Ch04

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Ch04

  1. 1. Heat and the Second Law of Thermodynamics Chapter 4 Great Idea: Heat is a form of energy that flows from warmer to cooler objects
  2. 2. Chapter Outline <ul><li>Nature’s Direction </li></ul><ul><li>Coming to Terms with Heat </li></ul><ul><li>Heat Transfer </li></ul><ul><li>The Second Law of Thermodynamics </li></ul><ul><li>Consequences of the Second Law </li></ul>
  3. 3. Nature’s Direction
  4. 4. Nature’s Direction <ul><li>First Law of Thermodynamics </li></ul><ul><li>Tendency for disorder </li></ul><ul><li>Evolution to a more probable state </li></ul>
  5. 5. Second Law of Thermodynamics
  6. 6. Coming to Terms with Heat
  7. 7. Heat and Temperature <ul><li>Heat </li></ul><ul><ul><li>Energy in motion </li></ul></ul><ul><ul><li>Warm to cool </li></ul></ul><ul><li>Temperature </li></ul><ul><ul><li>Atomic movement </li></ul></ul><ul><li>Temperature Scales </li></ul><ul><ul><li>Fahrenheit scale </li></ul></ul><ul><ul><li>Celsius </li></ul></ul><ul><ul><li>Kelvin </li></ul></ul><ul><ul><ul><li>Absolute zero </li></ul></ul></ul>
  8. 8. Comparison of Temperature Scales
  9. 9. Temperature Conversions <ul><li>Conversion to Fahrenheit: </li></ul><ul><ul><li>°F = (1.8 x °C) + 32 </li></ul></ul><ul><li>Conversion to Celsius: </li></ul><ul><ul><li>°C = (°F – 32)/1.8 </li></ul></ul>
  10. 10. Early Thermometer – 1600s
  11. 11. Specific Heat Capacity <ul><li>Specific heat capacity </li></ul><ul><ul><li>Quantity of heat needed to raise 1g of a substance by 1 °C </li></ul></ul><ul><li>Water </li></ul><ul><ul><li>Highest specific heat </li></ul></ul><ul><ul><li>1 cal/g °C </li></ul></ul>
  12. 12. Heat Transfer
  13. 13. Heat Transfer <ul><li>Conduction </li></ul><ul><ul><li>Movement of heat by atomic-scale collision </li></ul></ul><ul><ul><li>Thermal conductivity </li></ul></ul><ul><li>Convection </li></ul><ul><ul><li>Bulk transfer of molecules </li></ul></ul><ul><ul><li>Convection cell </li></ul></ul><ul><li>Radiation </li></ul>
  14. 14. Conduction
  15. 15. Infrared Imaging Detects Heat Loss
  16. 16. Convection
  17. 17. Convection Cells in the Air
  18. 18. Technology <ul><li>Home Insulation </li></ul>
  19. 19. The Science of Life <ul><li>Animal Insulation and Feathers </li></ul>
  20. 20. The Science of Life <ul><li>Temperature Regulation </li></ul>
  21. 21. The Second Law of Thermodynamics
  22. 22. The Second Law of Thermodynamics <ul><li>3 Statements of the Law </li></ul><ul><ul><li>Heat does not flow spontaneously from cold to hot </li></ul></ul><ul><ul><li>No engine can exclusively convert heat to work </li></ul></ul><ul><ul><li>Every isolated system tends toward disorder </li></ul></ul>
  23. 23. Heat Will Not Flow Spontaneously from a Cold to a Hot Body <ul><li>Molecular level </li></ul><ul><ul><li>Faster object shares energy </li></ul></ul><ul><li>Energy required </li></ul><ul><ul><li>To cool an object requires energy </li></ul></ul>
  24. 24. You Cannot Construct an Engine that Does Nothing but Convert Heat to Useful Work <ul><li>Efficiency </li></ul><ul><li>High- to Low-temperature reservoirs </li></ul>
  25. 25. Efficiency of an Engine <ul><li>Determined by the second law of thermodynamics </li></ul>
  26. 26. Every Isolated System Becomes More Disordered with Time <ul><li>Ordered System </li></ul><ul><ul><li>Regular predictable pattern </li></ul></ul><ul><li>Disordered System </li></ul><ul><ul><li>Random </li></ul></ul><ul><li>Entropy </li></ul><ul><ul><li>Measure of disorder </li></ul></ul><ul><ul><li>The entropy of an isolated system remains constant or increases </li></ul></ul>
  27. 27. Highly Ordered Regular vs. Disordered Patterns
  28. 28. Hundreds of Arrangements
  29. 29. Consequences of the Second Law
  30. 30. The Arrow of Time <ul><li>Four dimensions </li></ul><ul><ul><li>3 have no directionality </li></ul></ul><ul><ul><li>The 4 th has direction </li></ul></ul><ul><li>Time </li></ul><ul><ul><li>Second law and time </li></ul></ul>
  31. 31. Built-in Limitations of the Universe <ul><li>The Second Law’s consequences </li></ul><ul><ul><li>Some things cannot happen </li></ul></ul><ul><ul><li>Fossil fuels </li></ul></ul><ul><ul><li>Hierarchy of energy </li></ul></ul>
  32. 32. The Science of Life <ul><li>Evolution and the Second Law of Thermodynamics </li></ul>

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