1. Chapter 11
Gases

2. 4 Variables that affect properties of gases
Pressure (P)
Volume (V)
Temperature (T)
Amount of gas (n)
Imagine inflating bicycle tire
Squeeze air into smaller volume
Results in pressure increasing
Increase # of collisions

3. Robert Boyle
Determined how volume of fixed amt of gas varies with pressure
Mercury added to J-shaped tube holding trapped gas at constant temp
Result - increasing pressure caused volume of trapped gas to decrease

4. Boyle’s Law Boyle’s Law (PV Law)
Volume of a given amt of gas constant temperature varies inversely with applied pressure
V  1/P
V = 1/P x C
PV = C
C is constant of proportionality

5. Graphing Boyle’s Law Graph pressure vs. volume
Downward slope
Graph pressure vs 1/volume
Straight line

6. Boyle’s Law Experiment
Take 10 measurements
Use excel to graph these points
V vs. P
V vs. 1/P
Give equation of this line
Show R squared value

7. Problem.. And a solution!
With precise measurements, Boyle’s law does not always work
No gas obeys law exactly over all ranges of temperatures and pressures
Law poorest when gas under high pressure (10 atm or more) or at low temperature (below 200 K)
Solution: An ideal gas would obey gas law exactly over all temperature and pressures

8. Jacques Alexander Charles
French Chemist and mathematician
Interested in hot-air ballooning
Study of volume of sample of gas when temperature varied, keeping pressure constant
Graph
Solid lines - where measurements made
Dotted lines - extrapolation

9. Absolute Zero
All plots of volume vs. temp extrapolated to zero, the temperature axis crosses at C
Represents at temp where gases, if not condense, would have volume = 0 or less
This is nature’s coldest temperature (absolute zero)
TK=TC
Cannot have negative volumes so this is lowest temperature!!

10. Charle’s Law (TV law) Straight line suggest
At constant pressure, volume of gas is proportional to temperature (in Kelvin)
V  T (pressure and amt of gas held constant
V = C’T

11. Gay-Lussac’s Law (PT Law)
French scientist
Studied relation of pressure and temperature of fixed amt of gas at constant volume
Exist for rigid walled container
Pressure of a fixed amt of gas held at constant temp is directly proportional to Kelvin Temperature
P  T
P = C”T