1. WE’RE IN THE HOME STRETCH! FINAL EXAM ONE WEEK FROM TODAY @ 8AM MAKE UP LAB OWL ASSIGNMENT WILL BE POSTED WED., COMPLETE BY SATURDAY Chapter 10: Gases (Mon. & Wed.) Chapter 11: Intermolecular Forces and the Liquid State (Fri.) December 7, 2009

2. Gases Why gases? What is a gas?  State of matter where distance between particles is much bigger than the particles

3. Properties of Gases PropertyCommon UnitOther UnitsSymbol Massgrams (g)mg, kg- Amountmoles (mol)nonen Volumeliters (L)mLV Pressureatmosphere (atm)bar, mmHg, psi, kPaP TemperatureKelvin (K)ºC, ºFT

4. Properties of Gases: What is pressure? Common Units of Gas Pressure 1 atm =1.013 bar 101.3 kPa (kilopascal) 760 torr 760 mmHg (mm mercury) 14.7 psi (pounds per sq. inch)

5. Kinetic Molecular Theory (Sec. 10.6) Molecules in a gas are always moving quickly and randomly Average kinetic energy is determined by temperature All gases at the same temperature have the same average kinetic energy, regardless of mass Gas molecules collide with each other and the walls of their container without losing energy (“elastic” collisions)

6. Kinetic Energy of Gases Kinetic energy of a single molecule Average kinetic energy for a collection of molecules:

7. How fast do molecules really move? O 2 gas at room temperature (25ºC = 298K)  Root-mean-square (rms) speed

8. Boltzmann Distribution Gas molecules move with a range of speeds

9. Boltzmann Distribution

10. Boltzmann Distribution & Molar Mass

11. Boltzmann Distribution and Temperature

12. Boltzmann Distribution Gas molecules move with a range of speeds On average, gas molecules move faster at higher temperatures Heavier gases move more slowly on average than lighter gases at the same temperature  Don’t confuse average kinetic energy with speed!

13. Which moves faster? 1. O 2 at 300 K 2. He at 300 K 3. same

14. Which moves faster? 1. O 2 at 250 K 2. O 2 at 300 K 3. same

15. Which has greater kinetic energy? 1. O 2 at 300 K 2. He at 300 K 3. same

16. All the O 2 molecules at 300 K move faster than all the molecules of O 2 at 200 K. 1. true 2. false