2. TEKS 9C: Describe the postulates of kinetic molecular theory. 1 Gases Properties of Gases Gas Pressure Copyright © 2009 by Pearson Education, Inc.

3. TEKS 9C: Describe the postulates of kinetic molecular theory. 2 Kinetic Theory of Gases A gas consists of small particles that move rapidly in straight lines. have essentially no attractive (or repulsive) forces. are very far apart. have very small volumes compared to the volume of the container they occupy. have kinetic energies that increase with an increase in temperature. Copyright © 2009 by Pearson Education, Inc.

4. TEKS 9C: Describe the postulates of kinetic molecular theory. 3 Properties That Describe a Gas Gases are described in terms of four properties: pressure (P), volume (V), temperature (T), and amount (n). Copyright © 2009 by Pearson Education, Inc.

5. TEKS 9C: Describe the postulates of kinetic molecular theory. 4 Gas pressure is a force acting on a specific area. Pressure (P) = force area has units of atm, mmHg, torr, lb/in. 2, and kilopascals(kPa). 1 atm = 760 mm Hg (exact) 1 atm = 760 torr 1 atm = 14.7 lb/in. 2 1 atm = 101 325 Pa 1 atm = 101.325 kPa Gas Pressure

6. TEKS 9C: Describe the postulates of kinetic molecular theory. 5 A. What is 475 mmHg expressed in atm? 1) 475 atm 2) 0.625 atm 3) 3.61 x 10 5 atm B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg? 1) 2.00 mmHg 2) 1520 mmHg 3)22 300 mmHg Learning Check

7. TEKS 9C: Describe the postulates of kinetic molecular theory. 6 Solution A. What is 475 mmHg expressed in atm? 2) 0.625 atm 475 mmHg x 1 atm = 0.625 atm 760 mmHg B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg? 2) 1520 mmHg 2.00 atm x 760 mmHg = 1520 mmHg 1 atm

8. TEKS 9C: Describe the postulates of kinetic molecular theory. 7 Atmospheric Pressure Atmospheric pressure is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth. Copyright © 2009 by Pearson Education, Inc.

9. TEKS 9C: Describe the postulates of kinetic molecular theory. 8 Altitude and Atmospheric Pressure Atmospheric pressure is about 1 atmosphere at sea level. depends on the altitude and the weather. is lower at higher altitudes, where the density of air is less. is higher on a rainy day than on a sunny day. Copyright © 2009 by Pearson Education, Inc.

10. TEKS 9C: Describe the postulates of kinetic molecular theory. 9 Barometer A barometer measures the pressure exerted by the gases in the atmosphere. indicates atmospheric pressure as the height in mm of the mercury column. Copyright © 2009 by Pearson Education, Inc.

11. TEKS 9C: Describe the postulates of kinetic molecular theory. 10 A. The downward pressure of the Hg in a barometer is _____ than (as) the pressure of the atmosphere. 1) greater 2) less 3) the same B. A water barometer is 13.6 times taller than a Hg barometer (D Hg = 13.6 g/mL) because 1) H 2 O is less dense than mercury. 2) H 2 O is heavier than mercury. 3) air is more dense than H 2 O. Learning Check

12. TEKS 9C: Describe the postulates of kinetic molecular theory. 11 A.The downward pressure of the Hg in a barometer is 3) the same (as) the pressure of the atmosphere. B. A water barometer is 13.6 times taller than a Hg barometer (D Hg = 13.6 g/mL) because 1) H 2 O is less dense than mercury. Solution

13. TEKS 9C: Describe the postulates of kinetic molecular theory. Temperature Conversion Equations 2 equations to use: K = o C + 273 o C = K – 273

14. TEKS 9C: Describe the postulates of kinetic molecular theory. Practice Problem #1 240 o C = ____K K = o C + 273 K = 240 + 273 K = 513

15. TEKS 9C: Describe the postulates of kinetic molecular theory. Practice Problem #2 350K = ____ o C o C = K – 273  o C = 350 – 273  o C = 77

16. TEKS 9C: Describe the postulates of kinetic molecular theory. Practice Problem #3 510K = ____ o C o C = K – 273  o C = 510 – 273  o C = 237

17. TEKS 9C: Describe the postulates of kinetic molecular theory. Practice Problem #4 20 o C = ____K K = o C + 273 K = 20 + 273 K = 293

18. TEKS 9C: Describe the postulates of kinetic molecular theory. The End