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Thermodynamics
The classical Carnot heat engine
Branches Classical Statistical Chemical Quantum thermodynamics Equilibrium / Non-equilibrium
Laws Zeroth First Second Third
Systems Closed system Open system Isolated system State Equation of state Ideal gas Real gas State of matter Phase (matter) Equilibrium Control volume Instruments Processes Isobaric Isochoric Isothermal Adiabatic Isentropic Isenthalpic Quasistatic Polytropic Free expansion Reversibility Irreversibility Endoreversibility Cycles Heat engines Heat pumps Thermal efficiency
System propertiesNote: Conjugate variables in italics Property diagrams Intensive and extensive properties Process functions Work Heat Functions of state Temperature / Entropy (introduction) Pressure / Volume Chemical potential / Particle number Vapor quality Reduced properties
Material properties Property databases Specific heat capacity  ${\displaystyle c=}$ ${\displaystyle T}$ ${\displaystyle \partial S}$ ${\displaystyle N}$ ${\displaystyle \partial T}$ Compressibility  ${\displaystyle \beta =-}$ ${\displaystyle 1}$ ${\displaystyle \partial V}$ ${\displaystyle V}$ ${\displaystyle \partial p}$ Thermal expansion  ${\displaystyle \alpha =}$ ${\displaystyle 1}$ ${\displaystyle \partial V}$ ${\displaystyle V}$ ${\displaystyle \partial T}$
Equations Carnot's theorem Clausius theorem Fundamental relation Ideal gas law Maxwell relations Onsager reciprocal relations Bridgman's equations Table of thermodynamic equations
Potentials Free energy Free entropy Internal energy ${\displaystyle U(S,V)}$ Enthalpy ${\displaystyle H(S,p)=U+pV}$ Helmholtz free energy ${\displaystyle A(T,V)=U-TS}$ Gibbs free energy ${\displaystyle G(T,p)=H-TS}$
History Culture History General Entropy Gas laws "Perpetual motion" machines Philosophy Entropy and time Entropy and life Brownian ratchet Maxwell's demon Heat death paradox Loschmidt's paradox Synergetics Theories Caloric theory Vis viva ("living force") Mechanical equivalent of heat Motive power Key publications An Inquiry Concerning the Source ... Friction On the Equilibrium of Heterogeneous Substances Reflections on the Motive Power of Fire Timelines Thermodynamics Heat engines Art Education Maxwell's thermodynamic surface Entropy as energy dispersal
Scientists Bernoulli Boltzmann Bridgman Carathéodory Carnot Clapeyron Clausius de Donder Duhem Gibbs von Helmholtz Joule Kelvin Lewis Massieu Maxwell von Mayer Nernst Onsager Planck Rankine Smeaton Stahl Tait Thompson van der Waals Waterston
Other Nucleation Self-assembly Self-organization Order and disorder
Category
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The laws of thermodynamics, in principle, describe the specifics for the transport of heat and work in thermodynamic processes. Since their conception, however, these laws have become some of the most important in all of physics and other branches of science connected to thermodynamics. They are often associated with concepts far beyond what is directly stated in the wording.

History

The first established principle of thermodynamics (which eventually became the Second Law) was formulated by Sadi Carnot in 1824. By 1860, as found in the works of those as Rudolf Clausius and William Thomson, there were two established "principles" of thermodynamics, the first principle and the second principle. As the years passed, these principles turned into "laws." By 1873, for example, thermodynamicist Josiah Willard Gibbs, in his “Graphical Methods in the Thermodynamics of Fluids”, clearly stated that there were two absolute laws of thermodynamics, a first law and a second law.

Presently, there are a total of five laws. Over the last 80 years or so, occasionally, various writers have suggested adding Laws, but none of them have been widely accepted.

Overview

• Zeroth law of thermodynamics

  ${\displaystyle A\sim B\wedge B\sim C\Rightarrow A\sim C}$

• First law of thermodynamics

  ${\displaystyle \mathrm {d} U=\delta Q-\delta W\,}$

• Second law of thermodynamics

  ${\displaystyle \oint {\frac {\delta Q}{T}}\geq 0}$

• Third law of thermodynamics

  ${\displaystyle T\rightarrow 0,S\rightarrow C}$

• Onsager reciprocal relations - sometimes called the Fourth Law of Thermodynamics

  ${\displaystyle \mathbf {J} _{u}=L_{uu}\,\nabla (1/T)-L_{ur}\,\nabla (m/T)\!}$;

  ${\displaystyle \mathbf {J} _{r}=L_{ru}\,\nabla (1/T)-L_{rr}\,\nabla (m/T)\!}$.

Zeroth law

If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

When two systems are put in contact with each other, there will be a net exchange of energy between them unless or until they are in thermal equilibrium, that is they contain the same amount of thermal energy for a given volume (say, 1 cubic centimetre, or 1 cubic inch.) While this is a fundamental concept of thermodynamics, the need to state it explicitly as a law was not perceived until the first third of the 20th century, long after the first three laws were already widely in use, hence the zero numbering. The Zeroth Law asserts that thermal equilibrium, viewed as a binary relation, is an equivalence relation.

First law

In any process, the total energy of the universe remains at large.

It can also be defined as:

for a thermodynamic cycle the sum of net heat

supplied to the system and the net work done by the system is equal to

zero.

More simply, the First Law states that energy cannot be created or destroyed; rather, the amount of energy lost in a steady state process cannot be greater than the amount of energy gained.

This is the statement of conservation of energy for a thermodynamic system. It refers to the two ways that a closed system transfers energy to and from its surroundings - by the process of heating (or cooling) and the process of mechanical work. The rate of gain or loss in the stored energy of a system is determined by the rates of these two processes. In open systems, the flow of matter is another energy transfer mechanism, and extra terms must be included in the expression of the first law.

The First Law clarifies the nature of energy. It is a stored quantity which is independent of any particular process path, i.e., it is independent of the system history. If a system undergoes a thermodynamic cycle, whether it becomes warmer, cooler, larger, or smaller, then it will have the same amount of energy each time it returns to a particular state. Mathematically speaking, energy is a state function and infinitesimal changes in the energy are exact differentials.

All laws of thermodynamics but the First are statistical and simply describe the tendencies of macroscopic systems. For microscopic systems with few particles, the variations in the parameters become larger than the parameters themselves, and the assumptions of thermodynamics become meaningless. The First Law, i.e. the law of conservation, has become the most secure of all basic laws of science. At present, it is unquestioned.

Second law

The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

In a simple manner, the second law states that "energy systems have a tendency to increase their entropy" rather than decrease it.

A way of looking at the second law for non-scientists is to look at entropy as a measure of chaos. So, for example, a broken cup has less order and more chaos than an intact one. Likewise, solid crystals, the most organized form of matter, have very low entropy values; and gases, which are highly disorganized, have high entropy values.

The entropy of a thermally isolated macroscopic system never decreases (see Maxwell's demon). However, a microscopic system may exhibit fluctuations of entropy opposite to that dictated by the Second Law (see Fluctuation Theorem). In fact, the mathematical proof of the Fluctuation Theorem from time-reversible dynamics and the Axiom of Causality constitutes a proof of the Second Law. In a logical sense the Second Law thus ceases to be a "Law" of physics and instead becomes a theorem which is valid for large systems or long times.

Third law

As temperature approaches absolute zero, the entropy of a system approaches a constant.

In brief, this postulates that entropy is temperature dependent and leads to the formulation of the idea of absolute zero.

Combined law

Aside from the established four basic laws of thermodynamics described above, there is also the combined law of thermodynamics. The combined law of thermodynamics is essentially the first and second laws subsumed into the following single concise mathematical statement:

${\displaystyle dE-TdS+pdV\leq 0.}$

Here, E is energy, T is temperature, S is entropy, p is pressure, and V is volume.

Tentative fourth laws or principles

In the late 19th century, thermodynamicist Ludwig Boltzmann argued that the fundamental object of contention in the life-struggle in the evolution of the organic world is 'available energy'. Since then, over the years, various thermodynamic researchers have come forward to ascribe to or to postulate potential fourth laws of thermodynamics; in some cases, even fifth or sixth laws of thermodynamics are proposed. The majority of these tentative fourth law statements are attempts to apply thermodynamics to evolution. Most fourth law statements, however, are speculative and far from agreed upon.

The most commonly proposed Fourth Law is the Onsager reciprocal relations. Another example is the maximum power principle as put forward initially by biologist Alfred Lotka in his 1922 article Contributions to the Energetics of Evolution. Most variations of hypothetical fourth laws (or principles) have to do with the environmental sciences, biological evolution, or galactic phenomena.

Extended interpretations

The laws of thermodynamics are sometimes interpreted to have a wider significance and implication than simply encoding the experimental results upon which the science of thermodynamics is based. See, for example:

• Principles of energetics
• Heat death

See also

• Conservation law
• Laws of science
• Philosophy of thermal and statistical physics
• Table of thermodynamic equations
• Thermodynamics

References

1. Combined Law of Thermodynamics - Wolfram's World of Science
2. Lehninger, Albert, L. (1973). Bioenergetics, 2nd Ed. ISBN 0-8053-6103-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
3. A.J.Lotka (1922a) 'Contribution to the energetics of evolution' . Proc Natl Acad Sci, 8: pp. 147–51.
4. Morel, R.E. ,Fleck, George. (2006). "Fourth Law of Thermodynamics" Chemistry, Vol. 15, Iss. 4

Further reading

• Goldstein, Martin, and Inge F., 1993. The Refrigerator and the Universe. Harvard Univ. Press. A gentle introduction.

External links

• A Proposed 5 Law of Thermodynamics

• Laws of thermodynamics
• Thermodynamics