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Unit 6
Kinetic Theory of Gases
Kinetic Theory
• 3 Parts to Kinetic Theory– All particles are in constant random motion
Kinetic Theory
• 3 Parts to Kinetic Theory– All particles are in constant random motion– The motion of one particle is unaffected by the
motion of other particles unless they collide.
Kinetic Theory
• 3 Parts to Kinetic Theory– All particles are in constant random motion– The motion of one particle is unaffected by the
motion of other particles unless they collide.– Forces of attraction among particles in a gas
can be ignored under ordinary conditions.
Kinetic Theory
The molecules move in straight lines and at constant velocity
They only change directions or speed when they collide with other molecules or the sides of the container
Boyle’s Law• As the volume of a gas decreases
(Squeezing), the pressure increases.
• The volume of gas is inversely proportional to the pressure applied.
• Temperature and number of particles are held constant.
• P1V1 = P2V2
Charles’ Law• As the temperature of a gas increases, the
volume increases.
• The volume of a gas is directly proportional to the Kelvin temperature.
• Pressure and number of particles are held constant.
• V1/T1 = V2/T2
Hot Air Balloons work on Charles Law
Hot Air Balloons work on Charles Law
Try It At Home!• Seal an empty water bottle • Throw into the freezer.
• Wait 20 minutes
Try It At Home!• Seal an empty water bottle • Throw into the freezer.
• Check it out after it gets cold!
• Charles Law in effect
Why do you always launch balloons early in the morning?
Why do you always launch balloons early in the morning?
Early morning is cooler, so the temperature difference between the air in the balloon and the outside is greater.
Once up high, the air is cooler and you can stay up for a long time.
Guy-Lussacs’ Law
• Guy-Lussacs’ Law. The number of particles of the substance are held constant.
• P1/T1 = P2/T2
Why is this a problem?
The heat will increase the pressure in the tank until it explodes
Try It At Home!• Seal an empty water bottle
on a high mountain road.• Drive down to sea level
Try It At Home!• Seal an empty water bottle
on a mountain road.• Check it out at sea level!
• Guy-Lussac’s Law
Combined Gas Law• Combination of Boyle’s and Charles’
Law. The number of particles of the substance are held constant.
• P1V1/T1 = P2V2/T2
Why are weather balloons not filled completely at launch?
Combined Gas Law
Ground:
T = 293 KP = 1 AtmV = 100 L
5,000 m:
T = 263 KP = 0.5 AtmV = ?
16,000 m
T = 213 KP = 0.1 AtmV = ?
P1V1/T1 = P2V2/T2
Combined Gas Law
Ground:
T = 293 KP = 1 AtmV = 100 L
5,000 m:
T = 263 KP = 0.5 AtmV = ?
16,000 m
T = 213 KP = 0.1 AtmV = ?
P1V1/T1 = P2V2/T2
1.0atm*100L/293K = 0.5atm*V2/263K
Combined Gas Law
Ground:
T = 293 KP = 1 AtmV = 100 L
5,000 m:
T = 263 KP = 0.5 AtmV = 179 L
16,000 m
T = 213 KP = 0.1 AtmV = ?
P1V1/T1 = P2V2/T2
1.0atm*100L/293K = 0.5atm*V2/263KV2 = 179 L
Combined Gas Law
Ground:
T = 293 KP = 1 AtmV = 100 L
5,000 m:
T = 263 KP = 0.5 AtmV = 179 L
16,000 m
T = 203 KP = 0.1 AtmV = ?
P1V1/T1 = P2V2/T2
1.0atm*100L/293K = 0.1atm*V2/203K
Combined Gas Law
Ground:
T = 293 KP = 1 AtmV = 100 L
5,000 m:
T = 263 KP = 0.5 AtmV = 179 L
16,000 m
T = 203 KP = 0.1 AtmV = 693 L
P1V1/T1 = P2V2/T2
1.0atm*100L/293K = 0.1atm*V2/203KV2 = 693 L
Why are weather balloons not filled completely at launch?
Why are weather balloons not filled completely at launch?
The Atmosphere is much thinner, so the balloon expands
Try It At Home!• Seal an empty water bottle
on a mountain road.• Check it out at sea level!
• Guy-Lussac’s Law
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