1. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Processes  A key concept in the study of thermodynamics  http://footage.shutterstock.com/clip-1505705-stock- footage--d-animated-visualization-of-car-engine- piston-work-loop.html http://footage.shutterstock.com/clip-1505705-stock- footage--d-animated-visualization-of-car-engine- piston-work-loop.html 1

2. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. What’s in a name?  Adiabatic means “without passage or impassable”. (Greek)  Refers to the absence of transfer of energy in the form of heat 2

3. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Definition- a process when no heat enters or leaves the system (atoms to universe) This can be achieved in either 1)Performing the process rapidly or 2)By insulating a system from its surroundings (for example styrofoam) 3

4. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Heating-occurs when gas is compressed (work in done on the system by its surroundings) the piston in a cylinder…gas engines move the pistons so fast, up and down, that they don’t generate enough heat, so they rely on spark plugs to ignite the fuel, but diesel engines use high compressions so they ignite the fuel w/o spark plugs  http://www.youtube. com/watch?v=dQeC EqkE9eE http://www.youtube. com/watch?v=dQeC EqkE9eE 4

5. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Heating-occurs when gas is compressed (work in done on the system by its surroundings  A chinook wind- blows down the Rocky Mountains across the Great Plains. Cold air moves down the slopes and becomes compressed b/c of increased pressure 5

6. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Heating-occurs when gas is compressed The key concept then is that when a gas is compressed, the gas gains energy and becomes warmer 6

7. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Cooling Try this- Blow air onto your hand from your wide-open mouth…now pucker your lips and blow the air 7

8. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Cooling-occurs when gas expands (it does work on its surroundings) The expansion of the universe is cooling the universe 8

9. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Cooling-occurs when gas expands (it does work on its surroundings) Occurs high in the atmosphere- as air pockets flows up, air pressure decreases, which results in decreased temperature. This can occur in a tornado/thunderstorm. For every km the air rises, temp decreases 10 ºC 9

10. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Is it a good idea to wear a t-shirt if you are going up in a hot air balloon? 10

11. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Key Concept The temperature of a gas (air) may be changed by 1)adding or subtracting heat and/or 2)changing the pressure of the gas (air) 11

12. General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Adiabatic Cooling-occurs when gas expands (it does work on its surroundings) The key concept then is that when a gas expands it gives up its energy (or loses its energy) and becomes cooler 12