General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review  1)What is the word for “movement of heat”? Thermodynamics 2) The phrase “energy cannot be created nor destroyed” is know as The law of conservation of energy 1

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review 3) What is the rest of the phrase (for the conservation of energy) ? It simply transforms into another form of energy 4) If you add energy to a system it does one of 2 things… 2

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review 1) increase the internal temperature 2) does external work Ht added=↑ internal energy + external work done 3

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. 2 nd Law of Thermodynamics- This is the one that prevents you from building a perpetual motion machine (motion that continues indefinitely without any external source of energy) 4

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. 2 nd Law of Thermodynamics Clausius Statement Kelvin-Planck Statement  This implies that it is impossible to build a heat engine that has 100% efficient heat engine 5

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Changing Work (Fxd) Completely Into Heat is Easy  1) Rub your hands together quickly  2) Push a box across the floor 6

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Changing Heat Completely Into Work (Fxd) Can Never Happen  The best that can happen is to convert some heat into mechanical work 7  The first steam engine to do this was invented in 1700

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Engines and the 2 nd Law Today steam turbines generate about 90% of the electric power in the United States using a variety of heat sourcessteam turbines electric power 8

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Engines and the 2 nd Law  The average automobile engine is only about 35% efficient, and must also be kept idling at stoplights, wasting an additional 17% of the energy, resulting in an overall efficiency of 18% 9

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Lightbulbs  Incandescent lightbulbs are 3% efficient, fluorescent 10% ….mini- heaters…..CFLs (compact fluorescent lights) are 70 % efficient 10

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. 3 rd major concept in the 2 nd law of Thermodynamics…Entropy 11

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Entropy- ordered energy tending to disordered energy For natural processes, entropy always increases 12

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Entropy however, when there is work input (as in living organisms) entropy decreases 13

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. ….in a nutshell-the 2 nd Law of Thermodynamics  1) Heat flows from a hot body to a cool one  2) Heat cannot be completely converted to work  3) Every system becomes disordered over time 14

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. The laws of thermodynamics are sometimes stated this way 1) You can’t win 2) You can’t break even 3) You can’t get out of the game 1) b/c you can’t get any more energy out of a system than you put in 2) b/c you can’t even get as much energy out as you put in 3) Entropy in the universe is always increasing 15