Gas LawsChapter 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. Temperature

2. Pressure

3. Volume

4. 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 = 4 X

X = 0.5 Liters

Practice Boyle’s Law I1. Convert 202.6 kPa to psi

2. Convert 500 mmHg to kPa

3. Convert 100 psi to mmHg

Practice Boyle’s Law I4. Convert 3 atm to mmHg

5. Convert 50 psi to mmHg

Practice Boyle’s Law I6. 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 I7. 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 I8. 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 I9. A gas occupies a volume of 500 mL at

101.3 kPa. What volume will it occupy at 400 kPa?

Practice Boyle’s Law I10. 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 I11. 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 I12. If the pressure of 500 mL of a gas

changes from 800 mmHg to 120 psi, what will be the new volume?