Clausius

Hermann von Helmholtz puts forward the idea of the heat death of the universe in 1854, the same year that Clausius established the importance of dQ/T ( Clausius's theorem ) (though he did not yet name the quantity).

Classical thermodynamics main The thermodynamic definition of entropy was developed in the early 1850s by Rudolf Clausius and essentially describes how to measure the entropy of an isolated system in thermodynamic equilibrium with its parts.

Clausius called this state function entropy.

Clausius wrote that he "intentionally formed the word Entropy as similar as possible to the word Energy", basing the term on the Greek ἡ τροπή tropē, "transformation".

History In 1870, Rudolf Clausius delivered the lecture "On a Mechanical Theorem Applicable to Heat" to the Association for Natural and Medical Sciences of the Lower Rhine, following a 20 year study of thermodynamics.

In the continuum mechanics of solids, the second law of thermodynamics is satisfied if the Clausius–Duhem form of the entropy inequality is satisfied.

The second Law was the idea that gases consist of molecules in motion had been discussed in some detail by Daniel Bernoulli in 1738, but had fallen out of favor, and was revived by Clausius in 1857.

This includes a required rethink of the probability of vaporization, and has consequences to the Clausius-Clapeyron equation.

While Clausius based his definition on a reversible process, there are also irreversible processes that change entropy.

While there he undertook a program of mostly self-study of Clausius's writings, which led him to choose thermodynamics as his field.