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'''Thermodynamics''' is the study of the effects of work, heat, and energy on a system. Thermodynamics is only concerned with so-called ''macroscopic'' observations, which are observations on large numbers of particles.<ref>http://www.grc.nasa.gov/WWW/K-12/airplane/thermo.html</ref>.

'''Thermodynamics''' is the study of the effects of work, heat, and energy on a system. Thermodynamics is only concerned with so-called ''macroscopic'' observations, which are observations on large numbers of particles.<ref>http://www.grc.nasa.gov/WWW/K-12/airplane/thermo.html</ref>

==Thermodynamics and statistical mechanics==

==Thermodynamics and statistical mechanics==

For systems consisting of many particles (such as a [[gas]] consisting of many [[molecule]]s), it is possible to describe and predict the properties of the system accurately, even though it is virtually impossible to know what individual particles do. In essence, because of the large number of particles, one can apply [[statistics]] to learn about the "average" behavior of the system. The branch of [[physics]] known as [[statistical mechanics]] does just this.

For systems consisting of many particles (such as a [[gas]] consisting of many [[molecule]]s), it is possible to describe and predict the properties of the system accurately, even though it is virtually impossible to know what individual particles do. In essence, because of the large number of particles, one can apply [[statistics]] to learn about the "average" behavior of the system. The branch of [[physics]] known as [[statistical mechanics]] does just this.

"Classical" thermodynamics, on the other hand, predates this field, and makes ''no'' explicit reference to the constituent particles of a system. It consists of a number of "empirical" laws, which are derived purely from observations on thermodynamical systems, such as vessels of gas, or [[steam engine]]s. Well-known "laws" of thermodynamics are<ref>Mark W. Zemansky, ''Heat and Thermodynamics'', McGraw-Hill, New York, 1957</ref>

"Classical" thermodynamics, on the other hand, predates this field, and makes ''no'' explicit reference to the constituent particles of a system. It consists of a number of "empirical" laws, which are derived purely from observations on thermodynamical systems, such as vessels of gas, or [[steam engine]]s. Well-known "laws" of thermodynamics are:<ref>Mark W. Zemansky, ''Heat and Thermodynamics'', McGraw-Hill, New York, 1957</ref>

;[[The Zeroth Law of Thermodynamics]]

;[[The Zeroth Law of Thermodynamics]]

:states that [[energy]] is conserved and that [[heat]] is a form of energy.

:states that [[energy]] is conserved and that [[heat]] is a form of energy.

;The [[Second Law of Thermodynamics]]

;The [[Second Law of Thermodynamics]]

:states (in one of its various formulations) that [[entropy]] in an isolated system cannot decrease, and that ''irreversible processes'' can only make it increase.<ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref>. An equivalent formulation states that heat cannot spontaneously flow from a cooler body to a hotter body.

:states (in one of its various formulations) that [[entropy]] in an isolated system cannot decrease, and that ''irreversible processes'' can only make it increase.<ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref> An equivalent formulation states that heat cannot spontaneously flow from a cooler body to a hotter body.

;[[The Third Law of Thermodynamics]]

;[[The Third Law of Thermodynamics]]

:also known as ''Nernst's Law'', states that it is not possible to bring any system to the [[absolute zero]] of temperature in a finite number of operations.

:also known as ''Nernst's Law'', states that it is not possible to bring any system to the [[absolute zero]] of temperature in a finite number of operations.

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[[category:physics]]

[[category:physics]]