The Behavior of Gases

1. The Behavior of Gases Part 1

2. The Properties of Gases • Kinetic energy – • The energy due to motion • What does temperature measure? • The average kinetic energy of the particles within a sample of matter. In a gas, the temperature (in Kelvin) is a way of indicating how fast the particles are moving.

3. Kinetic Theory Revisited • Assumption #1: Physical Properties of Gas Particles • Hard, spherical particles • Individual volumes are insignificant • Lots of empty space between the particles (this is why gases are so compressible)

4. Kinetic Theory Revisited • Assumption #2: Intermolecular forces • Gas particles are not attracted to each other – no intermolecular forces • Gases expand to the shape and volume of their containers

5. Kinetic Theory Revisited • Assumption #3: Particle movement • Random walks • Perfectly elastic collisions, which means there is no average kinetic energy loss over time

6. Variable Describing Gases

7. Variable Describing Gases

8. Variable Describing Gases

9. Variable Describing Gases

10. Variable Describing Gases

11. The Gas Laws • Boyle’s Law: • For a fixed mass of gas at constant temperature, the volume of the gas varies inversely with pressure

12. The Gas Laws V1 • Example: • The pressure on 2.50 L of anesthetic gas changes from 105 kPa to 40.5 kPa. What will be the new volume if temperature remains constant? P1 P2

13. The Gas Laws

14. The Gas Laws • Charles’s Law: • The volume of a fixed mass of gas is directly proportional to its Kelvin temperature if the pressure is kept constant.

15. The Gas Laws V1 T1 = -50+273 = 223K • Example: • Exactly 5.00 L of air at -50oC is warmed to 100oC. What is the new volume if the pressure remains constant? T2 = 100+273 = 373K

16. The Gas Laws

17. The Gas Laws • Gay-Lussac’s Law: • The pressure and Kelvin temperature of a fixed mass of a gas are directly proportional at constant volume.

18. The Gas Laws P1 T1 = 27+273 = 300K • Example: • The pressure of an automobile tire is 198 kPa at 27oC. At the end of a trip on a hot sunny day , the pressure has risen to 225 kPa. Assuming the volume is constant, what is the new temperature? P2

19. The Gas Laws

20. The Gas Laws • Combined Gas Law: • A relationship describing the behavior of gases that combines Boyle’s law, Charles’s Law, and Gay-Lussac’s law.

21. The Gas Laws • Example: • A gas at 155 kPa and 25oC occupies a container with initial volume of 1.00 L. By changing the volume the pressure of the gas increases to 605 kPa as the temperature increases to 125oC. What is the new volume?

22. The Gas Laws • Example: • A gas at 155 kPa and 25oC occupies a container with initial volume of 1.00 L. By changing the volume the pressure of the gas increases to 605 kPa as the temperature increases to 125oC. What is the new volume? V1 = 1.00 L T1 = 25oC +273 = 298 K P1 = 155 kPa

23. The Gas Laws • Example: • A gas at 155 kPa and 25oC occupies a container with initial volume of 1.00 L. By changing the volume the pressure of the gas increases to 605 kPa as the temperature increases to 125oC. What is the new volume? V1 = 1.00 L V2 = ? T1 = 298 K T2 = 398 K P1 = 155 kPa P2 = 605 kPa

24. The Gas Laws