preprints.org > chemistry > physical chemistry > doi: 10.20944/preprints201802.0074.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 8 February 2018 / Approved: 8 February 2018 / Online: 8 February 2018 (18:14:41 CET)
Version 2 : Received: 4 March 2018 / Approved: 5 March 2018 / Online: 5 March 2018 (05:54:00 CET)

The second law of thermodynamics states the increase of entropy, Delta S > 0, for real processes from state A to state B at constant energy from chemistry over biological life and engines to cosmic events. The connection of entropy to information, phase-space and heat is helpful, but does not immediately convince observers of the validity and basis of the second law. This gave grounds for finding a rigorous, but more easily acceptable reformulation. Here we show using statistical mechanics that this principle is equivalent to a force law ⟨⟨f⟩⟩> 0 in systems where mass centres and forces can be identified. The sign of this net force - the average mean force along a path from A to B - determines the direction of the process. The force law applies to a wide range of processes from machines to chemical reactions. The explanation of irreversibility by a driving force appears more plausible than the traditional formulation as it emphasizes the cause instead of the effect of motions.

statistical mechanics; irreversibility; arrow of time; chemical dynamics

CHEMISTRY, Physical Chemistry