Lon-Capa 4 th HW assignment due today, 5 pm. 3 rd Quiz due Sunday, 10/12 by 10 pm. It will open today at 5 pm. 5 th HW assignment is also open! 1

2 Clicker Question Consider an ideal gas in a container fitted with a piston. A weight is added to the piston. What is true about ΔS? ΔS is: a) positive (entropy of the system increases). b)negative (entropy of the system decreases). c) zero (entropy of the system doesn’t change). d) More information is needed to determine this. e) I do not know.

3 Laws of Thermodynamics First Law The quantity of energy is conserved. “You cannot win, you can only break even.” Second Law The quality of energy is not conserved. It’s usefulness decreases. “You cannot break even.”

4 Clicker Question Consider two containers each filled with 1.0 mol of an ideal gas (same P, V, T). One container is a rigid steel tank, the other fitted with a piston. You transfer the same amount of energy as heat to each container. Which gas has the higher final temperature? a) The gas in the rigid steel container. b) The gas in the container fitted with a piston. c) The gases have the same final temperature. d) I do not know.

5 Ideal and Real: C P – C V = R

6 A Question to Consider… You have 1.0 mol of an ideal monatomic gas. It is taken from State A (P A = 10.0 atm and V A = 2.00 L) to State B (P B = 5.00 atm and V B = 4.00 L) by two different pathways: Pathway I: Constant P to 4.00 L, then constant V to 5.00 atm. Pathway II: Constant V to 5.00 atm, then constant P to 4.00 L. Determine ΔH, ΔE, q, w for each step and overall.

7 Your Question to Consider I have added another “PV diagram” type question (this time P A V A ≠ P B V B ) as a PDF. Please work on this on your own and ask questions if you have them (of me or your TA). I have included answers and brief explanations (but don’t peek too early!).