1. Physical Characteristics of Gases
Chapter 10

2. I. Kinetic-Molecular Theory of Matter - the particles of matter are always moving
A. Ideal Gas – an imaginary gas that fits all the following assumptions
Gas particles are far apart
Collisions of gas particles are elastic (no kinetic energy lost)
Gas particles move rapidly
No attraction between particles
Energy of particles increases at higher temperatures

3. I. Kinetic-Molecular Theory of Matter
B. At the same temperature, all gas particles have the same amount of energy; this means that lighter particles are moving faster than heavier particles K.E. = mv2 K.E. = kinetic energy 2 v = velocity m = mass

4. I. Kinetic-Molecular Theory of Matter
Physical Properties of Gases
Expansion - gas particles spread out to fill any container
Fluidity
Gas particles can slide past one another
Gases and liquids are “fluids”
Low density
Compressibility
Diffusion

5. I. Kinetic-Molecular Theory of Matter
D. Real Gases 1. close to ideal gas at normal conditions 2. have volume and attraction between particles 3. deviation from ideal gas is greater when: a. particles are close together (low temperature and high pressure) b. gas is a compound rather than an element

6. Pressure – force per unit area
II. Pressure
Pressure – force per unit area
P = force (N) Newton
area
Gas pressure is a result of collisions of gas particles. The pressure depends on the number of gas particles, the temperature and the volume.
Instruments used to measure pressure
Barometer is used to measure atmospheric pressure
Manometer is used to measure the pressure of a gas in a container

7. II. Pressure
D. Units of Pressure 1. mm Hg or torr (1mm Hg = 1 torr) 2. atmospheres (atm) 3. Pascal (Pa) a. the SI unit of pressure (newton (N) is SI unit of force b. atmospheres (atm) c. 1kPa = 1000Pa

8. II. Pressure
E. Standard Pressure 760 mm Hg = 760 torr = 1atm = 101.3kPa F. Standard Temperature and Pressure (STP) 1 atm and 00 C

9. II. Pressure
G. Convert 745 torr to kilopascals H. Convert 245 kilopascals to atmosphere of pressure

10. III. Gas Laws Boyles’ Law
Reducing the volume by one-half doubles the pressure
The volume of a fixed mass of gas varies inversely with the pressure at constant temperature
P1V1 = P2V2
When a sample of gas is moved from a 2.50L container to a different container, the pressure changes from kPa to 40.5 kPa. Find the volume of the new container (temperature constant)

11. III. Gas Laws Boyles’ Law
Reducing the volume by one-half doubles the pressure
The volume of a fixed mass of gas varies inversely with the pressure at constant temperature
P1V1 = P2V2

12. III. Gas Laws
A. 4. When a sample of gas is moved from a 2.50L container to a different container, the pressure changes from kPa to 40.5 kPa. Find the volume of the new container (temperature constant)

13. III. Gas Laws
5. A balloon is filled with 30.0L of helium at 1.0 atm. Find the pressure at an altitude where the balloon has expanded to 120 L. (temperature constant)

14. III. Gas Laws
B. Charles’Law 1. If the Kelvin temperature is doubled, the volume will double 2. Kelvin Temperature a. absolute zero (0.0 Kelvin) is the temperature at which molecules stop moving b. K = degree Celsius c. the volume of a fixed mass of gas at constant pressure varies directly with Kelvin temperature

15. III. Gas Laws
B. Charles’Law 3. V1 = V2 Charles’ Law T1 T2 (T must be Kelvin) 4. A sample of gas occupies 7.4 L at 310 degrees Celsius. Find the volume at which the temperature is 25 degrees Celsius. (constant pressure)

16. III. Gas Laws
B. Charles’Law 5. A baloon has a volume of 5.000L. When heated to 63 degrees Celsius, it has a volume of 5.6L. Find the initial Celsius temperature. (constant pressure)

17. III. Gas Laws
C. Gay-Lussac’s Law 1. doubling the Kelvin temperature doubles the pressure 2. the pressure of a fixed mass of gas at constant volume varies directly with the Kelvin temperature 3. P1 = P2 T1 T2 4. A gas has a pressure of 50.0 torr at 267 degrees Celsius. Find the pressure at -73 degrees Celsius. (constant volume)

18. III. Gas Laws
D. Combined Gas Law 1. P1V1 = P2V2 T1 T2 2. a gas occupies cm3 at 27.0 degrees Celsius and atm. Find the Celsius temperature at 10.9 cm3 and 1.00 atm.

19. III. Gas Laws
E. Dalton’s Law of Partial Pressures – the total pressure of a mixture of gases is equal to the sum of the partial pressures of the gases in the mixture. 1. PT = P1 + P2 + … 2. Gases Collected by Displacement of Water a. Atmospheric pressure equals the pressure of the gas plus the pressure of the water vapor Patm = Pgas + PH2O

20. III. Gas Laws
E. 2. b. Table p.899 for vapor pressure of water c. Find the pressure of oxygen gas collected over water at 25 degrees Celsius if the barometer reading is 752 mm Hg