1. Gas Laws
Properties of Gases
Gas Pressure

2. Some workers cleaned the outside of this tanker
car with very hot water one afternoon. When they
came back in the morning, it looked like this!
What do you think happened to this tanker car?

3. Gases
What gases are important for each of the following: O2, CO2 and/or He?
A B C D.

4. Gases
What gases are important for each of the following: O2, CO2 and/or He?
A. CO B. O2/CO C. O2 D. He

5. Some Gases in Our Lives Air: oxygen O2 nitrogen N2 ozone O3
carbon dioxide CO2 water H2O
Noble gases:
helium He neon Ne krypton Kr
Other gases:
fluorine F2 chlorine Cl2 ammonia NH3
methane CH4 carbon monoxide CO
nitrogen dioxide NO2 sulfur dioxide SO2

6. The Nature of Gases Gases are compressible Gases have low densities
Why can you put more air in a tire, but
can’t add more water to a glass full of water?
Gases have low densities
Density of a solid or liquid = g/mL
Density of a gas = g/L

7. Nature of Gases 1. Why does a balloon become spherical
when filled with air?
2. Suppose we filled this room halfway with water.
Where would pressure be exerted?

8. Nature of Gases Gases fill a container completely and uniformly
Gases exert a uniform pressure
on all inner surfaces of their containers

9. Kinetic Theory of Gases
The particles in gases
Are very far apart
Move very fast in straight lines until they collide
Have no attraction (or repulsion)
Move faster at higher temperatures

10. Barometers

11. Learning Check 1) greater than 2) less than 3) the same as
If a barometer reads 760 mm Hg, the downward
pressure of the Hg in a barometer will be_____ the weight of 1 atmosphere.
1) greater than 2) less than 3) the same as

12. Solution If a barometer reads 760 mm Hg, the downward
pressure of the Hg in a barometer will be the same as the weight of 1 atmosphere.

13. Unit of Pressure One atmosphere (1 atm) standard for pressure
Is the average pressure of atmosphere at sea level
P = Force
Area
1.00 atm = 760 mm Hg = 760 torr

14. Learning Check 1) The weight of the atmosphere pushes it
When you drink through a straw you reduce the pressure in the straw. Why does the liquid go up the straw?
1) The weight of the atmosphere pushes it
2) The liquid is at a lower level than the straw
3) There is empty space in the straw
4) The pressure in your mouth is lower than the atm
Could you drink a soda this way on the moon?
1) yes ) no ) maybe Why or why not?

15. Solution 1) The weight of the atmosphere pushes it
When you drink through a straw you reduce the pressure in the straw. Why does the liquid go up the straw?
1) The weight of the atmosphere pushes it
3) There is empty space in the straw
4) The pressure in your mouth is lower than the atm
Could you drink a soda this way on the moon?
2) no
Why or why not? Low atmospheric pressure

16. Types of Pressure Units
Pressure Used in
760 mm Hg or 760 torr Chemistry
14.7 lb/in.2 (psi) U.S. pressure gauges
101,325 Pa (Pascal) SI Unit - Weather in all countries except U.S.
1.013 bars Physics and astronomy

17. Learning Check A. What is 475 mm Hg expressed in atm?
1) 475 atm ) atm 3) x 105 atm
B. The pressure of a tire is measured as 29.4 psi.
What is this pressure in mm Hg?
1) mm Hg
2) x 103 mmHg
3) 2.23 x 104 mm Hg
760 mm Hg = 1 atm 760 mm Hg = 14.7 psi

18. Solution A. What is 475 mm Hg expressed in atm?
475 mm Hg x atm = atm (B)
760 mm Hg
B. The pressure of a tire is measured as 29.4 psi.
What is this pressure in mm Hg?
29.4 psi x 760 mmHg = 1.52 x 103 mmHg
14.7 psi (B)