In thermodynamics, entropy models are any of various verbal, visual, heuristic, or statistical teaching models used to describe the 1865 quantity 'entropy', defined in various ways by German physicist Rudolf Clausius during the years 1850 to 1875. Some of the various oft-cited entropy models are as follows:

Model		Picture	Notes

Four element theory Aristotle	350BC		Denser elements tend to rise; lighter elements fall; earth is the heaviest element; fire the lightest. “For any two portions of fire, small or great, will exhibit the same ratio of solid to void; but the upward movement of the greater is quicker than that of the less.”
Three principles Geber	790		Metals are formed of two elements: sulphur, ‘the stone which burns’, the principle of combustibility, and mercury, the principle of metallic properties. Salt gives solidity.
Sulphur combustion model Paracelsus	1524
Terra pinguis model Johann Becher	1699
Phlogiston model Georg Stahl	1703
Caloric model Antoine Lavoisier (1789)	1789
Re-establishment of equilibrium in the caloric Sadi Carnot	1824		A Lavoisier-base view that heat consisted of indestructible caloric particles and that a body returned to its original position (state) at the end of one heat cycle.
Transformation content Rudolf Clausius	1850
Dissipation (law of dissipation) William Thomson	1852
Disgregation Rudolf Clausius	1862		[3]
Entropy (melting ice) Rudolf Clausius	1862		[1]
	1870		“The second law of thermodynamics has the same degree of truth as the statement that if you throw a tumblerful into the sea, you cannot get the same tumblerful out again.” — James Maxwell (1870), “Letter to John Strutt”, Dec 6; the “moral” of his Maxwell’s demon argument [21]
Velocity distribution model (H-theorem) Ludwig Boltzmann	1872
Entropy of mixing Willard Gibbs	1876		Note: this could have been Gibbs' 1902 work; see: Gilbert Lewis' 1925 The Anatomy of Science (pg. 148).
Disorder Hermann Helmholtz	1882
Ghostly quantity John Perry	1899
S = k ln W Max Planck	1901
Mixed-up-ness Willard Gibbs	1903		Note: ditto to previous note.
Elementary disorder Max Planck	1906
Typing monkeys Emile Borel (1913)	1913
Entropies of bodies Gilbert Lewis	1923
Entropy (shuffling cards) Gilbert Lewis Arthur Eddington	1925		Seems to have been first described in Lewis' The Anatomy of Science (1925); then expanded be Eddington in his The Nature of the Physical World (1928).
Arrow of time Arthur Eddington	1928
Entropy (information) Leo Szilard (1929)	1929
Information theory Claude Shannon	1948		Note: this has nothing to do with thermodynamics; contrary to popular opinion; but rather is a mis-informed urban myth existing in ignorant science.
Unscrambled eggs (Broken eggs) Walter Albersheim?	1955
Entropy (child’s playroom) Peter Landsberg	1961
Energy dispersal Peter Atkins	1984
(spreading out of energy) Frank Lambert	1999	Entropy ≠ Disorder	In a view of entropy as "energy spreading out"; a misinformed view promoted by American organic chemist Frank Lambert; based on a reading of one of William Thomson's articles.

See also
● Entropy formulations
● Entropy (misinterpretations)

References
1. Sladek, John T. (1974). The New Apocrypha: a Guide to Strange Science and Occult Beliefs (pg. 258). Stein and Day.
2. Lindberg, David C., Porter, Roy, Jo Nye, Mary, and Numbers, Ronald. (2003). The Cambridge History of Science: the Modern Physical and Mathematical Sciences (pgs. 494-95). Cambridge University Press.
3. Disgregation – Wikipedia.