1. Chapter 11
Gas Laws

2. Elements that exist as gases at 250C and 1 atmosphere

3. Physical Characteristics of Gases
Gases assume the volume and shape of their containers.
Gases are the most compressible state of matter.
Gases will mix evenly and completely when confined to the same container.
Gases have much lower densities than liquids and solids.

4. The weight of the air (gas molecules) pushing down on Earth
Force
Area
Barometer
What is Pressure?
Pressure =
The weight of the air (gas molecules) pushing down on Earth
Pressure is Measured in Units of:
Pascals (Pa), millimeters of mercury, (mmHg), torr (torr), atmosphere (atm), and pounds of square inch (psi)

5. STP- Standard Temperature and Pressure
To compare volumes of gases, one must know temperature and pressure at which the volumes are measured.
Scientists have agreed upon standards conditions of exactly 1 atm pressure and 0 degrees celsius (273K).

6. 1 atmosphere of pressure = 760 mmHg
Under STP:
1 atmosphere of pressure = 760 mmHg
1atm = 760 torr
1 atm = kPa
1atm = 14.7psi

7. The average atmospheric pressure at sea level is 1 atm
The average atmospheric pressure at sea level is 1 atm. Basically the weight of air at sea level is equal to 1 atm. What happens to atm pressure as you move further away from sea level?
10 miles
0.2 atm
4 miles
0.5 atm
Sea level
1 atm

8. A Torricellian barometer (sometimes called a mercury barometer) is an inverted (upside-down) glass tube standing in a bath of mercury.
Air pressure pushes down on the surface of the mercury, making some rise up the tube. The greater the air pressure, the higher the mercury rises

9. Convert Units of Pressure:
Example #1:
Express atm in units of mmHg and kPa
0.830 atm x mmHg = 631 mmHg
1 atm
0.830 atm x kPa = kPa
1 atm

10. Dalton’s Law of Partial Pressures
In a mixture of gases, the total pressure is calculated by adding the pressure of each individual gas in the mixture.
V and T are constant P1 P2
Ptotal = P1 + P2

11. Classwork
Page 367 #’s 1-6
*Appendix A8 is on page 859

12. KEY Pg. 367 #1-6 1. Force / Area 2. mmHg, torr, kPa, psi, atm
3. STP = 273K and 1 atm
4. a) kPa x 1 atm = atm
101.3kPa
b) 456 torr x atm = x 10-1 atm
760 torr
Ptotal = 785 mmHg, PH2O = 21.1 mmHg of 21.1 torr ( 1mmHg is equal to 1 torr)
Ptotal – PH2O = PN mmHg – 21.1 mmHg = 764 mmHg
6. The pressure that each gas exerts is independent of thepressues exerted by the other gases.