1. Announcements 2/2/11 Exam review session (tentative): Friday, 3-4:30 pm a. a.I will send email tomorrow with final date/time, and room location. (Vote today if you haven’t yet!) Reading assignment for Friday: a. a.Section 22.8 – Especially the marble example (Ex. 22.7, in my edition), but not the “Adiabatic Free Expansion: One Last Time” example (Ex. 22.8, in my edition). b. b.The “What is entropy?” handout posted to website – Read up through Example 1. Please spend at least ~10 minutes glancing over it, or you will likely be really confused in class on Friday.

2. Reading quiz Which of the following is a version of the Second Law of Thermodynamics? a. a.The entropy of any system decreases in all real processes b. b.The entropy of any system increases in all real processes c. c.The entropy of the Universe decreases in all real processes d. d.The entropy of the Universe increases in all real processes

3. Time for some physics humor Xkcd comic: Thermodynamics song: a. a.http://www.uky.edu/~holler/CHE107/media/first_second_law.mp3http://www.uky.edu/~holler/CHE107/media/first_second_law.mp3

4. Second Law Clausius: Heat spontaneously flows from hot to cold, not the other way around Why? Order. Which hand is more likely?

5. Microstates vs Macrostates Hand on left a. a.microstate = A spades, K spd, Q spd, J spd, 10 spd b. b.macrostate = ? c. c.How many microstates make up that macrostate? Hand on right a. a.microstate = 2 spades, 3 diam, 7 heart, 8 clubs, Q diam b. b.macrostate = ? c. c.How many microstates make up that macrostate? The most common macrostates are those that…

6. Probability  Heat flow You separate a deck into two halves: one is 70% red, 30% black; the other is 30% red, 70% black. What will happen if you randomly exchange cards between the two?

7. Thermodynamics For the air in this room, right now: a. a.Microstate = ? b. b.Macrostate = ? Hold this thought until Friday

8. A New State Variable State variables we know: P, V, T, E int Observation: doesn’t depend on path  Something is a state variable! Assumption: path is well defined, T exists whole time  “Internally reversible” A B P V

9. “Proof” by example, monatomic gas Path 1: A  C  B Path 2: A  D  B (D  B = isothermal) A B P V C D V1V1 2V 1 4V 1 P1P1 2P 1 Path 1: A  C + C  B Path 2: A  D + D  B Equal?

10. Entropy: S Assume S = 0 is defined somewhere. (That’s actually the Third Law, not mentioned in your textbook.) Integral only defined for internally reversible paths, but… S is a state variable! …so it doesn’t matter what path you use to calculate it! Advertisement: On Friday I’ll (try to) explain how/why this quantity is related to microstates & macrostates

11.  S for “free expansion” What is V 2 ? T 2 ? P 2 ? How to find  S?  S for adiabatic? Adiabats as constant entropy contours (“isentropic” changes) Wait… isn’t “free expansion” an adiabatic process? beforeafter

12.  S for isothermal?  S for const. volume?  S for const. pressure?

13.  S of Universe  S of gas doesn’t depend on path (state variable): What about  S of surroundings? What about  S total =  S gas +  S surroundings ? A B P V (See HW problem 12-4)