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Unformatted text preview: MSE 3050, Thermodynamics and Kinetics of Materials, Leonid Zhigilei Heat Capacity The heat capacity, C, of a system is the ratio of the heat added to the system, or withdrawn from the system, to the resultant change in the temperature: C = q/ T = q/dT [J/deg] This definition is only valid in the absence of phase transitions Usually C is given as specific heat capacity , c, per gram or per mol New state of the system is not defined by T only, need to specify or constrain second variable: V V dT q C = P P dT q C =- heat capacity at constant volume- heat capacity at constant pressure The fact that q is not a state function and depends on the path is reflected in the dependence of the heat capacity on the path, c p c v (note that small c is used for the derived intensive quantity, per mass, per volume, or per mole, versus capital C for the extensive quantity. For a system containing n moles C p = nc p and C v = nc v where c p and c v are molar values). c V and c P can be measured experimentally isobaric process: dH = q = c P dT isochoric process: dU = q = c V dT H and U can be calculated from c P and c V MSE 3050, Thermodynamics and Kinetics of Materials, Leonid Zhigilei c v vs. c p If material is allowed to expand during heating, how this affects its heat capacity?...
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- Spring '12