1. A Little Gas Problem
Ideal Gas Behavior

2. Basic Kinetic Molecular Theory
Basic states of matter: solid, liquid, gas, and plasma (not emphasized)
Particles held together by intermolecular forces- essentially positive-negative attractions

3. Solids versus Liquids Closely-packed particles High density
Definite shape
Definite volume
High structure/order
Low molecular speed
Many intermolecular connections
More spacing between particles
Definite volume
No definite shape
Less structure/order
Higher molecular speed
Some intermolecular bonds broken
Solids:
Liquids:

4. Click here for simulation
What about the gases
Wide-open spaces
Very low density
Shape of container
Volume of container
Randomness/chaos
High molecular speed
No molecular connections
Gases or vapors
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5. Solids, liquids & Gases Gases: loose and free, fast and furious
Liquids: layers, some structure and attachment
Solids: structure, restricted motion, order

6. How does this all work?
In solid form the molecules have low energy, many connections and little motion
Energy added, more moving, connections broken
Faster means spreading out and breaking connections

7. What gases are like… Particles are widely spread out
They move freely and independently
Many collisions occur
Some particles are super fast
Some are super slow
Most are “average”
Collisions exert pushes

8. As the molecules move they collide
Molecules collide with each other with energy being transferred
Molecules collide with sides of container
Newton’s 3rd law: action/reaction

9. How gases exert pressure
Molecules collide and “push off” the container
Each push is a force
Force is over an area
Pressure = F/A
Pressure units:

10. Handling the pressure Common units: psi, kPa, atm, torr, mm Hg
Measured with a barometer
Closed-end barometer
Open-end barometer

11. Calculating pressures from barometric data
For a closed-end barometer (manometer): the pressure is the difference between Hg levels
For a open-end barometer: the pressure is the atmospheric pressure + the difference in the columns of Hg