2. Absolute Zero
Theoretical temperature of a gas when its pressure is zero
Kelvin scale – temperature scale where 0 K is absolute zero
One degree change in Kelvin is the same as one degree change in Celsius
Conversion: K = oC + 273
There are no negative temperatures in Kelvin!
For this unit, ALWAYS use Kelvin!

3. Kinetic Molecular Theory
(How gas molecules behave)
Very small particles
Distances between particles are large
In constant, random motion
Collisions are perfectly elastic
Kinetic energy (energy of motion) depends of temperature of gas
Particles exert no force on each other

4. Pressure Force of a gas over an area
Related to number of collisions of molecules
Pressure exerted by air = atmospheric pressure

5. Units for Pressure Atmospheric Pressure is: 1 atmosphere = 1 bar
101,325 Pascal (Pa)
kiloPascals (kPa)
760 mm Hg
760 torr
14.7 psi

6. Marshmallow Man Explain why he gets bigger, then shrinks!
He gets larger because the air molecules in the marshmallow take up more space
Gets a little smaller while still in the low pressure container because gas molecules escape
Gets much smaller when back to atmospheric pressure

7. Gas Laws Boyle’s Law: P1V1=P2V2 Lussac’s Law: P1/T1 = P2/T2
Charles’ Law: V1/T1 = V2/T2
All Temperatures must be in Kelvin! (oC+273)
(otherwise your proportions will be off!)

8. Pick your equation, then solve…
A gas occupies 3.3 L of space at 25oC. It was warmed to 75oC. How much space does it take up?
A container has three gases: O2, N2, and He. Their partial pressures are 2 kPa, 3.5 kPa, and 7 kPa. What is the total pressure?
What would the volume be if you have 15 g of O2 at STP?