Variation of entropy and volume of liquids with pressure and their Kauzmann- and Simon-type extrapolations toward zero entropy
| Autor: | G. P. Johari |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Physics
Enthalpy Extrapolation Thermodynamics 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Heat capacity Isothermal process 010406 physical chemistry 0104 chemical sciences Entropy (classical thermodynamics) Volume (thermodynamics) Physical and Theoretical Chemistry 0210 nano-technology Supercooling Instrumentation Third law of thermodynamics |
| Zdroj: | Thermochimica Acta. 700:178936 |
| ISSN: | 0040-6031 |
| DOI: | 10.1016/j.tca.2021.178936 |
| Popis: | Variation of the entropy of a liquid, Sliq, with temperature, T, and its extrapolation to T below the glass formation temperature are used as a basis for advancing theories of glass-formation. A liquid may be transformed into a glass also by pressurizing at a fixed T. In such cases, one needs to know how Sliq varies with the applied pressure, P. But plots of Sliq against P are rarely reported, because it is difficult to measure the heat capacity under a high pressure over a wide range of T from near 0 K needed to determine the variation of Sliq with P. Here we employ an alternative approach by using the available data for the variation of volume, Vliq, with T and P, and thus obtain the plots of Δ S l i q = S l i q − S 0 0 against P, where S 0 0 is the entropy at 0 K. As examples, we consider the melt states of polystyrene and poly(ortho-methylstyrene). We then compare the extrapolation of the ΔSliq and Vliq plots against P at fixed T against the extrapolation of the ΔSliq and Vliq plots against T at 1 bar pressure, and provide criteria that may be used to determine merits of the extrapolation of the excess entropy of the liquid over the crystal state at 1 bar pressure, as envisaged by Simon (Z. Anorg. Allg. Chem. 203 (1931) 219–227), by Kauzmann (Chem. Rev. 43 (1948) 219–256), and as quantitatively described within the precepts of the third law of thermodynamics along with the excess enthalpy (G. P. Johari, J. Chem. Phys. 113 (2000) 751–761). We conclude that when a liquid is isothermally pressurized above its freezing pressure, ΔSliq would asymptotically approach zero, and Vliq would similarly approach its limiting low value. This is analogous to the approach of ΔSliq and Vliq when a liquid is isobarically supercooled. |
| Databáze: | OpenAIRE |
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