The Gas Laws
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
Let s examine the activity of gas molecules under different conditions http://www.falstad.com/gas/
Gas Law Simulation http://www.grc.nasa.gov/www/k-12/airplane/aglussac.html
Units of Measurement Atmospheres Pressure measured in atmospheres. 1 atm = air pressure at sea level at 25 C. Flagstaff is about 0.78 atm Another unit commonly used is the kilopascal (kpa). Sea level pressure is about 101.25 kpa. In Flagstaff it is about 79 kpa.
Units of Measurement Kelvin Temperature is measured in Kelvins (K). 0 K = absolute zero or 273.15 C Always just add 273 to whatever the temperature is in Celsius. 0 C = 273 K 25 C = 298 K Kelvin is used, because when you use proportions, you can not divide by 0 or you would get an undefined number. We want absolute differences in temperature.
Units of Measurement Liters Volume is measured in Liters 1 liter = 1000 ml. 1 ml = 1 cm 3 For the gases, we use liters because they usually occupy a much larger volume than gases.
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. P 1 V 1 = P 2 V 2
Boyles Law
Boyles Law
Boyles Law
Boyles Law
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. V 1 /T 1 = V 2 /T 2
Charles Law
Charles Law
Charles Law
Charles Law
Hot Air Balloons work on Charles Law
Hot Air Balloons work on Charles Law
Gas Law Simulations http://www.chem.ufl.edu/~itl/2045/mh_sims/gas_sim.html
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
Guy-Lussacs Law The number of particles of the substance are held constant. As you increase the temperature, the pressure will increase P 1 =P 2 T 1 T 2
Why is this a problem?
The heat will increase the pressure of the gas in the tank until it ruptures Since propane is flammable, once it can reach the oxygen in the air, it will combust
http://www.youtube.com/watch?v=hcx5k2wk6xk
Know Your Gas Laws!
Try It At Home! Seal an empty water bottle in Flagstaff Drive down to Sedona (or even better Phoenix). Why did this happen?
Try It At Home! Buy a bag of potato chips in Sedona (or Phoenix is even better) and drive back up to Flagstaff. You can use an water bottle as well
Try It At Home! Buy a bag of potato chips in Sedona (or Phoenix is even better) and drive back up to Flagstaff. You can use an water bottle as well
Combined Gas Law Combination of Boyle s, Charles, and Guy-Lussac s Laws. The number of particles of the substance are held constant. P 1 V 1 = P 2 V 2 T 1 T 2
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. If the air in the balloon is hotter than outside, then it will have a lower density and will be more buoyant. Once up high, the air is cooler and you can stay up for a long time.
Why are weather balloons not filled completely at launch?
Combined Gas Law Ground: T = 293 K P = 1 Atm V = 100 L 5,000 m: T = 263 K P = 0.5 Atm V =? 16,000 m T = 213 K P = 0.1 Atm V =? P 1 V 1 /T 1 = P 2 V 2 /T 2
Combined Gas Law Ground: T = 293 K P = 1 Atm V = 100 L 5,000 m: T = 263 K P = 0.5 Atm V =? 16,000 m T = 213 K P = 0.1 Atm V =? 1.0atm*100L = 0.5atm*V 2 293K 263K P 1 V 1 /T 1 = P 2 V 2 /T 2
Combined Gas Law Ground: T = 293 K P = 1 Atm V = 100 L 5,000 m: T = 263 K P = 0.5 Atm V = 179 L 16,000 m T = 213 K P = 0.1 Atm V =? 1.0atm*100L = 0.5atm*V 2 293K 263K V 2 = 179 L P 1 V 1 /T 1 = P 2 V 2 /T 2
Combined Gas Law Ground: T = 293 K P = 1 Atm V = 100 L 5,000 m: T = 263 K P = 0.5 Atm V = 179 L 16,000 m T = 203 K P = 0.1 Atm V =? 1.0atm*100L = 0.1atm*V 2 293K 203K P 1 V 1 /T 1 = P 2 V 2 /T 2
Combined Gas Law Ground: T = 293 K P = 1 Atm V = 100 L 5,000 m: T = 263 K P = 0.5 Atm V = 179 L 16,000 m T = 203 K P = 0.1 Atm V = 693 L 1.0atm*100L = 0.1atm*V 2 293K 203K P 1 V 1 /T 1 = P 2 V 2 /T 2 V 2 = 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, despite the cooler temperatures