Chapter 10: Physical Characteristics of Gases
Kinetic Molecular Theory of Gases P. 303- 304
Ideal Gas: imaginary, conforms to all assumptions
Kinetic Molecular Theory
1. Gases consist of large numbers of molecules in continuous random motion
2. The volume of gas molecules is negligible compared to total volume of gas
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Molecules (or atoms) are considered point masses with no diameter or volume
3. Attractive and repulsive forces between gas molecules are negligible. i.e.: molecules/ atoms have no
effect on each other
4. Molecular/ atomic collisions are perfectly elastic. *No energy is lost if a collision occurs*
5. The average kinetic energy = (1/2 mv2) of the molecules is proportional to absolute temperature in
Kelvin
Energy
Kinetic Energy= ½ mv2
Potential Energy= mgh (m = mass; g = gravity; h = height)
Law of Conservation of Energy: not created or destroyed, can change form
Matter
Matter: has mass and takes up space
Solid: definite shape and volume
Liquid: takes the shape of the container and has definite volume
Gas: no definite shape or volume (takes volume of container)
Plasma: highest energy. i.e.: sun and Neon lights
Energy can cause matter to change state
In nature, matter tends to most disorder (increased entropy) and lowest energy state
Entropy is a measure of the disorder.
Solid  Liquid  Gas
Least Disordered (most ordered):
Crystals (Ice/Solid)
Most Disorder (least order):
Gas/Vapor
Nature of Gases:
1. Expansion - Expand to fill container (volume specified by container)
2. Fluidity
3. Low Density
4. Compressibility - Highly compressible
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5. Diffusion & Effusion
2 or more gases  homogeneous mix in all proportions regardless of how different gases maybenot for liquids and solids
6. Deviation of Real Gases from Ideal Behavior – a real gas is a gas that does not behave completely to the
KMT
II. Pressure
A. Pressure = Force/Area
a. Flat foot – P = 1.5N/cm2
b. Toes – P = 38.5 N/cm2
c. 1 Toe – P = 77 N/cm2
B. Measure – barometer
C. Units of Pressure __________________
D. STP
III. Temperature
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IV. Gas Laws
1. Boyles Law – constant _____________
2. Charles Law – constant _____________
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Jacques Charles (1746-1823) - French Chemist
V and T (K) are directly proportional - as one goes up, the other goes up
Charles Law Example: A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas
occupy at 50° C if the pressure is constant?
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3. Gay-Lussac’s Law – constant ____________
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Joseph Gay-Lussac (1778- 1850)
P and T (K) are directly proportional – as one goes up, the other goes down
Application: car tires, cans, etc.
Example: An aerosol can has a pressure of 3.00 atm at 25°C. What is the pressure at 52°C?
4. Combined Gas Law
Microscopic
Macroscopic
Combined Problem Ex: 1 A gas measures 25.0 ml at 20.0 C and 735 mm Hg pressure. What will be its volume
at 15 C and 750 mm Hg of pressure?
5. Dalton’s Law: Example 1:
At an atmospheric pressure of 760 mm Hg, a mixture of neon with a partial
pressure of 0.250 atm, krypton with a partial pressure of 10.0 kPa and Argon. What is the partial pressure of Ar
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