Gas Laws
Chapter 14 (last one!!)
• Kinetic Molecular Theory helps explain why
gases behave differently than solids and liquids
• Gases….
1. Gas particles do not attract nor repel
each other
Kinetic Molecular Theory
2. Gas particles are much smaller than the
distances between them. This is why
gases are compressible.
Kinetic Molecular Theory
3. Gas particles are in constant random motion
and they quickly become mixed in a closed
container.
Kinetic Molecular Theory
4. Collisions between gas particles or the sides of
the container are totally elastic. There is no
kinetic energy lost
Kinetic Molecular Theory
5. If at the same temperature, all gases will have
the same kinetic energy
temperature = measure of the average
kinetic energy
Standard Temperature and
Pressure (STP)
• Normal conditions
– 0°C
• °C + 273 = Kelvin
– 1 atm
= 14.7 psi
= 101.3 kPa
= 760 mmHg
•
Overall, the Kinetic Molecular Theory is
based on four variables
1.
2.
3.
4.
•
Temperature
Pressure
Volume
Number of Particles
We can use gas laws to describe these
changes.
You’ll be able to use…
1. Boyle’s Law
•
Pressure & Volume
2. Charles’s Law
•
Volume & Temperature
3. Gay-Lussac’s Law
•
Pressure & Temperature
4. Combined Gas Law
•
Pressure, Volume, & Temperature
5. Graham’s Law of Diffusion
Boyle’s Law
• If pressure on a gas was doubled, the
volume of gas decreased by half
• Inverse relationship = one goes up, the
other goes down
Boyle’s Law
• Helps explain how we breathe
– As our ribs and diaphragm give
lungs more room to move
(increase volume) the pressure
is lowered and air comes into our
lungs
Units of Pressure
• All of these are based on atmospheres.
• Sea level = 1 atmosphere =
• =14.7 psi (pounds per square inch)
• =101.3 kPa (kilo Pascals)
• = 760 mmHg (millimeter of mercury)
Boyle’s Law
• If a gas occupies 2 Liters at 1 atm, what
will be the volume of this gas at 4 atm?
P1V1 = P2V2
2 L (1 atm) = X (4 atm)
2=4X
X = 0.5 Liters
Practice Boyle’s Law I
1. Convert 202.6 kPa to psi
2. Convert 500 mmHg to kPa
3. Convert 100 psi to mmHg
Practice Boyle’s Law I
4. Convert 3 atm to mmHg
5. Convert 50 psi to mmHg
Practice Boyle’s Law I
6. If a gas occupies 2.56 L at 1 atm, what
will be the volume of this gas at 2 atm?
Practice Boyle’s Law I
7. If 600 mL of a gas is at a pressure of 9
atm, what will be the volume at 3 atm?
Practice Boyle’s Law I
8. If 200 mL of O2 is collected at a pressure
of 5 atm, what volume will this gas
occupy at STP?
Practice Boyle’s Law I
9. A gas occupies a volume of 500 mL at
101.3 kPa. What volume will it occupy at
400 kPa?
Practice Boyle’s Law I
10. A gas occupies one liter at STP. How
much pressure (atm) would be required
to decrease the volume to 100 mL?
Practice Boyle’s Law I
11. If a gas occupies 1500 mL at 303.9 kPa,
how many atmospheres of pressure will
be needed to reduce its volume to 500
mL?
Practice Boyle’s Law I
12. If the pressure of 500 mL of a gas
changes from 800 mmHg to 120 psi,
what will be the new volume?