2300_les10 - III. Properties of Pure Substances I. Specific...

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1 lesson 10 III. Properties of Pure Substances I. Specific Heats 1. We can’t directly measure changes in internal energy, u, but we can measure changes in T and v. The change in u is proportional to the change in temperature, u T. a. For a pure substance, it is convenient to let u = f(T,v) b. Then in a closed system at constant volume , c. Define specific heat at constant volume as d. In words: c v is the thermal energy required to raise the temperature of 1 kg by 1 degree K or C at constant volume. 2 1 T vv v , a v e 2 1 T du c dT or U m c (T )dT or U mc ( TT ) ∆∆ == = v v uk J c Tk g K ⎛⎞ = ⎜⎟ ⎝⎠ Temperature unit is temperature difference. (4-19) lesson 10 III. Properties of Pure Substances 2. We can’t directly measure changes in enthalpy, h, but we can measure changes T and p. The change in h is proportional to the change in temperature, h T. a. For a pure substance, it is convenient to let h = f(T,p) b. Then in a closed system at constant pressure , c. Define specific heat at constant pressure as d. In words: c p is the thermal energy required to raise the temperature of 1 kg by 1 degree K or C at constant pressure. p p hk J c g K = Temperature is temperature difference.
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2300_les10 - III. Properties of Pure Substances I. Specific...

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