olegt
Posts: 1405
Joined: Dec. 2006
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The thread “No process can result in a net gain of information” underlies 2LoT is silly, and doubly so. First DLH picks up a paper from a third-rate physics teacher at a third-rate university (who publishes his stuff in the aforementioned silly journal Entropy), then the church choir sings variations of “Entropy is disorder."
Entropy does not equate disorder. This common misunderstanding has been discussed many times by physicists, but it isn't going away anytime soon. Consider this excerpt from an article published in the Journal of Chemical Education:
| Quote | To aid students in visualizing an increase in entropy many elementary chemistry texts use artists' before-and-after drawings of groups of "orderly" molecules that become "disorderly". This has been an anachronism ever since the ideas of quantized energy levels were introduced in elementary chemistry. "Orderly-disorderly" seems to be an easy visual support but it can be so grievously misleading as to be characterized as a failure-prone crutch rather than a truly reliable, sturdy aid.
After mentioning the origin of this visual device in the late 1800s and listing some errors in its use in modern texts, I will build on a recent article by Daniel F. Styer. It succinctly summarizes objections from statistical mechanics to characterizing higher entropy conditions as disorderly (1). Then after citing many failures of "disorder" as a criterion for evaluating entropy — all educationally unsettling, a few serious, I will urge the abandonment of order-disorder in introducing entropy to beginning students. Although it seems plausible, it is vague and potentially misleading, a non-fundamental description that does not point toward calculation or elaboration in elementary chemistry, and an anachronism since the introduction of portions of quantum mechanics in first-year textbooks. |
There are well-known examples of physical systems where the onset of order is accompanied by an increase in entropy. The great chemist Lars Onsager pointed out as early as in 1949 that the ordered (nematic) phase of hard, rod-shaped molecules has a higher entropy than the corresponding fully disordered phase. Peter Pusey explains in a recent Science perspective that a liquid of hard spheres freezes with an increase in entropy:
| Quote | The freezing transition of hard spheres was discovered by computer simulation in 1957 (3) and confirmed some 30 years later by experiments on colloidal suspensions (4). The transition is driven by entropy--paradoxically, the apparently ordered crystal has a higher entropy than the metastable fluid from which it grows, for example (5, 6)--and is controlled by just one variable, the concentration by volume, or volume fraction, of the particles in the suspension. As the concentration is increased, spheres in the fluid become increasingly crowded by their neighbors. By crystallizing, they gain more freedom for local motions: While ordered on the large scale, a crystal is locally disordered. Above the melting concentration (volume fraction 0.545) the entropy loss associated with large-scale ordering is more than offset by the entropy gain associated with increased local freedom.
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