Review Kinetic Vs.
Potential Energy
Kinetic Molecular Theory
 Explains the behavior of gases
 Real gases– do not follow all the assumptions of this
theory.
 Theoretical, applies to an ideal gas
 Gas following all the assumptions of the theory.
Kinetic Molecular Theory
1) Gases are made up of TONS of particles, constantly
moving, and spread out.
1) Gas particles drive straight until they hit/collide with
something (ex. Wall, particles).
1) Small particles, HUGE space for them to roam! Gas volume
mainly empty space
Kinetic Molecular Theory
(cont.)
4) No force of attraction! –gas particles randomly move around
5) When gas particles collide with each other or a container wall,
no kinetic energy is lost when they collide.
6) Temperature determines average kinetic energy of gas particles.
-not all gas particles are moving at the same kinetic energy
Properties of Gases
 1) Expandable




No shape
No defined volume
Fills whatever container is available to it.
Move quickly and no attraction
 2) Fluid
 Gases move similar to liquids
 No attraction to worry about
 3) Low Density
 Least dense state of matter for most substances
 Due to distance between particles
Properties of Gases (cont.)
 4) Diffusion
 Gas particles mix with each other and disperse
 “Spontaneous mixing of gas particles from 2 substances due to random
motion” (ex. Perfume)
 5) Effusion
 Describes gas movement through a small opening. (ex. Tire puncture)
 Related to how fast gas particles can move.
 6) Compressibility
 Gas particles are able to be packed close together.
 Decreased volume

Pressure
 “force per unit area on a surface”
 Gas particles colliding against container and creating force

Force a gas exerts on its surroundings
 Unit = Newton (N)
 Amount of pressure dependent on Volume, Temperature, and
particle/molecule number.
 Ex. Atmospheric pressure
How do we measure
pressure?
 Barometer– atmospheric pressure
 Evangelista Torricelli (1600s)
 Mercury falls to 760 mm
 Air pressure holds 760 mm mercury column.
Vacuum
1 atm
Pressure
Barometer
760
mm
Hg
 The pressure of the
atmosphere at sea level will
hold a column of mercury
760 mm Hg.
 1 atm = 760 mm Hg
Pressure Units
 Common: mmHg (millimeters of Hg)
 Measurements done in “atmosphere units”
 1 atmosphere of pressure (atm) = (sea level, 0° C)




760 mmHg
760 torr
1.01325 x 105 Pa
101.325 kPa
Example 1:
 1.75 atm of pressure to mmHg
Example 2:
 570 torr of pressure to atmospheres.
 kPa?
Pressure Conversion
Practice
1. The tire pressure for one tire on my car reads 0.9813
atm. Convert this pressure to mmHg.
2. 200 torr ---------------- kPa
3. The atmosphere supports a column of mercury at 670
mm in height. What is the atmospheric pressure in atm?
4. 15 Pa ------------------ atm
5. A weather report gives a current atmospheric pressure
reading of 745.8 mmHg. Express this reading in
kilopascals.
Homework
 Post-Lab Questions
 Study for Kinetics Quiz on Tuesday