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Unformatted text preview: Specific Heat of Diatomic Gases and Solids The Adiabatic rocess Process Lecture 7 Specific Heat for Solids and Diatomic Gasses In this lecture, you will learn what determines the specific heat of diatomic gasses and elemental solids. The physics behind an adiabatic gas process will also be analyzed. From last lecture, you learned how to evaluate the heat capacity for an ideal monatomic gas The internal energy of N atoms in an ideal monatomic gas is an intrinsic, distributed property of the system ( 29 2 1 1 ( ) 2 2 av av av KE K m v kT for one molecule = = = 3 E int KE = 3 ( NkT) = 3 ( nRT) What makes diatomic molecules different? dE int dT C V = 3/2 nR C P = C V + nR = 5/2 nR equipartition theorem For ideal gas of N atoms: monatomic gas Velocity v Mass m r Rotational motion  another way to distribute energy? (rad/s) For now, no linear translation KE = mv 2 = 2 f v = r KE = mr 2 2 = I 2 Typical value: CO, I 1.45 x 1046 kgm 2 Linear Motion Rotational Motion Inertia Newtons 2 nd Law m F = m a I = I By way of review, . . . Displacement Velocity d = v o t+ at 2 = o t + t 2 v = v o + at = o + t Momentum Conservation of momentum Kinetic Energy p = mv If F=0, then p = constant mv 2 L = I If =0, then L = constant I 2 For diatomic molecules, additional energy can be disbursed in rotational motion KE = mv x 2 + mv y 2 + mv z 2 + I x x 2 + I y y 2 E int = 5 ( nRT) C v = 5/2 nR C P = 7/2 nR translation + rotation 5 degrees of freedom Work Done = Change in Elastic Energy...
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This note was uploaded on 04/23/2011 for the course PHYS 242 taught by Professor Staff during the Spring '08 term at Purdue UniversityWest Lafayette.
 Spring '08
 Staff
 Heat

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