The Behavior of Gases

1. The Behavior of Gases 14.1 Properties of Gases 14.2 The Gas Laws 14.3 Ideal Gases 14.4 Gases: Mixtures and Movements Created by C. Ippolito May 2007

2. Properties of Gases Objectives: Explain why gases are easier to compress than solids or liquids are. Describe the three factors that affect gas pressure. Created by C. Ippolito May 2007

3. Compressibility • a measure of how much the volume of matter decreases under pressure • gases compress more easily because of the space between the particles • Factors Affecting Gas Pressure • amount of gas • volume • temperature Created by C. Ippolito May 2007

4. Amount of Gas and Gas Pressure • Amount of Gas – more particles in a fixed area more collisions more pressure Created by C. Ippolito May 2007

5. Volume and Gas Pressure • Volume – more a gas is compressed the greater the pressure exerted on the container Created by C. Ippolito May 2007

6. Temperature and Gas Pressure • Temperature – heating the gas increases kinetic energy, increasing collisions, increasing pressure Created by C. Ippolito May 2007

7. The Gas Laws Objectives: Describe the relationships among temperature, pressure, and volume of a gas Use the combined gas law to solve problems. Created by C. Ippolito May 2007

8. Boyle’s Law • If temperature is constant, the volume of a given mass of gas varies inversely with pressure • when pressure  then volume  • when pressure  then volume  Created by C. Ippolito May 2007

9. Using Boyle’s Law Created by C. Ippolito May 2007

10. Charles’s Law • As the temperature (in Kelvin) of an enclosed gas increases, the volume increases, if the pressure is constant. Created by C. Ippolito May 2007

11. Using Charles’s Law Created by C. Ippolito May 2007

12. Gay-Lussac’s Law • As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant Created by C. Ippolito May 2007

13. Using Gay-Lussac’s Law Created by C. Ippolito May 2007

14. The Combined Gas Law • allows you to do calculations for situations in which only the amount of gas is constant. • Combines Boyle’s, Charles’s, and Gay-Lussac’s laws Created by C. Ippolito May 2007

15. Using the Combined Gas Law Created by C. Ippolito May 2007

16. Ideal Gases Objectives: Compute the value of an unknown using the ideal gas law Compare and contrast real and ideal gases. Created by C. Ippolito May 2007

17. Ideal Gas Law • includes all four variables (pressure, volume, temperature, moles) and allows you to calculate the number of moles in a gas law problem • n = # of moles • R = ideal gas constant = 8.31 (L•kPa)/(K•mol) Created by C. Ippolito May 2007

18. Using the Ideal Gas Law Created by C. Ippolito May 2007

19. Ideal Gas • follows the gas laws at all conditions of pressure and temperature • real gases differ most from ideal gases at low temperatures and high pressures • real gases are most like ideal gases at high temperatures and low pressures Created by C. Ippolito May 2007

20. Gases: Mixtures and Movements Objectives: Relate the total pressure of a mixture of gases to the partial pressures of the component gases Explain how the molar mass of a gas affects the rate at which the gas diffuses and effuses. Created by C. Ippolito May 2007

21. Dalton’s Law • In a mixture of gases, the total pressure is the sum of the partial pressures of the gases Created by C. Ippolito May 2007

22. Graham’s Law • Diffusion – molecules move from area of high concentration to an area of low concentration • Effusion – gases can escape from container through a small hole • Gases of lower molar masses diffuse and effuse faster than gases of higher molar mass Created by C. Ippolito May 2007