5_60_lecture2

# 5_60_lecture2 - MIT OpenCourseWare http:/ocw.mit.edu 5.60...

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MIT OpenCourseWare http://ocw.mit.edu 5.60 Thermodynamics & Kinetics Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .

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5.60 Spring 2008 Lecture #2 page 1 Work, Heat, and the First Law Work: w = F A applied force distance A Expansion work = p ext A p ext ext p =− ( A ) A ext V convention: Having a “-“ sign here implies > 0 if < 0 , that is, positive work means that the surroundings do work to the system. If the system does work on the surroundings ( > 0 ) then < 0 . If ext is not constant, then we have to look at infinitesimal changes d - = − dV d - means this is not an exact differential Integral 1 2 depends on the path!!! Path dependence of Example: assume a reversible process so that ext = p Ar (g, 1 , V 1 ) = Ar (g, 2 , 2 ) Compression 1 > 2 and 1 < 2
5.60 Spring 2008 Lecture #2 page 2 p ext =p 1 p ext 2 compression ,V p 11 initial Two paths: (1) First V 1 2 at p = 1 then 1 2 at = 2 Ar(g, 1 , 1 ) = Ar(g, 1 , 2 ) = Ar(g, 2 , 2 ) p final p 2 (2) p 1 init. (1) ,V p 22 final (2) First 1 2 at = 1 then 1 2

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## This note was uploaded on 07/31/2011 for the course CHM 170 taught by Professor Lemtayo during the Spring '11 term at MIT.

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5_60_lecture2 - MIT OpenCourseWare http:/ocw.mit.edu 5.60...

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