3A The Greenhouse EffectWhat is a gardening greenhouse?A heater and a cover (glass or plastic cover)Hand Drawing!Earth as a greenhouseThe atmosphere acts as a coverLets light in but does not let heat outGraphics from Text: Figure 3.2, the Earth’s GreenhouseVenus has an actual average temperature of 450C vs. 100 C if no greenhouse effectEarth has an actual average temperature of 15 C vs. -18 C if no green house effectGreenhouse GassesCO2, H2O, CFCs, etc.3B Changes in CO2 Over TimeGraphics from Text: Figure 3.1, Atmospheric CO2 changes over the last 160,000 yearsNote: the correlation between temperatures and [CO2]Note: the waxing and waning of the Ice AgesHow measured?Graphics from Text: Figure 3.3, Mona Loa [CO2]Note: The seasonal variations and longer term trends in [CO2]Graphics from Text: Figure 3.4 in 2nd Edition and 3.5 in 3rd Edition, Average measured temperature changes at the earth’s surfaceHow measured?Graphics from Text: Figure 3.4 in the 3rd Edition, predicted trends in CO2 emissionsHow estimated?Dynamic Balance of CO2PhotosynthesisRespirationLonger term processesBiomassFossil FuelsCarbonate Minerals (e.g., Calcium Carbonate)Graphics from Text: Figure 3.8 in 2nd Edition and 3.9 in 3rd Edition, the Carbon Cycle3C Molecules: How They Shape UpHow do we know molecular shapes?Observed Molecular ShapesGeneral Features of StructuresComplex 3D Shapes109.5120, and 180 Bond Anglescorrelated with the number of groups around an atom1.2 – 1.55  Bond Distances (C-H  1 Correlated with Bond OrderStructural Correlations with PropertiesVSEPR, Valence Shell Electron Pair Repulsion TheoryMolecular shapes  Bond AnglesEach “thing” is an attached atom or a lone pairFour things  Tetrahedral, td, 109.5Three things  Trigonal planar, 120Two things  Linear, 180Bond DistancesSingle Bonds  Long DistancesDouble Bonds  Medium DistancesTriple Bonds  Short DistancesExampleAsk Students: Predict the bond lengths and angles in the following moleculesGroup Activity3D Vibrating MoleculesThe atoms in molecules never sit still with respect to one anotherThey constantly vibrate as if held together by springsOnce they start vibrating, the rate of vibration (i.e., its frequency) doesn’t changeEach molecules can only vibrate at certain specific frequenciesWhen a molecule is hit by a photon of light having the same energy as the energy difference between two vibration, the vibration rate will “jump up”If a vibration rate slows down to a new rate, then a photon having the energy difference will be given offVibration Frequencies and Molecular StructuresStronger bonds vibrate at higher frequenciesWeaker bonds vibrate at lower frequenciesHeavier atoms vibrate a lower frequenciesLighter atoms vibrate a higher frequenciesMolecular structure effects the number and energy of vibrationsThe balance of these trends produces molecular spectraNo two of these are identicalThe more complex the molecular structure, the greater the number of vibrations that will occurIn the Infra-Red (IR) region of the electromagnetic spectrumGraphics from Text: Figure 3.5 in 2nd Edition and 3.6 in 3rd Edition, IR Spectrum of CO2CO2 has a simple structure and therefore a simple spectrumGraphics from Text: Figure 3.6 in 2nd Edition and 3.7 in 3rd Edition, IR Spectrum of H2OH2O has a more complex structure and therefore a more complex spectrumGraphics from Text: Figure 3.7 in 2nd Edition and 3.8 in 3rd Edition, Molecular responses to various types of electromagnetic energy3E Weighing SubstancesOne can determine the weight of individual molecules or collections of moleculesSteps to calculate the Molecular Weight, MW, of the substance1st, find the atomic weight of each atom in the substance2nd, multiply the weight of each atom by the number of atoms of that type to give the total weight of each element3rd, add the total weights of all of the elements4th, this number is in AMU (Atomic Mass Units) for individual atoms and grams for moles of atomsExamples:Calculate the MW of CO2  12 + 2(16) = 44Calculate the MW of CH2F2  12 + 2(1) + 2(19) = 52One can determine the Percent Composition of individual molecules and collections of moleculesSteps to calculate Percent Composition1st, get the MW2nd, get the total weight of the element in that molecule3rd, divide the total weight of that element by the MW and multiply by 100 to get percentage4th, repeat for all elementsExample:Calculate the %C, %H, and %F of CH2F2 (remember MW = 52)%C  12 / 52 x 100 = 23.1%%H  2 / 52 x 100 = 3.8%%F  38 / 52 x 100 = 73.1%Ask Students: Calculate the MW and Elemental Compositions of the following moleculesGroup ActivityCS2MW =%C =%S =C3H2F4MW =%C =%H =%F =3F Calculating with MolesDetermining the number of moles of a substance you haveSteps:Determine the Molecular Weight of the substanceDetermine the Weight of the substanceDivide the two numbers, i.e., # Moles = Weight / MWDetermining the number of grams of a substance you haveSteps:Determine the Molecular Weight of the substanceDetermine the number of moles of the substanceDivide the two numbers, i.e., Weight = # Moles x MWExamples (For each of the following, determine the number of moles or weight of the substance, as required):For CH2F2 (MW = 52)Ask Students: For each of the following, determine the number of moles or weight of the substance, as requiredGroup ActivityCS2 20 gCS2 0.24 molesC3H2F4 11.5 gC3H2F4 11.6 moles3G Humans and CO2Ask Students: Estimate the number of tons of CO2 produced by your car each yearGroup and Board ActivitySteps:Number of gallons of gas you add each week = ?Assume each gallon of gas weighs about 4 kgAssume that the formula for gasoline is C8H18 (i.e., pure Octane)Balance the reaction for combustionFrom the number of kg of Octane, calculate the number of moles of octaneFrom the number of moles of Octane, calculate the number of moles of CO2From the number of moles of CO2, calculate its weightGiven the number of cars in the world, one can easily see that we release a lot of CO2Human effects on CO2 balancePeople release a total of about 6 - 7 billion tons per year5 billion tons from fossil fuels1 - 2 billion tons from deforestationCO2 levels290 ppm before the Industrial Revolution360 ppm in 2000net increase of 1.5 ppm per yearof total CO2 people releaseone half is lost to Biosphere and Geospherethis leaves about 3 billion tons added per year (i.e., 1.5 ppm or 740 billion metric tons)3H Methane and