each [[molecule]] may make four [http://en.wikipedia.org/wiki/Hydrogen hydrogen] bonds to other [[water]] [[molecules]] in a tetrahedral [[configuration]]. This results in a [[relatively]] strong [http://en.wikipedia.org/wiki/Coulomb_force Coulomb force] between [[molecules]]. [http://en.wikipedia.org/wiki/Van_der_Waals_forces Van der Waals] [[gases]] such as [http://en.wikipedia.org/wiki/Methane methane], however, have weak cohesion due only to Van der Waals forces that operate by induced [[polarity]] in non-polar molecules.
Cohesion, along with [http://en.wikipedia.org/wiki/Adhesion adhesion] ([[attraction]] between ''unlike'' [[molecules]]), helps explain [[phenomena]] such as [http://en.wikipedia.org/wiki/Meniscus meniscus], [[surface]] tension and [http://en.wikipedia.org/wiki/Capillary_action capillary action].
[http://en.wikipedia.org/wiki/Mercury_(element) Mercury] in a [[glass]] flask is a good [[example]] of the [[effects]] of the [[ratio]] between cohesive and adhesive [[forces]]. Because of its high cohesion and low adhesion to the glass, mercury does not spread out to cover the bottom of the flask , and if enough is placed in the flask to cover the bottom, it exhibits a strongly convex meniscus, where the meniscus of water is [http://en.wikipedia.org/wiki/Concave concave] . Mercury will not wet the glass, unlike [[water]] and many other liquids, and if the glass is tipped, it will 'roll' around inside.
[[Category: Chemistry]]
