From owner-biophysics@net.bio.net Sat Jan 03 22:00:00 1998 Path: biosci!agate!howland.erols.net!news-peer.gip.net!news-lond.gip.net!news.gsl.net!gip.net!rill.news.pipex.net!pipex!server1.netnews.ja.net!server5.netnews.ja.net!daresbury!not-for-mail From: Pentcho Valev Newsgroups: bionet.biophysics Subject: Validity of thermodynamics Date: 4 Jan 1998 13:04:36 -0000 Lines: 100 Sender: lpddist@mserv1.dl.ac.uk Distribution: bionet Message-ID: <68o1d4$tj@mserv1.dl.ac.uk> Original-To: biophys@dl.ac.uk Bryant Fujimoto wrote:>>>>>>>>>>>>>>>>>>>>> So, before I spend much time trying to fugure out whether any new test has anything to say about the validity of thermodynamics, I want an explanation about why the tests that have already been done are inadequate.<<<<<<<<<<< Bryant, the tests may be adequate and yet there may be problems with the theory. Adequate tests had for a long time proved the existence of a substance called caloric before new tests, within a new paradigm, disproved the concept. This is always the case in science - any developed theory is developed just because it is supported by adequate tests. Still sooner or later internal contradictions appear which initially look insignificant against the great number of supportive tests and lack of any reasonable alternative. However, as soon as a new paradigm emerges, the old one is unavoidably replaced - sometimes we owe this to martyrs (Julius Robert Mayer for instance). So my recent efforts have been directed towards creating the new paradigm - only then can any criticism of the old one be convincing. Otherwise I would continue to repeat endlessly that it is absurd to claim that the system X does work on the system Y whereas Y transfers energy to X, that we cannot define dS = dQ/T for a solute reaction without having any idea about the respective reversible process, and you would continue to believe that all this does not matter as long as supportive tests exist. Still let me describe one such test (although I have already described it many times). The derivation of the osmotic equation can be regarded as a successful test for thermodynamics - it is based on the free energy (chemical potential) concept. However, somewhere in the middle of the derivation, we should integrate dG = VdP /1/ in order to obtain delta G = V(Posm) /2/ The integration presupposes that V, the volume of the system, is constant - otherwise /2/ cannot be obtained at all. Since V is constant, both /1/ and /2/ correspond to a process in which no work of expansion is done. However there are other restrictions imposed on /1/ which reduce the respective physical process to absurdity. /1/ is obtained from dG = dQ + dW + PdV + VdP - TdS - SdT /3/ on the assumption that the process is REVERSIBLE (dQ = TdS), isothermal (dT = 0) and that ONLY WORK OF EXPANSION CAN BE DONE (dW = -PdV). However the integration is possible only if NO WORK OF EXPANSION IS DONE (dV = 0). Therefore, /1/ and /2/ in the derivation of the osmotic equation refer to a REVERSIBLE PROCESS IN WHICH NO WORK AT ALL IS DONE. In my opinion, this is a flagrant absurdity. The example is very typical. The osmotic equation is analogous to the ideal gas law - the analogy is straightforward both formally and physically, so an elegant derivation is possible based on simple thought experiments. However thermodynamics looks for "supportive" tests - here is the opportunity. The solute should no more be analogous to a gas - there should be no bombardment of any wall. Rather, it is the solvent that should move from a high to a low chemical potential. The derivation should be complicated and contain an obligatory for any delta G interpretation absurdity - this time it is a reversible process in which no work at all is done. Students should learn this and ask no respectless questions. Bryant, I would not be sorry if you neglect this example - I believe that a verification of a theory makes more sense if an alternative exists. So please revise your ultimatum "First the old tests, then new ones". I am not devising new tests - rather, I am trying to create a new paradigm allowing us to see all tests in a new light. This new paraigm includes defining what has not been defined so far, so even if it is wrong or you disagree, the discussion may prove useful. Let me start in the simplest possible way. The reaction A <-> B /4/ is at equilibrium. According to thermodynamics, no work can be extracted from it - it is like a massless object - no work is required to push it and, vice versa, it can push nothing. However /1/ can be coupled to another rection, e.g. C -> D: A + C -> B + D /5/ At the molecular level, as A and C react, we can expect either that A transfers energy to C or that C transfers energy to A. In both cases we can speak of MOLECULAR work, and in both cases this work moves /4/ away from equilibrium. So I see no reason to ignore a principle formulated suitably by Jonathan Marder: "WORK IS WHAT MOVES A CHEMICAL SYSTEM AWAY FROM EQUILIBRIUM". I see nothing wrong in an alternative thermodynamic theory based on this principle. It will just confirm some of the results of the old one, but at the same time will resolve some internal contradictions the old one possesses. This is a normal process, Bryant. No theory can be absolutely right, even thermodynamics. Best regards, Pentcho .