8 Thermo 5

# 8 Thermo 5 - Constant volume (isochoric) process V = const....

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Unformatted text preview: Constant volume (isochoric) process V = const. = V P W Q U = n number of moles of the gas; C v molar specific heat at constant volume heat capacity of one mole of the gas in a constant-volume process. T mc Q = (Compare with ) Why bother introducing a new parameter? T nC U v = Measuring C v we learn about internal energy of the gas as a function of temperature! W Q U = T nC Q v = ) /( T n Q C v Heat is energy in transit! Internal energy relates to the energetic content of an object or a system. Whereas Heat is energy in transit! More specifically, the heat, Q , relates to the energy transferred due to temperature difference alone . While, W , incorporates all other sorts of energy transfer, most commonly mechanical work . The amount of heat transferred to a system, Q , is a characteristic of the specific process in which it is transferred. Consequence: heat capacity and molar specific heat of ideal gas are characteristics of the process in which heat is transferred. T Q C = / ) /( T n Q C molar = Is the change in internal energy going to be the same? Is work going to be the same for different processes? Multiple ways to get (quasi-statically !) from an initial to a final stateE Is heat going to be the same? Internal energy is a function of state and will be the same as well as it variation between the states. NO! YES! NO! W Q U = V P From the 1 st law and equation for C v : V P W = What about internal energy and heat? W Q U = nRT PV = V P T nC W U Q v + = + = Ideal gas at constant pressure: T nR V P = T R C n T nR T nC W U Q v v + = + = + = ) ( Molar specific heat at constant pressure (definition): ) /( T n Q C p = T R C n T nC v p + = ) ( R C C v p + = Constant pressure (isobaric) V P From the 1 st law and equation for C v : T R C n V P T nC W U Q v v + = = + = = + = ) ( Molar specific heat at constant pressure (definition): T nC Q p = R C C v p + = Why is specific heat at constant pressure higher than at constant volume?Why is specific heat at constant pressure higher than at constant volume?...
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## This note was uploaded on 12/13/2011 for the course PHYS 2C PHYS 2C taught by Professor Groisman during the Spring '11 term at UCSD.

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8 Thermo 5 - Constant volume (isochoric) process V = const....

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