Properties of Gases

1. Properties of Gases • A soccer ball properly inflated will rebound faster and travel farther than an under-inflated ball. If the pressure is too high, the ball may burst when it is kicked. We will study the variables that affect the pressure of a gas.

3. Compressibility • Compressibility • Why are gases easier to compress than solids or liquids are?

4. Compressibility • Compressibility is a measure of how much the volume of matter decreases under pressure. When a person collides with an inflated airbag, the compression of the gas absorbs the energy of the impact.

5. Compressibility • Gases are easily compressed because of the space between the particles in a gas. • The distance between particles in a gas is much greater than the distance between particles in a liquid or solid. • Under pressure, the particles in a gas are forced closer together.

6. Compressibility • At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.

7. Factors Affecting Gas Pressure • Factors Affecting Gas Pressure • What are the three factors that affect gas pressure? • Amount of Gas • Volume • Temperature

8. Factors Affecting Gas Pressure • Four variables are generally used to describe a gas. The variables and their common units are • pressure (P) in kilopascals • volume (V) in liters • temperature (T) in kelvins • the number of moles (n).

9. Factors Affecting Gas Pressure • Amount of Gas • You can use kinetic theory to predict and explain how gases will respond to a change of conditions. If you inflate an air raft, for example, the pressure inside the raft will increase.

10. Heat • Energy transferred due to differences in temperature • Temperature • Measure of the average kinetic energy of particles composing a material • Pressure • Force per unit area • Volume • The amount of space a material occupies

11. Factors Affecting Gas Pressure • Collisions of particles with the inside walls of the raft result in the pressure that is exerted by the enclosed gas. • If you increase the number of particles it will increase the number of collisions, which is why the gas pressure increases.

12. Factors Affecting Gas Pressure • If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst.

13. Factors Affecting Gas Pressure • Aerosol Spray Paint

14. Factors Affecting Gas Pressure • Volume • You can raise the pressure exerted by a contained gas by reducing its volume. The more a gas is compressed, the greater is the pressure that the gas exerts inside the container.

15. Factors Affecting Gas Pressure • When the volume of the container is halved, the pressure the gas exerts is doubled.

16. Factors Affecting Gas Pressure • Temperature • An increase in the temperature of an enclosed gas causes an increase in its pressure. • As a gas is heated, the average kinetic energy of the particles in the gas increases. Faster-moving particles strike the walls of their container with more energy.

17. Factors Affecting Gas Pressure • When the Kelvin temperature of the enclosed gas doubles, the pressure of the enclosed gas doubles.

18. 14.1 Section Quiz. • 14.1.

19. 14.1 Section Quiz. • 1. Compared to liquids and solids, gases are easily compressed because the particles in a gas • attract each other. • are spaced relatively far apart. • are very small. • repel each other.

20. 14.1 Section Quiz. • 2. Gas pressure is affected by • temperature, volume, and the amount of the gas. • temperature, volume, and the molar mass of the gas. • phase diagram, volume, and the size of the container. • temperature, phase diagram, and the mass of the gas container.

21. 14.1 Section Quiz. • 3. For gases, the SI units for volume (V), pressure (P), and temperature (T) are, respectively, • liters, kilopascals, and °C. • liters, kilopascals, and kelvins. • cm3, kilopascals, and kelvins. • liters, atmospheres, and °C.

22. The Gas Laws • This hot air balloon was designed to carry a passenger around the world. You will study some laws that will allow you to predict gas behavior under specific conditions, such as in a hot air balloon.

23. Boyle’s Law: Pressure and Volume • Boyle’s Law: Pressure and Volume • How are the pressure, volume, and temperature of a gas related?

24. Boyle’s Law: Pressure and Volume • If the temperature is constant, as the pressure of a gas increases, the volume decreases.

25. Boyle’s Law: Pressure and Volume • Boyle’s law states that for a given mass of gas at constant temperature, the volume of the gas varies inversely with pressure.

26. Boyle’s Law: Pressure and Volume

27. Boyle’s Law: Pressure and Volume • Simulation 15 • Examine the relationship between gas, volume and pressure.

28. 14.1

29. 14.1

30. 14.1

31. 14.1

32. for Sample Problem 14.1 • Problem Solving 14.8 • Solve Problem 8 with the help of an interactive guided tutorial.