1. PHYS 1110 Lecture 11 Professor Stephen Thornton October 4, 2012

2. Reading Quiz What is peat? A)First stage of natural gas production. B)First stage of producing oil. C)First stage of producing coal. D)First stage of fossil fuel production. E)Name of terrestrial plants.

3. Reading Quiz What is peat? A)First stage of natural gas production. B)First stage of producing oil. C)First stage of producing coal. D)First stage of fossil fuel production. E)Name of terrestrial plants.

4. GO OVER MIDTERM EXAM

5. Various Engines http://www.animatedengines.com/ Look at Four Stroke Diesel Two Stroke Steam Locomotive Newcomen Atmospheric Engine Two Cylinder Stirling Engine http://www.animatedengines.com/

6. Entropy There are several ways to look at entropy, but eventually they are all equal. Entropy is related to disorder in a system. A messy bedroom has more entropy than a clean one. The natural order of the universe is to increase entropy. Your bedroom never naturally becomes clean; it always naturally becomes messy.

7. Entropy is also related to probability. There is a higher probability that a block of ice will melt at room temperature than it will get colder. Thermodynamics does not prevent either action. The probability of the latter is incredibly small.

8. Entropy is a very fundamental property, and is a state variable. It is determined by the heat flow Q divided by the temperature T.

9. For a reversible heat engine, the total entropy of the engine cycle is

10. Copyright © 2009 Pearson Education, Inc. Entropy and the Second Law of Thermodynamics The total entropy always increases when heat flows from a warmer object to a colder one in an isolated two-body system. The heat transferred is the same, and the cooler object is at a lower average temperature than the warmer one, so the entropy gained by the cooler one is always more than the entropy lost by the warmer one.

11. Copyright © 2009 Pearson Education, Inc. The fact that after every interaction the entropy of the system plus the environment increases is another way of putting the second law of thermodynamics: The entropy of an isolated system never decreases. It either stays constant (reversible processes) or increases (irreversible processes).

12. The total entropy of the universe increases whenever an irreversible process occurs. The total entropy of the universe is unchanged whenever a reversible process occurs. This is another way to state the 2 nd Law of Thermodynamics.

13. There is some really bad news here. Because the universe actually works through irreversible processes, the entropy is gradually increasing. There will eventually be a gradual “heat death” of the universe. The universe will be full of energy which cannot be used to perform work! We are doomed!

14. Order, Disorder, and Entropy As we have stated, entropy is related to disorder. As the entropy of a system increases, its disorder increases as well. GOOD NEWS: When you go home, and your mother fusses about how messy your bedroom is, tell her it is because entropy is increasing, and it is the natural order of the universe. There is little you or your mother can do about it (without doing a lot of work!). She will be impressed by how much physics you have learned!

15. Copyright © 2009 Pearson Education, Inc. Entropy is a measure of the disorder of a system. This gives us yet another statement of the second law: Natural processes tend to move toward a state of greater disorder. Example: If you put milk and sugar in your coffee and stir it, you wind up with coffee that is uniformly milky and sweet. No amount of stirring will get the milk and sugar to come back out of solution.

16. Copyright © 2009 Pearson Education, Inc. Another example: When a tornado hits a building, there is major damage. You never see a tornado approach a pile of rubble and leave a building behind when it passes.

17. Copyright © 2009 Pearson Education, Inc. Statistical Interpretation of Entropy and the Second Law The most probable distribution of speeds in a gas is Maxwellian: The most probable state is the one with the greatest disorder, or the greatest entropy. Highly unlikely

18. Copyright © 2009 Pearson Education, Inc. Statistical Interpretation of Entropy and the Second Law In this form, the second law of thermodynamics does not forbid processes in which the total entropy decreases; it just makes them exceedingly unlikely.

19. Copyright © 2009 Pearson Education, Inc. Thermal Pollution, Global Warming, and Energy Resources Over 90% of the energy used in the U.S. is generated using heat engines to drive turbines and generators—even nuclear power plants use the energy generated from fission to heat water for a steam engine. The thermal output Q L of all these heat engines contributes to warming of the atmosphere and water. This is an inevitable consequence of the second law of thermodynamics.

20. Conceptual Quiz In the closed thermodynamic cycle shown in the P-V diagram, the work done by the gas is: A) positive B) zero C) negative V P

21. Conceptual Quiz In the closed thermodynamic cycle shown in the P-V diagram, the work done by the gas is: A) positive B) zero C) negative The gas expands at a higher pressure and compresses at a lower pressure. In general, clockwise = positive work; counterclockwise = negative work. V P

22. Conceptual Quiz Conceptual Quiz Given your experience of what feels colder when you walk on it, which of the surfaces would have the highest thermal conductivity? A) a rug B) a steel surface C) a concrete floor D) has nothing to do with thermal conductivity

23. Conceptual Quiz Conceptual Quiz Given your experience of what feels colder when you walk on it, which of the surfaces would have the highest thermal conductivity? A) a rug B) a steel surface C) a concrete floor E) has nothing to do with thermal conductivity The heat flow rate is k A (T 1 − T 2 ) / L. All things being equal, bigger k leads to bigger heat loss. From the book: Steel = 40, Concrete = 0.84, Human tissue = 0.2, Wool = 0.04, in units of J/(s.m.C°).

24. Conceptual Quiz: Humpty Dumpty falls off and breaks. Can he get back together again? A) Yes, very easily. B) Yes, but with extremely low probability. C) No, there is no possibility. D) Are you kidding us? Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall; All the King's horses and all the King's men, Couldn't put Humpty together again.

25. Answer: B From what we just learned, this is only a question of probabilities. And no, I am not kidding!

26. Copyright © 2009 Pearson Education, Inc. Chapter 6 Fossil Fuels Fossil fuels include coal, oil (petroleum), and natural gas. Globally fossil fuels provide 81% of energy supply. Oil34% Coal27% Natural Gas21%

27. Copyright © 2009 Pearson Education, Inc. Countries using fossil fuels India82% China80% Mexico79% Italy79% … France8% Sweden4% Switzerland1%

28. Copyright © 2009 Pearson Education, Inc. Fossil fuels are formed in the geological past from plant or animal remains. Coal forms from layers of vegetation, but oil and gas form from marine organisms. The burning of fossil fuels releases carbon dioxide and other greenhouse gases that most scientists believe is one of the principal causes of global warming.

29. Copyright © 2009 Pearson Education, Inc. The use of coal continues to grow mostly due to China, while the market share of oil has dropped for more than a decade.

30. Oil bubbling out of ground from Beverly Hillbillies TV show.

31. The Middle East contains about 80% of known oil reserves if we do not include shale and tar sands. The area was covered by ocean 200 million years ago.

33. Peat is first stage of coal production. Still used in Ireland and Finland. Coal is most abundant fossil fuel found in USA.

34. Coal is classified into ranks. Only a little anthracite (Pa). Lots of bituminous in West Virginia, Kentucky, Pa. Sub-bituminous in Wyoming. Lignite in Texas and North Dakota. Higher ranks contain more carbon, which is important for energy content.

35. Left: coal with fossilized fern leaves. Bottom: coal bin.

36. Conceptual Quiz What is the most abundant fossil fuel found in the United States? A)Coal B)Natural gas C)Compressed natural gas D)Oil E)Gasoline

37. Conceptual Quiz What is the most abundant fossil fuel found in the United States? A)Coal B)Natural gas C)Compressed natural gas D)Oil E)Gasoline

38. Groups: History of fossil fuels. Iron making. Gas lighting. Modern era.