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u9 - Chemistry Unit 9 The Gas Laws The Atmosphere an ocean...

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Unit 9: The Gas Laws Chemistry
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~78% The Atmosphere an “ocean” of gases mixed together Composition nitrogen (N2)………….. oxygen (O2)…………… argon (Ar)……………... carbon dioxide (CO2)… water vapor (H2O)……. Trace amounts of: ~21% ~1% ~0.04% ~0.1% He, Ne, Rn, SO2, CH4, NxOx, etc.
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Depletion of the Ozone Layer O3 depletion is caused by chlorofluorocarbons (CFCs). Uses for CFCs: refrigerants Ozone (O3) in upper atmosphere blocks ultraviolet (UV) light from Sun. UV causes skin cancer and cataracts. O3 is replenished with each strike of lightning. aerosol propellants -- banned in U.S. in 1996 CFCs
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The Greenhouse Effect CO2 MOLECULES Upon contact with objects, some of light’s energy is released as heat. Lower energy, longer λ λιγ ητ ισ βλοχκεδ βψ ΧΟ2 ανδ ΧΗ4; ενεργ ψ δοεσν τ εσχαπε ιντο σπαχε; ατμοσπηερε ηεατσ υπ. High energy, short λ λιγ ητ πασσεσ εασιλψ τηρουγ η ατμοσπηερε. Energy from Sun has short wavelengths ( λ s) and high energy. CO2 and methane (CH4) let this light in. Reflected light has longer λ s and less energy. CO2 and CH4 (“greenhouse gases ”) prevent reflected light from escaping, thus warming the atmosphere.
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Why more CO2 in atmosphere now than 500 years ago? _______________________________ -- -- -- -- -- -- -- burning of fossil fuels deforestation urban sprawl wildlife areas rain forests coal petroleum natural gas wood * The burning of ethanol won’t slow greenhouse effect.
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What can we do? 1. Reduce consumption of fossil fuels. At home : On the road : 2. Support environmental organizations. 3. Rely on alternate energy sources. insulate home; run dishwasher full; avoid temp. extremes (A/C & furnace); wash clothes on “warm,” not “hot” bike instead of drive; carpool; energy-efficient vehicles solar, wind energy, hydroelectric power
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The Kinetic Molecular Theory (KMT) -- -- deals w/“ideal” gas particles… 1. …are so small that they are assumed to have zero volume 2. …are in constant, straight-line motion 3. …experience elastic collisions in which no energy is lost 4. …have no attractive or repulsive forces toward each other 5. …have an average kinetic energy (KE) that is proportional to the absolute temp . of gas (i.e., Kelvin temp.) explains why gases behave as they do as Temp. , KE
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Theory “works,” except at high pressures and low temps. (attractive forces become significant) N2 can be pumped into tires to increase tire life KMT “works” liquid nitrogen (N2); the gas condenses into a liquid at –196oC KMT starts to break down –196oC H2O freezes 37oC 100oC 0oC H2O boils body temp. liquid N2
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** Two gases w/same # of particles and at same temp. and pressure have the same kinetic energy. KE is related to mass and velocity (KE = ½ m v2). More massive gas particles are _______ than less massive gas particles (on average).
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