Review General Organic and Biological Chemistry 1 What

Review § General, Organic, and Biological Chemistry 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 Copyright © 2010 Pearson Education, Inc. 1

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… General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 2

Review 1) increase the internal temperature 2) does external work Ht added=↑ internal energy

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) General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 4

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

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

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

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 sources General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 8

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% General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 9

Lightbulbs § Incandescent lightbulbs are 3% efficient, fluorescent 10% …. miniheaters…. . CFLs (compact fluorescent lights) are 70 % efficient General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 10

3 rd major concept in the 2 nd law of Thermodynamics…Entropy General, Organic, and

Entropy- ordered energy tending to disordered energy For natural processes, entropy always increases General,

Entropy however, when there is work input (as in living organisms) entropy decreases General,

…. 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 General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 14

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 General, Organic, and Biological Chemistry 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 Copyright © 2010 Pearson Education, Inc. 15