Difference between revisions of "Thermodynamics"
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| − | Thermodynamics is the study of the effects of work, heat, and energy on a system. Thermodynamics is only concerned with large | + | 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>. |
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| + | ==Thermodynamics and statistical mechanics== | ||
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| + | 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. | ||
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| + | "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><ref>Gregory H. Wannier, ''Statistical Physics'', John Wiley & Sons, New York, 1966</ref> | ||
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| + | ;[[The Zeroth Law of Thermodynamics]] | ||
| + | :allows us to define the concept of [[temperature]], by stating that "''Two systems in thermal [[equilibrium]] with a third one are in thermal equilibrium with each other''". This law is called "zeroth" because it was only formulated after the three others, but is actually more fundamental, and hence deserves a lower number. | ||
| + | ;[[The First Law of Thermodynamics]] | ||
| + | :states that [[energy]] is conserved and that [[heat]] is a form of energy. | ||
| + | ;The [[Second Law of Thermodynamics]] | ||
| + | :states (in one of its various formulations) that the [[entropy]] in an ''isolated'' system cannot decrease, and that ''irreverible processes'' can only make it increase. | ||
| + | ;[[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. | ||
| + | |||
| + | These laws tell us to what constraints ''any'' system is subject. The particular properties of a specific system cannot be calculated from these laws alone. More information is required: material constants, such as [[specific heat]] or [[isothermal compressibility]], tell us how a particular system will behave under thermodynamic processes. | ||
== References == | == References == | ||
<div class="references-small"> | <div class="references-small"> | ||
<references /> | <references /> | ||
Revision as of 20:57, March 12, 2007
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.[1].
Thermodynamics and statistical mechanics
For systems consisting of many particles (such as a gas consisting of many molecules), 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 engines. Well-known "laws" of thermodynamics are[2][3]
- The Zeroth Law of Thermodynamics
- allows us to define the concept of temperature, by stating that "Two systems in thermal equilibrium with a third one are in thermal equilibrium with each other". This law is called "zeroth" because it was only formulated after the three others, but is actually more fundamental, and hence deserves a lower number.
- The First Law of Thermodynamics
- states that energy is conserved and that heat is a form of energy.
- The Second Law of Thermodynamics
- states (in one of its various formulations) that the entropy in an isolated system cannot decrease, and that irreverible processes can only make it increase.
- 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.
These laws tell us to what constraints any system is subject. The particular properties of a specific system cannot be calculated from these laws alone. More information is required: material constants, such as specific heat or isothermal compressibility, tell us how a particular system will behave under thermodynamic processes.
References
- ↑ http://www.grc.nasa.gov/WWW/K-12/airplane/thermo.html
- ↑ Mark W. Zemansky, Heat and Thermodynamics, McGraw-Hill, New York, 1957
- ↑ Gregory H. Wannier, Statistical Physics, John Wiley & Sons, New York, 1966