Third Law of Thermodynamics

A Third Law of Thermodynamics is physical phenomena law states the entropy of a system in thermal equilibrium approaches a constant value as the temperature approaches absolute zero.

Context
- It is often stated as:

"the entropy of a perfect crystal of any pure substance approaches zero as the temperature approaches absolute zero."

It can be expressed as [math]\displaystyle{ \lim_{T\rightarrow0} (S -S_0) = 0 }[/math] where is the S entropy, T is the absolute temperature and [math]\displaystyle{ S_0 }[/math] is a constant, [math]\displaystyle{ S_0=0 }[/math] for a perfect crystall or any pure substance.

- …
Counter-Example(s)
See: Carnot Efficiency, Laws Of Thermodynamics, Perpetual Motion Machines, Thermodynamics, Physical System, Maxwell's Demon Thought Experiment.

References

2016

(Wikipedia, 2016) ⇒ https://www.wikiwand.com/en/Third_law_of_thermodynamics
- The third law of thermodynamics is sometimes stated as follows, regarding the properties of systems in equilibrium at absolute zero temperature:

"The entropy of a perfect crystal at absolute zero is exactly equal to zero."

At absolute zero (zero kelvin), the system must be in a state with the minimum possible energy, and the above statement of the third law holds true provided that the perfect crystal has only one minimum energy state. Entropy is related to the number of accessible microstates, and for a system consisting of many particles, quantum mechanics indicates that there is only one unique state (called the ground state) with minimum energy. If the system does not have a well-defined order (if its order is glassy, for example), then in practice there will remain some finite entropy as the system is brought to very low temperatures as the system becomes locked into a configuration with non-minimal energy. The constant value is called the residual entropy of the system.

The Nernst–Simon statement of the third law of thermodynamics concerns thermodynamic processes at a fixed, low temperature:

"The entropy change associated with any condensed system undergoing a reversible isothermal process approaches zero as the temperature at which it is performed approaches 0 K."

Here a condensed system refers to liquids and solids. A classical formulation by Nernst (actually a consequence of the Third Law) is:

"It is impossible for any process, no matter how idealized, to reduce the entropy of a system to its absolute-zero value in a finite number of operations."

Physically, the Nernst–Simon statement implies that it is impossible for any procedure to bring a system to the absolute zero of temperature in a finite number of steps.

2012

(Hill, [[2012]) ⇒ Hill, Terrell L.(2012) "An introduction to statistical thermodynamics". Courier Corporation.
- See Pages 49 - 53

2002

(Kaufman, 2002) ⇒ Kaufman, Myron (2002) "Principles of Thermodynamics" CRC Press, 2002.
- See Pages 95 - 97

1963

(Feynman et al., 1963) ⇒ Richard P. Feynman, Robert B. Leighton and Matthew Sands (1963, 1977, 2006, 2010, 2013) "The Feynman Lectures on Physics": New Millennium Edition is now available online by the California Institute of Technology, Michael A. Gottlieb, and Rudolf Pfeiffer ⇒ http://www.feynmanlectures.caltech.edu/
- Second law:A process whose only net result is to take heat from a reservoir and convert it to work is impossible. No heat engine taking heat Q1 from T1 and delivering heat Q2 at T2 can do more work than a reversible engine, for which

[math]\displaystyle{ W=Q1−Q2=Q1(\frac{T1−T2}{T1}) }[/math]

The entropy of a system is defined this way:

(a)If heat [math]\displaystyle{ \Delta Q }[/math] is added reversibly to a system at temperature T, the increase in entropy of the system is [math]\displaystyle{ \Delta S=\Delta Q/T }[/math]

(b)At T=0, S=0 </math>(third law).

In a reversible change, the total entropy of all parts of the system (including reservoirs) does not change. In irreversible change, the total entropy of the system always increases