1. Particle Theory of Matter

3. Are able to move independently
Random motion
Move is straight lines until course is altered by collisions with other particles
Motion is fast
Liquids flow because they are influences by gravity
Gas particles move so fast that gravity does not affect them as much
Compressible
Motion in all directions until all available empty space is filled (expand)

5. Kinetic Molecular Theory
Theory developed to explain gas behavior.
Theory of moving molecules.

6. Assumptions:
Gases consist of a large number of molecules in constant random motion.
Volume of individual molecules negligible compared to volume of container.
Intermolecular forces (forces between gas molecules) negligible.
Energy can be transferred between molecules, but total kinetic energy is constant at constant temperature.
Average kinetic energy of molecules is proportional to temperature.

7. Kinetic molecular theory gives us an understanding of pressure and temperature on the molecular level.
Gas molecules have an average kinetic energy.
Each molecule has a different energy.

8. When particles are heated:
Particles move faster and have more collisions
Higher kinetic energy helps overcome attractive forces
Particles need more space, making the object expand

9. Pressure of a gas results from the number of collisions per unit time on the walls of container
Magnitude of pressure given by how often and how hard the molecules strike.

10. There is a spread of individual energies of gas molecules in any sample of gas.
As the temperature increases, the average kinetic energy of the gas molecules increases.

11. Pressure Pressure is the force acting on an object per unit area:
Gravity exerts a force on the earth’s atmosphere
Atmospheric pressure is the force per unit area exerted against a surface by the weight of the air above that surface.
A column of air 1 m2 in cross section exerts a force of 105 N.
The pressure of a 1 m2 column of air is 100 kPa.

13. Barometer

14. A Torricellian Barometer
At sea level, the average atmospheric pressure supports a column of mercury 760 mm high in a simple mercury barometer at 0oC
This average pressure is called one atmosphere.
A Torricellian Barometer

15. The height changes as atmospheric pressure changes.
Atmosphere Pressure and the Barometer
The height of the mercury column is a measure of the atmosphere’s pressure.
The height changes as atmospheric pressure changes.

17. Pressure and the Manometer
A manometer consists of a bulb of gas attached to a U-tube containing Hg
The pressures of gases not open to the atmosphere are measured in manometers.
The height of the mercury is in millimeters (mmHg)
If Pgas < Patm then Pgas + Ph = Patm.
If Pgas > Patm then Pgas = Patm + Ph.

18. Units of Pressure atmospheres (symbol = atm)
millimeters of mercury (symbol = mm Hg). This unit is also called a torr.
Pascals (symbol = Pa). A Pa is N/m2. More commonly used is kiloPascals (symbol = kPa). This is the SI unit for pressure.

19. Conversion Between Units
1 atm = mm Hg = kPa = Pa

20. Example #1 - Convert 0.875 atm to mmHg
1 atm = mmHg
0.875 atm ?
? = 665 mmHg
Example #2 - Convert mmHg to atm.
? mmHg
? = atm

21. Example #3 - Convert 0.955 atm to kPa
1 atm = kPa
0.955 atm ?
? = 96.8 kPa
Example #4 - Convert kPa to atm
1 atm = kPa
? kPa
? = atm

22. Example #5 - Convert 740.0 mmHg to kPa
760 mmHg = kPa
740 mmHg ?
? = 98.6 (99) kPa
Example #6 - Convert kPa to mmHg
? kPa
? = mmHg

23. Convert the following pressures:
658.2 mm Hg to kPa
1.85 atm to torr
337.3 kPa to atm
6.6 x 10-2 torr to atm
147.2 kPa to torr

24. Convert the following pressures:
658.2 mm Hg to kPa kPa
1.85 atm to torr x 103 torr
337.3 kPa to atm atm
6.6 x 10-2 torr to atm 8.7 x 10-5 atm
147.2 kPa to torr torr

25. The mercury in a manometer is 46 mm higher on the open end than on the gas bulb end. If atmospheric pressure is kPa, what is the pressure of the gas in the bulb?

26. On a certain day the barometer in a laboratory indicates that the atmospheric pressure is torr. A sample of gas is placed in a vessel attached to an open-end mercury manometer. A meter stick is used to measure the height of the mercury above the bottom of the manometer. The level of mercury in the open end arm of the manometer has a measured height of mm. In the arm that is in contact with the gas has a height of mm. What is the pressure of the gas (a) in atm and (b) in kPa?