1. LecturePLUS Timberlake
Chapter 7 Gases
Properties of Gases
Gas Pressure
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2. LecturePLUS Timberlake
Gases
What gases are important for each of the following: O2, CO2 and/or He?
A B C D.
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3. LecturePLUS Timberlake
Gases
What gases are important for each of the following: O2, CO2 and/or He?
A. CO B. O2/CO C. O2 D. He
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4. LecturePLUS Timberlake
Some Gases in Our Lives
Air:
oxygen O2 nitrogen N2 ozone O3
argon Ar carbon dioxide CO2 water H2O
Noble gases:
helium He neon Ne krypton Kr xenon Xe
Other gases:
fluorine F2 chlorine Cl2 ammonia NH3
methane CH4 carbon monoxide CO
nitrogen dioxide NO2 sulfur dioxide SO2
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5. LecturePLUS Timberlake
The Nature of Gases
Gases are compressible
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
Dsolid or liquid = 2 g/mL
Dgas 2 g/L
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6. LecturePLUS Timberlake
Nature of Gases
1. Why does a round balloon
become spherical when filled
with air?
2. Suppose we filled this room halfway with water. Where would pressure be exerted?
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7. LecturePLUS Timberlake
Nature of Gases
Gases fill a container completely and uniformly
Gases exert a uniform pressure on all inner surfaces of their containers
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8. 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
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9. LecturePLUS Timberlake
Barometers
760 mmHg
atm
pressure
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10. LecturePLUS Timberlake
Learning Check G1
A.The downward pressure of the Hg in a barometer is _____ than (as) the weight of the atmosphere.
1) greater 2) less 3) the same
B.A water barometer has to be 13.6 times taller than Hg barometer (DHg = 13.6 g/mL)
because
1) H2O is less dense 2) Hg is heavier
3) air is more dense than H2O
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11. LecturePLUS Timberlake
Solution G1
A.The downward pressure of the Hg in a barometer is 3) the same (as) the weight of the atmosphere.
B.A water barometer has to be 13.6 times taller than Hg barometer (DHg = 13.6 g/mL)
because
1) H2O is less dense
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12. LecturePLUS Timberlake
Unit of Pressure
One atmosphere (1 atm)
Is the average pressure of the atmosphere at sea level
Is the standard of pressure
P = Force
Area
1.00 atm = 760 mm Hg = 760 torr
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13. LecturePLUS Timberlake
Learning Check G2
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
3) there is empty space in the straw
Could you drink a soda this way on the moon?
1) yes ) no 3) maybe
Why or why not?
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14. LecturePLUS Timberlake
Solution G2
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
Could you drink a soda this way on the moon?
2) no
Why or why not? Low atmospheric pressure
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15. Types of Pressure Units
Pressure Used in
760 mm Hg or 760 torr Chemistry
14.7 lb/in.2 U.S. pressure gauges
29.9 in. Hg U.S. weather reports
101.3 kPa (kilopascals) Weather in all countries except U.S.
1.013 bars Physics and astronomy
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16. LecturePLUS Timberlake
Learning Check G3
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) mm Hg
3) 22,300 mm Hg
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17. LecturePLUS Timberlake
Solution G3
A. What is 475 mm Hg expressed in atm?
485 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 1.00 atm x 760 mmHg = 1.52 x 103 mmHg
14.7 psi atm (B)
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