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LecturePLUS Timberlake1 Gases Properties of Gases Gas Pressure.

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Presentation on theme: "LecturePLUS Timberlake1 Gases Properties of Gases Gas Pressure."— Presentation transcript:

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2 LecturePLUS Timberlake1 Gases Properties of Gases Gas Pressure

3 LecturePLUS Timberlake2 Gases What gases are important for each of the following: O 2, CO 2 and/or He? A. B. C. D.

4 LecturePLUS Timberlake3 Gases What gases are important for each of the following: O 2, CO 2 and/or He? A. CO 2 B. O 2 /CO 2 C. O 2 D. He

5 LecturePLUS Timberlake4 Some Gases in Our Lives Air: oxygen O 2 nitrogen N 2 ozone O 3 argon Ar carbon dioxide CO 2 water H 2 O Noble gases: helium He neon Ne krypton Kr xenon Xe Other gases: fluorine F 2 chlorine Cl 2 ammonia NH 3 methane CH 4 carbon monoxide CO nitrogen dioxide NO 2 sulfur dioxide SO 2

6 LecturePLUS Timberlake5 The Nature of Gases Gases are compressible Why can you put more air in a tire, but cant add more water to a glass full of water? Gases have low densities Dsolid or liquid = 2 g/mL Dgas 2 g/L

7 LecturePLUS Timberlake6 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?

8 LecturePLUS Timberlake7 Nature of Gases Gases fill a container completely and uniformly Gases exert a uniform pressure on all inner surfaces of their containers

9 LecturePLUS Timberlake8 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 LecturePLUS Timberlake9 Barometers 760 mmHg atm pressure

11 LecturePLUS Timberlake10 Learning Check G1 A.The downward pressure of the Hg in a barometer is _____ than (as) the weight of the atmosphere. 1) greater2) less 3) the same B.A water barometer has to be 13.6 times taller than Hg barometer (D Hg = 13.6 g/mL) because 1) H 2 O is less dense 2) Hg is heavier 3) air is more dense than H 2 O

12 LecturePLUS Timberlake11 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 (D Hg = 13.6 g/mL) because 1) H 2 O is less dense

13 LecturePLUS Timberlake12 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

14 LecturePLUS Timberlake13 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 2) no 3) maybe Why or why not?

15 LecturePLUS Timberlake14 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

16 LecturePLUS Timberlake15 Types of Pressure Units PressureUsed in 760 mm Hg or 760 torr or 1 atm Chemistry 14.7 lb/in. 2 U.S. pressure gauges 29.9 in. HgU.S. weather reports kPa (kilopascals)Weather in all countries except U.S barsPhysics and astronomy

17 LecturePLUS Timberlake16 Learning Check G3 A. What is 475 mm Hg expressed in atm? 1) 475 atm 2) atm 3) 3.61 x 10 5 atm B. The pressure of a tire is measured as 29.4 psi. What is this pressure in mm Hg? 1) 2.00 mm Hg 2) 1520 mm Hg 3)22,300 mm Hg

18 LecturePLUS Timberlake17 Solution G3 A. What is 475 mm Hg expressed in atm? 485 mm Hg x 1 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 10 3 mmHg 14.7 psi 1.00 atm (B)


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