Paperwork Today –Problems ch.20 –?’s Friday –Guest Lecture to Kick off Ch. 21 What are on quizzes? –Seriously – Read chapter (Yellow!)

Lab 3 Thoughts Exemplified heat engine processes Quantitative analysis of work done

Entropy Question A 740 g quantity of an ideal gas undergoes a reversible isothermal compression at a temperature of 330 K. The compression reduces the volume of the gas from 0.40 m 3 initially, to 0.32 m 3 finally. The molecular mass of the gas is 320 g/mol. The entropy change for the gas, in SI units, is ? Entropy, Ideal Gas, Energy Tools:

First Thought Entropy Change positive or negative? Is it zero? Why do we usually talk about  S & not S?

2 nd thought Parameters Initial Final Tools

What are constants? Temperature? –Yes 330 K Mass (Moles)? –Yes: Mass = 740 g & M.M. = 320 g/mol –# moles = –n = 2.31 moles Volume? –No: Goes from 0.4 to 0.32 m 3. Pressure? –No: Increases Heat? –No. dQ = dU + dW –dQ = dW, dW not likely zero with volume change Fill in previous page, Follow main entropy Equation Next

Fill in & Follow Thru Parameters (SI UNITS): R=8.31 Initial –V1 = 0.4n1 = 2.31T1 =330 –p1 = (nRT)/V = Final –V2 = 0.32n2 = 2.31T2 =330 –p2 = (nRT)/V = Tools

Equation Fun Isothermal Implications

Equation Fun Insert Ideal Gas Constraint Entropy Units? Why not use: dQ = nCdT?

Make Random Engine Make p-V Diagram Calculate Work Done, Entropy Constraints Ideal Gas c V = 3R/2, C P = 5R/2 (monotomic) For Each Cycle: Something Constant Tools

Friday Guest Lecture Ch. 21