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This 1 page Class Notes was uploaded by Giovanna Torp on Monday September 28, 2015. The Class Notes belongs to MSE260 at University of Pennsylvania taught by Staff in Fall. Since its upload, it has received 14 views. For similar materials see /class/215421/mse260-university-of-pennsylvania in Materials Science&Engineering at University of Pennsylvania.
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Date Created: 09/28/15
Key terms 3rel Law 0ftherm0dynamics 3 law T 9 K S 0 and CP CV 0 only true for homogeneous samples in complete internal equilibrium Entropies Because S 0 at 0 K can calculate absolute entropies of materials Tabulated data lists S at 298K Standard entropy given by symbol S T for gases implies at one atm for solidsliquids implies pure amp at 1 atm S at some other T calculated using T S T S0298K JCpTdT 298 However if the material undergoes a phase change between 298K and the T of interest then the entropy of the phase change must be included and the heat capacity for the appropriate phase should be used e g material undergoing 91 transition at 1073K want S at 1400K 1073 1400 501400 2 S0298K mmDar Asomem1073 cWDdr 298 1073 Enthalpies Because H 3 0 at 0 K do not know absolute values of H T Define standard state at 298K H 298 0 for pure stable form of all elements Values of H 298 for all other materials measured relative to this T HOT H0298 J deT 298 Phase changes treated same way as above e g for the example above 1073 H01400 H0298K Camude AH meMO73 Guitar 298 1073 Free energies calculate H T and S T and then use G T H T TS T Heat capacity data for materials experimental data for Cp is given by a polynomial of the type CpabTcT392 a b c are empirical constants listed in tables of data All integrations involving Cp should account for the T dependence