1. Unit 7 - Gases Chapter 13 Gases - How do we characterize them? What makes them different than condensed phases? Pressure... Can you feel it now? How do you know it’s there? What is pressure? Units?

2. Pressure What causes pressure? Collisions of gas particles with the container walls Standard Pressure 101.3 kPa 760 mmHg 760 Torr (for Torricelli - inventor of barometer) 1 atm

3. Barometer http://en.wikipedia.org/wiki/Barometer

4. Kinetic Theory of Gases Postulates of KMT Gases consist of tiny particles So small that spaces between are large, so volume is ~ zero In constant random motion – collisions are perfectly elastic (no energy loss by collisions) No attractive forces between them KE ave is proportional to the Kelvin Temperature

6. Boyle’s Law Boyle conducted experiment’s at constant T P x V = constant, P and V are inversely related So if we know the initial conditions of a system, we can calculate new information P 1 x V 1 = P 2 x V 2

7. Charles’ Law Charles conducted experiment’s at constant P V / T = constant, T and V are directly related So if we know the initial conditions of a system, we can calculate new information V 1 / T 1 = V 2 / T 2 ; Temp must be in Kelvin

8. Boyle’s Law graphic

9. Charles’s Law graphic

10. Combined Gas Law Combine Boyle’s and Charles’ Laws P 1 x V 1 = P 2 x V 2 V 1 / T 1 = V 2 / T 2 Becomes P 1 x V 1 / T 1 = P 2 x V 2 / T 2 can vary multiple conditions....

12. Ideal Gas Problem Example What volume will 23 g of carbon dioxide occupy at 56 o C and 795 Torr?

13. Density and molar mass with ideal gas law What is density? Using ideal gas law what is similar? We can get moles/liter, n/V = P/RT Calculate that and use the molecular formula to get density What is the density of P 2 O 5 at 600 mmHg and 37 o C?

14. Temperature and KE

16. Dalton’s Law of Partial Pressures

17. Real vs Ideal Gases Gases are all REAL substances... We have a Kinetic Molecular Theory that makes postulates so that we can describe gases at “normal” pressures and temperatures. When does a gas fail to behave ideally? Low Temperatures (attractive forces begin to play a roll) Gases condense! High Pressure ( gases have volume, spaces between them become smaller) Review Assignment Page 418-423 #7abc, 19abc, 31abc, 42, 49abc, 68, 78-80, 82,87