1. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 1 Chapter 11 Gases 11.1 Properties of Gases 11.2 Gas Pressure

2. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 2 Kinetic Molecular Theory of Gases Gases consist of small particles that move rapidly in straight paths have no attractive 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 Kelvin temperature

3. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 3 Atmospheric Pressure The atmospheric pressure is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth is about 1 atmosphere or a little less at sea level

4. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 4 Properties of Gases Gases are described in terms of four properties: pressure(P), volume(V), temperature(T), and amount(n).

5. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 5 Units of Pressure Gas pressure is described as a force acting on a specific area Pressure (P) = force area

6. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 6 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. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 7 A. What is 475 mmHg expressed in atm? 475 mmHg x 1 atm = 0.625 atm (2) 760 mmHg B. The pressure of a tire is measured as 2.00 atm. What is this pressure in mmHg? 2.00 atm x 760 mmHg = 1520 mmHg (2) 1 atm Solution

8. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 8 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

9. Basic Chemistry Copyright © 2011 Pearson Education, Inc. Units of Pressure 9

10. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 10 Altitude and Atmospheric Pressure Atmospheric pressure depends on the altitude and the weather is lower at high altitudes where the density of air is less is higher on a rainy day than on a sunny day

11. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 11 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 2) H 2 O is heavier 3) air is more dense than H 2 O Learning Check

12. Basic Chemistry Copyright © 2011 Pearson Education, Inc. 12 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. Solution