1. Chapter 11 The Nature of Gases & Measuring Gases Pages 361 - 368

2. Characteristics of Gases Gases have mass. Gases can be compressed easily. (Liquids and solids DO NOT have this property.) Gases fill their container completely.

3. Characteristics of Gases Different gases can move through each other rapidly. (Diffusion) Gases can escape through a tiny pinhole or pore. (Effusion)

4. Characteristics of Gases Gas pressure depends on temperature, and the number of particles. High temp = High pressure Low temp = Low pressure Gases exert pressure.

5. Kinetic Molecular Theory 1.A gas consists of very small particles, each of which has a mass. 2.The distances separating gas particles are relatively large. 3.Gas particles are in constant, rapid, random motion.

6. Collisions of gas particles Energy is conserved in an elastic collision! “perfectly elastic”

7. Kinetic Molecular Theory 4. The average kinetic energy of gas particles depends only on the temperature of the gas.

8. Kinetic Molecular Theory 5. Gas particles exert no force on one another. There are no attractive or repulsive forces between gas particles.

9. PressurePressure

10. PressurePressure Pressure is exerted by the force of the collisions of gas particles with the walls of the container. More Collisions = Higher Pressure Fewer Collisions = Lower Pressure

11. PressurePressure KEY UNITS AT SEA LEVEL 101.3 kPa (kilopascal) = 101,300 Pa = 1 atm (atmosphere) = 760 mm Hg = 14.7 psi (pounds per square inch)= 760 torr Named for Torricelli who came up with idea for barometer.

12. BarometerBarometer Measures atmospheric pressure Mercury Barometer Aneroid Barometer

13. ManometerManometer Measures enclosed gas pressure U-tube Manometer Bourdon-tube gauge

14. Standard Temperature & Pressure 0°C 273 K 1 atm101.325 kPa -OR- STP

15. Measuring Gases: Temperature ºF ºC K -45932212 -2730100 0273373 K = ºC + 273 Always use absolute temperature (Kelvin) when working with gases.

16. Practice Problems #1 The air pressure for a certain tire is 109 kPa. What is this pressure in atmospheres? Need to know: 101.3 kPa = 1 atm

17. Pressure Conversion 109 kPa 101.3 kPa 1 atm = 1.08 atm

18. Practice Problems #10 A soccer ball is attached to an open-ended manometer. The mercury level in the manometer is 10 mm higher on the side attached to the ball than on the side open to the atmosphere. Atmospheric pressure is 770 mm Hg. What is the gas pressure in the ball?

19. *Practice Problems #10 THINK! P gas = 770 mmHg - 10 mm Hg The mercury is higher on the side attached to the ball, so the ATMOSPHERIC PRESSURE must be higher than the pressure in the soccer ball. P gas = 760 mmHg

20. Measuring Gases AMOUNT:Expressed in MOLES. Do you remember molar conversions? MASS PARTICLES MOLES X MOLAR MASS  MOLAR MASS X 6.02 x 10 23  6.02 x 10 23

21. Measuring Gases VOLUME:Expressed in LITERS. MOLES LITERS  22.4L x 22.4L Could also be other units 1L = 1000 cm 3