COP Refrigerators and Heat Pumps

1. COP Refrigerators and Heat Pumps

3. Reverse World http://www.youtube.com/watch?v=EahHThBjDB0

4. Test 2 • Starts Friday Oct 18 • Ends Monday Oct 21 • Late day Tuesday Oct 22 • 16 Multiple Choice • 4 Free Response • Give yourself plenty of time!

5. Entropy is a measure of disorder… • But what does that mean?

6. Micro vs Macro States

7. Entropy is about probability.It is very improbable that we will ever observe a process that decreases the entropy of a real physical process. In the limit as N goes to infinity, probability becomes fact. Consider the air in this room.

8. Entropy – it’s different things to different people • Information (compression) • Parking a Car • Clutter • Thermodynamic • Quantization

9. Reversible vs. Irreversible • Irreversible • Free expansion (adiabatic-ish) • Heat conduction • Scrambling Eggs, Bar room fight • Reversible • Adiabatic expansion • Constant T expansion (at least for the gas) • Ice melting (sort of) • Isolated vs Open Systems

10. Water runs over a waterfall. What kind of process is this? • Reversible • Irreversible

11. Reversible process - one that works equally well in reverse, one whose effect you can undo • Irreversible process - one you cannot undo or will not spontaneously run in reverse • Pretty much all spontaneous events in nature are irreversible • irreversiblereversible • scrambling eggsice  liquid at 0oC • eating fish liquid  steam at 100oC

12. Puff Balls Law of Increasing Disorder(2nd Law of Thermodynamics) Changes occurring in natural systems always proceed in such a way that the total amount of disorder in a closed system never decreases, and it increases in irreversible processes. http://www.youtube.com/watch?v=X4zd4Qpsbs8&NR=1

13. 2 Ne 9:28 O that cunning plan of the evil one! O the vainness, and the frailties, and the foolishness of men! When they are learned they think they are wise, and they hearken not unto the counsel of God, for they set it aside, supposing they know of themselves, wherefore, their wisdom is foolishness and it profiteth them not. And they shall perish.

14. Increase in Entropy = Increase in disorder

15. Ice Melting

16. Isothermal Expansion

17. A B Which path has a larger ∆S • The same • Not enough information

18. Quick Quiz 22.6 The entropy change in a free expansion must be zero because Q=0 A. True B. False

19. Non-reversible ideal gas process Any path will do. Pick one you can calculate!

20. If an ideal gas undergoes a non-reversible process, which of the following will be true? • The entropy will increase • The entropy will decrease • The entropy will stay the same • It depends

21. Free expansion The change in entropy for a free expansion is • Positive • Negative • Zero • I do not know

22. Free expansion

23. Free expansion followed by isothermal compression

24. Conduction HOT COLD Ordered WARM Disordered

26. Universal Heat Death “This is the way the world ends, not with a bang but a whimper.” T.S. Eliot

27. Gospel perspective "every thing restored to its perfect frame" Alma 11:44