1. Gases

2. Copyright © Houghton Mifflin Company.All rights reserved. 12–2 A skydiver leaps into the earth's atmosphere, which is composed of a mixture of gases. Source: Brian Erler/Taxi/Getty Images

3. Steve Fossett flies his balloon Solo Spirit, over the east coast of Australia during his attempt to make the first solo balloon flight around the world. Source: AP Photo/Steve Holland

4. Copyright © Houghton Mifflin Company.All rights reserved. 12–4 Figure 12.1: The pressure exerted by the gases in the atmosphere can be demonstrated by boiling water in a can.

5. Figure 12.2: When a glass tube is filled with mercury and inverted in a dish of mercury at sea level, the mercury flows out of the tube until a column approximately 760 mm high remains.

6. Copyright © Houghton Mifflin Company.All rights reserved. 12–6 Figure 12.3: A device (called a manometer) for measuring the pressure of a gas in a container.

7. Checking the air pressure in a tire.

8. Copyright © Houghton Mifflin Company.All rights reserved. 12–8

9. Figure 12.4: A J-tube similar to the one used by Boyle.

10. Figure 12.5: A plot of P versus V from Boyle’s data in Table 12.1.

11. Copyright © Houghton Mifflin Company.All rights reserved. 12–11 Figure 12.6: Illustration of Boyle’s law.

12. Copyright © Houghton Mifflin Company.All rights reserved. 12–12 Neon signs in Hong Kong Source: Dave Jacobs/Stone/Getty Images

13. Figure 12.7: Plots of V (L) versus T (°C) for several gases.

14. Figure 12.8: Plots of V versus T as in Figure 12.7, except that here the Kelvin scale is used for temperature.

15. The air in a balloon expands when it is heated. This means that some of the air escapes from the balloon, lowering the air density inside and thus making the balloon buoyant. Source: John A. Rizzo/ PhotoDisc/Getty Images

16. Copyright © Houghton Mifflin Company.All rights reserved. 12–16 Researchers take samples from a steaming volcanic vent at Mount Baker in Washington. Source: USGA Photo by T. Casadevall

17. Copyright © Houghton Mifflin Company.All rights reserved. 12–17 Figure 12.9: The relationship between volume V and number of moles n. As the number of moles is increased from 1 to 2 (a to b), the volume doubles.

18. Popcorn popping.

19. Copyright © Houghton Mifflin Company.All rights reserved. 12–19 Figure 12.10: When two gases are present, the total pressure is the sum of the partial pressures of the gases.

20. Copyright © Houghton Mifflin Company.All rights reserved. 12–20 Figure 12.11: The total pressure of a mixture of gases depends on the number of moles of gas particles (atoms or molecules) present, not on the identities of the particles.

21. Copyright © Houghton Mifflin Company.All rights reserved. 12–21 Divers use a mixture of oxygen and helium in their breathing tanks when diving to depths greater than 150 feet. Source: Kurt Amsler/Vandystadt/Allsport/Getty Images

22. Copyright © Houghton Mifflin Company.All rights reserved. 12–22 Figure 12.12: The production of oxygen by thermal decomposition of KClO 3.

23. Copyright © Houghton Mifflin Company.All rights reserved. 12–23

24. Copyright © Houghton Mifflin Company.All rights reserved. 12–24

25. Copyright © Houghton Mifflin Company.All rights reserved. 12–25 Figure 12.13: (a) A gas confined in a cylinder with a movable piston. (b) The temperature of the gas is increased at constant pressure P ext.