CCL: New Blog on how NOT to teach Le Chatelier's Principle

 Sent to CCL by: "Alavi, Saman" [Saman.Alavi-#-nrc-cnrc.gc.ca]
 There are many interesting articles and a fascinating history of the controversy
 surrounding the applicability of Le Chatelier's principle. The arguments are
 quite old, but make for very instructive reading. Some references are:
 B. Singh and D. Ebbing, "Le Chatelier's Theorem", Journal of Chemical
 Education, 33, 34 (1956)
 J. de Heer, "The principle of Le Chatelier and Braun", Journal of
 Chemical Education, 34, 375 (1957)
 A. Standen, "Le Chatelier, common sense, and metaphysics", Journal of
 Chemical Education, 35, 132 (1958)
 J. de Heer, "Le Chatelier, scientific principle, or sacred cow",
 Journal of Chemical Education, 35, 133 (1958)
 J. Gold and V. Gold, "Neither Le Chatelier's nor a principle?",
 Chemistry in Britain, 802 (September 1984)
 Even Paul Ehrenfest contributed to the discussion at some stage.
 Thermodynamically, this principle is not of much use and can be replaced by more
 exact mathematical formulations. Gold and Gold state that it lives on in General
 Chemistry books as a qualitative rule of thumb which is supposed to bring order
 to many diverse chemical phenomena. Its possible mis-application and numerous
 caveats which must be satisfied before it holds can be good arguments against
 including it in General Chemistry courses. However, the mystique surrounding
 such general rules and why they should apply may be a attractive to instructors
 and students.
 Saman
 ________________________________________
 > From: owner-chemistry+saman.alavi==nrc.ca[*]ccl.net
 [owner-chemistry+saman.alavi==nrc.ca[*]ccl.net] On Behalf Of VITORGE Pierre
 094605 Pierre.VITORGE*o*cea.fr [owner-chemistry[*]ccl.net]
 Sent: July 8, 2012 4:28 PM
 To: Alavi, Saman
 Subject: CCL: New Blog on how NOT to teach Le Chatelier's Prtinciple
 Sent to CCL by: VITORGE Pierre 094605 [Pierre.VITORGE .. cea.fr]
 Could you first go back to the original citation of Le Chatelier's principle?
 Henri Le Chatelier, « Sur un énoncé général des lois
 des équilibres chimiques », dans C.R. Hebd. Seances Acad. Sci., vol.
 99, 1884, p. 786-789 (ISSN 0001-4036) http://gallica.bnf.fr/ark:/12148/bpt6k3055h.image.f786.pagination.langFR
 The article is a discussion "of the laws of chemical equilibria" under
 the influence of various parameters that can shift chemical equilibria, Le
 Chatelier cites other authors that had already found such laws for some
 parameters: Le Chatelier proposed that it is actually valid for any parameter.
 He gives many examples. In one of them he wrote
 "si elle se produisait seule"
 which means that if you vary a parameter all the other ones should be kept
 constants for the reasoning
 He did not re-write "si elle se produisait seule" for each example,
 but it is obvious that he discussed or illustrated parameters one by one.
 As a consequence your objection with the 3H2 + N2 <-> NH3 exemple might
 rather be originated in a problem of translation or misunderstanding of the
 original publication
 In your blog you used the law of mass action (which is indeed a later
 quantitative illustration of Le Chatelier's principle) for the above example:
 this give uselessly complicated calculations, while the application of Le
 Chatelier's principle is essentially based on the comparison of 4 moles (3H2 +
 N2) with 1 mole (NH3).
 --
 Pierre Vitorge
 Directeur de recherche CEA
 Laboratoire Analyse et Modelisation pour la Biologie et l Environnement, LAMBE,
 UMR 8587, CEA, Univ Evry, CNRS,
 http://www.lambe.univ-evry.fr/pvitorge
 http://www.vitorge.name
 --
 Laboratoire de Radiolyse et de la Matiere Organique, LRMO
 CEA, DEN, Saclay, DPC, SECR,
 -----Message d'origine-----
 De : owner-chemistry+pierre.vitorge==cea.fr*_*ccl.net [mailto:owner-chemistry+pierre.vitorge==cea.fr*_*ccl.net] De la part de
 Guntram Schmidt guntram.schmidt^^chemie.uni-halle.de
 Envoyé : samedi 7 juillet 2012 23:48
 À : VITORGE Pierre 094605
 Objet : CCL: New Blog on how NOT to teach Le Chatelier's Prtinciple
 Sent to CCL by: Guntram Schmidt [guntram.schmidt.*_*.chemie.uni-halle.de]
 Now that's the right way to frighten off students!
 Instead of explaining things to the students, give them a very abstract
 mathematical formula without a strong relation to the outer world and
 let them analyze this...
 Do you think, this will help them UNDERSTANDING the principles of nature?
 If I were your student, I would ask about the meaning of a "division
 operation" in nature, how you dare to assign numbers to not counted
 (non-countable?) entities, questioning the whole measure theory itself
 (which is still an unanswered question)...
 I believe that with chemistry, we have the rare chance to teach natural
 sciences on the basis of easy, handmade experiments - lets try to keep
 having this edge over physics and biology!
 You asked for comments ;-),
 Guntram
 Am 07.07.2012 16:29, schrieb Eric Scerri scerri:-:chem.ucla.edu:
 >
 > http://eric1scerri.blogspot.com/
 >
 > Comments welcome.
 >
 > regards,
 > eric scerri
 >
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