The physical description of elementary surface phenomena: Thermodynamics versus mechanics
作者:
Julio Pellicer,
José A. Manzanares,
Salvador Mafé,
期刊:
American Journal of Physics
(AIP Available online 1995)
卷期:
Volume 63,
issue 6
页码: 542-547
ISSN:0002-9505
年代: 1995
DOI:10.1119/1.17866
出版商: American Association of Physics Teachers
关键词: SURFACE PROPERTIES;THERMODYNAMICS;SURFACE ENERGY;FREE ENERGY;SURFACE TENSION;PHASE BOUNDARIES
数据来源: AIP
摘要:
A unified treatment of elementary surface phenomena based on the formalism of thermodynamics is presented and compared to more familiar treatments based on the formalism of Newtonian mechanics. Emphasis is put on the surface free energy concept rather than on surface tension, not only because the former is more fundamental, but also because the latter may mislead if pushed too far. The examples discussed (Young–Laplace and Young–Dupré equations, and capillary rise) can be easily described with the help of the Helmholtz function, and clearly show some of the advantages of the thermodynamic approach. In particular, several misleading results appearing in elementary treatments can be avoided by using this approach. It is concluded that: (i) thermodynamics and physical chemistry courses should favor the formalism of thermodynamics rather than mechanics when dealing with surface phenomena; and (ii) when the mechanical approach is still preferred, some weak points in the standard derivations (e.g., the existence of an adhesion force in the explanation of the Young–Dupré equation and the nature and balance of forces in capillary rise) should be properly dealt with.
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