View source for Internal energy

[[Category:Done 2018-07-20]] 

[[File:waterglass.jpg|300px|thumb|Figure 1. A glass of water is deceivingly calm; internally it is a mass of high speed particles and strong chemical and nuclear bonds.<ref>flyupmike, Pixabay [Online], Available: http://pixabay.com/p-475451/?no_redirect[Accsessed: July 13, 2018]</ref>]]
<onlyinclude>'''Internal energy''' '''<math>(U)</math>''' is the microscopic [[energy]] contained in a substance, given by the random, disordered [[kinetic energy]] of the [[molecule]]s. In addition it includes the [[potential energy]] between these molecules, and the [[nuclear energy]] contained in the [[atom]]s of these molecules.</onlyinclude><ref name=Knight>Randall Knight, ''Physics for Scientists and Engineers,'' 3rd Ed. New York: Pearson, 2013, Ch. 17, p. 470.</ref> Internal energy and [[thermal energy]] are very similar in a basic [[thermodynamics|thermodynamic]] context. However, they differ becuase internal energy encompasses far more than just the average kinetic energy of molecules. This distinction is important because the potential energies between molecules and atoms is important for understanding [[phase change]]s, [[chemical reaction]]s, nuclear reactions, and many more microscopic phenomena.

All objects in space exhibit macroscopic and microscopic energy. Although they are very similar in concept, the main distinction is that microscopic energy cannot be seen. For example, a glass of water on a table has no apparent [[mechanical energy|macroscopic energy]], but on the microscopic scale it is a mass of high speed molecules traveling at hundreds of [[meters per second]].<ref>Hyperphysics, ''Internal energy'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/inteng.html</ref> 

The [[First law of thermodynamics]] states that the internal energy can be changed in a system by doing [[work]] on it, adding/removing [[heat]] from it, or a combination of the two. If the [[system and surrounding|system]] is ''isolated'' it is forbidden from interactions with its surroundings, meaning that the internal energy cannot change. 

==For Further Reading==
*[[Kinetic energy]]
*[[Potential energy]]
*[[Thermal energy]]
*[[System and surrounding]]
*[[First law of thermodynamics]]
*Or explore a [[Special:Random|random page]]


==References==
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