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Unit 9 Independent particles, moving in straight lines Change direction with collisions Travel randomly Assume shape of container and volume of their container Large amount of empty space Compressible No attractive forces between particles Fluidity – gas particles glide and flow past each other Expansion – fill any container Compressibility – can decrease the volume Diffusion – spontaneous mixing of two gases, flow until evenly distributed. Flow from an area of high concentration to an area of low concentration. Dependent on the force of the collision and the number of collisions that occur between particles. Pressure = Force/Area Atmospheric or barometric pressure – results from collisions of air molecules with objects on earth. Manometer Barometer Developed by Evangelista Torricelli Pressure gauge SI unit = Pascal (Pa) A pascal is small so normally the kilopascal (kPa) is used which is 1000 Pascal. Atmosphere (atm) 1 atm is the atmospheric pressure at sea level. Pounds per square inch (psi) Millimeters of mercury (mmHg) Torr Named after Robert Boyle It says that at a constant temperature pressure and volume are inversely proportionate. As volume goes up the pressure goes down and vice versa. P1V1=P2V2 Weather Balloon Helium vs. Air Equilibrium Airplanes Pressure as you climb Volume Bike Pump The maximum volume of air that a weather balloon can hold without rupturing is 22,000L. It is designed to reach an altitude of 30 km. At this altitude, the atmospheric pressure is o.o125 atm. What maximum volume of helium gas should be used to inflate the balloon before it is launched? Two liters of air at atmospheric pressure are compressed into the 0.45 L canister of a warning horn. If its temperature remains constant, what is the pressure of the compressed air in the horn? Named after Jacques Charles States that at a constant pressure the volume of a gas is directly proportional to its kelvin temperature. As temperature goes up volume goes up. 𝑉1 𝑉2 = 𝑇1 𝑇2 Temperature must be in Kelvin: K=oC +273 Lid in refrigerator Air hot Cools down and sinks Tires on the road Too inflated pops tire Balloon A balloon is filled with 3.0 L of helium at 22oC and 760 mmHg. It is then placed outdoors on a hot summer day when the temperature is 31 oC. If the pressure remains constant what will the volume of the balloon be? Named after Joseph Gay-Lussac States that at a constant volume the pressure and temperature of a gas are directly proportional. As temperature goes up pressure goes up. 𝑃1 𝑃2 = 𝑇1 𝑇2 Temperature must be in Kelvin: K=oC +273 Aerosol can in fire Pressurized can Increase temp= explosion All three gas laws put together. 𝑃 1 𝑉1 𝑃 2 𝑉2 = 𝑇1 𝑇2 Temperature must be in Kelvin: K=oC +273 STP = Standard Temperature and Pressure Defined as 273K and 1 atm A toy balloon has an internal pressure of 1.05 atm and a volume of 5.0L. If the temperature where the balloon is released is 2ooC, what will happen to the volume when the balloon rises to an altitude where the pressure is 0.65 atm and the temperature is -15 0C? Hyper: above or excessive Hyperbaric refers to pressure that is greater than normal Hyperbaric chambers uses: cure burns Decompression sickness Anemia Infections