CHEM 433 - 9/23/10

III. A. 1st Law of Thermodynamics (Chapter 2)

- 1st Law of THERMO (2.2)

- Expansion Work (2.3)

READ: Chapter #2

(Exam W – review sometime M or T?)

Work: dw = –Fdz

(A fancy way to say W = Force x distance… and that we have to integrate it if F changes over that distance)

Constant Pressure Expansion… w = –pextV

An indicator diagram = A graph of p(V), which displays work as the a “area under the curve”

Isothermal Reversible Expansion… w = –nRTln(V2/V1)

More work in this case: reversible system is pushing against maximum possible pressure…

An isotherm

Work for constant pressure case: w=-pextV