Today (Tues 3/3)

1. Today (Tues 3/3) • Chapter 2 Homework Due • Newspaper Articles: Jeremy Hendrickson and Matt Wood • Molecular Shape Activity • Start Chapter 3 notes • Laboratory: Greenhouse Gases Lab

2. Review: How to draw Lewis structures . . . . . . . . . . . . 1. Determine the sum of valence electrons. CH4 CCl4 C: 4 Valence electrons H: 1 Valence electron *4 atoms Total: 8 electrons C: 4 Valence electrons Cl: 7 Valence electron *4 atoms Total: 32 electrons • Use a pair of electrons to form a bond between each pair of bonded atoms. Cl Cl Used 8 in each Cl Cl • Arrange the remaining electrons to satisfy octet rule. .. Cl .. .. .. .. Cl Cl Used 8 .. Used 32 Cl

3. Molecular Shape Activity

4. Fig. 3.11 – Carbon Dioxide Space-fillingCharge- density Lewis structuresshow connectivity.

5. Fig. 3.8 - Methane This Lewis structure is drawn in 3-D.

6. Figure 3.9: Ammonia

7. Fig. 3.10 - Water

8. Nitrate Ion, NO3-

9. Fig. 3.12 - Ozone

10. Summary of Molecular Shape Activity: Valence Shell Electron Pair Repulsion Theory • Assumes that the most stable molecular shape has the electron pairs surrounding a central atom as far away from one another as possible. • Molecules can be classified into shape categories. • If there are lone pairs on the central atom, the bond angles will be smaller than predicted.

11. Chapter 3: The Chemistry of Global Warming

12. Chapter 3 Learning Objectives • The greenhouse effect • Molecular structure and shape • Why are some molecules greenhouse gases (absorb IR radiation) • Molecular vibrations • Moles • Enhanced Greenhouse Effect andGlobal Climate Change • Global Climate Change Models • Global Climate Change Policy

13. The Earth’s Energy Balance Greenhouse effect Our atmospheric gases trap and return a major portion of the heat radiating from the Earth. It is a natural, necessary process. Figures Alive

14. What makes a gas a greenhouse gas? • IR absorption is related to molecular structure • Dipole moment – separation of charge • Electron density is not uniform in the molecule resulting in partial electrical charges

15. O O O H H H O O O C H H C H Which of the following molecules have a dipole moment? H2O, CO2, O3, and CH4

16. To absorb IR radiation… • Energy of IR radiation must match the vibration energy of the molecule • For us to see absorbtion of IR radiation on a spectrometer the dipole moment (charge distribution) must change • IR Tutor • Units on IR spectra are wavenumbers, cm-1 • Wavenumber = 1/wavelength (in cm)

17. Fig. 3.14 – IR spectra of CO2

18. Fig. 3.15 – IR spectra of H2O Stretching Bending

19. Why aren’t O2 and N2 greenhouse gases? Why doesn’t the IR radiation coming from the sun also cause a greenhouse effect?

20. Today (Thurs 3/5) • Newspaper Articles: Eric Noun and Steve Andres • Chapter 3 notes: ‘review and new’ • Focus Group project – Evaluation of Example Papers

21. Chapter 3 Learning Objectives • The greenhouse effect • Molecular structure and shape • Why are some molecules greenhouse gases (absorb IR radiation) • Molecular vibrations • Moles • Enhanced Greenhouse Effect andGlobal Climate Change • Global Climate Change Models • Global Climate Change Policy

22. The Earth’s Energy Balance Greenhouse effect Our atmospheric gases trap and return a major portion of the heat radiating from the Earth. It is a natural, necessary process. Figures Alive

24. What makes a gas a greenhouse gas? • IR absorption is related to molecular structure • Dipole moment – separation of charge • Electron density is not uniform in the molecule resulting in partial electrical charges

25. O O O H H H O O O C H H C H Which of the following molecules have a dipole moment? H2O, CO2, O3, and CH4 dipole moment dipole moment no dipole moment no dipole moment

26. To absorb IR radiation… • Energy of IR radiation must match the vibration energy of the molecule • For us to see absorbtion of IR radiation on a spectrometer the dipole moment (charge distribution) must change • Units on IR spectra are wavenumbers, cm-1 • Wavenumber = 1/wavelength (in cm)

27. Fig. 3.14 – IR spectra of CO2

28. Fig. 3.15 – IR spectra of H2O Stretching Bending

29. The Greenhouse Effect • Established • Proven • Fact • Not controversial • Temperature of the earth would be ~60 F cooler without the Greenhouse Effect • Global Warming is the theory that the greenhouse effect has been enhanced by carbon dioxide and other greenhouse gases

30. Amplification of Greenhouse Effect: Global Warming: What we know 1. CO2 contributes to an elevated global temperature. 2. The concentration of CO2 in the atmosphere has been increasing over the past century. 3. The increase of atmospheric CO2 is a consequence of human activity. 4. Average global temperature has increased over the past century. 3.2

31. What might be true: 1. CO2 and other gases generated by human activity are responsible for the temperature increase. 2. The average global temperature will continue to rise as emissions of anthropogenic greenhouse gases increase. 3.8

32. Loss of Polar Ice Cap NASA Study: The Arctic warming study, appearing in the November 1 2003 issue of the American Meteorological Society's Journal of Climate, showed that compared to the 1980s, most of the Arctic warmed significantly over the last decade, with the biggest temperature increases occurring over North America. 1979 2003 Perennial, or year-round, sea ice in the Arctic is declining at a rate of nine percent per decade. 3.9

33. Loss of Polar Ice Cap 1979 As the oceans warm and ice thins, more solar energy is absorbed by the water, creating positive feedbacks that lead to further melting. Such dynamics can change the temperature of ocean layers, impact ocean circulation and salinity, change marine habitats, and widen shipping lanes. 2003 3.9

34. The snows of Kilimanjaro 82% of ice field has been lost since 1912 3.9

35. Main greenhouse gases • Water vapor • Carbon dioxide*** • Methane • Chlorofluorocarbons (CFCs) • Tropospheric ozone • Nitrous Oxide N2O

36. Carbon Cycle Fig. 3.17

37. Fig. 3.4 CO2 and Temperature

38. McMurdo Station, Antartica Ice Core Ice Layers Drilling Tent

39. CO2 concentrations by ice core and IR data Fig. 3.5

40. Cool Links • IR spectra of CO2 and other GHGs http://chemistry.beloit.edu/Warming/pages/infrared.html • NOAA: National Oceanic and Atmospheric Administration • Measuring CO2 • Ice Core Data • Oceans Warming http://www.esrl.noaa.gov/gmd/ccgg/about/co2_measurements.html http://www.ncdc.noaa.gov/paleo/icecore.html http://www.noaanews.noaa.gov/stories/s399.htm • National Glaciology Group, Canada http://cgc.rncan.gc.ca/glaciology/national/drill_e.php

41. CO2 trends • CO2 increasing ~2.1 ppm/yr (for 2001-2005) • 1963 increase = 0.76 ppm • 1998 increase = 2.87 ppm (biggest leap) • 2002 increase = 2.1 ppm • 2007 increase = 2.4 ppm http://www.esrl.noaa.gov/gmd/publications/annmeet2006/pdf_2006/talks%202006%202.pdf

42. Today (Tues 3/10) • Newspaper Presentations: Brock Hill and Andrew Griesman • GHGs and IR Spectra (Lab Prep) • Library Time (~3-4:20) For Next Time (Thurs 3/12) • Print new slides (I added some to the end) • Read Chapter 3 • Work on Homework 3

43. Why is CO2 increasing? • Burning fossil fuels converts the carbon in the fuels to carbon dioxide (CO2) • Fossil fuels = coal, gasoline, natural gas • Actually CO2 levels have not increased in the atmosphere as much as predicted • Also been contended that CO2 levels have increased due to temperature increasing • Scientific understanding is key – models developed

44. CO2 IR Spectra

45. Tab. 3.2

46. Methane • Sources: • ~40 % Natural Sources • Natural Gas escaping from rocks • Decaying plant material in wetlands • Agriculture • Rice Paddies (Anaerobic Bacteria) • Cattle (~500 L of CH4 per day!) • Landfills • Termites • Release from oceans, bogs, permafrost

47. IR Spectra of Methane CO2 Contamination

48. Laughing Gas, N2O • Sources • Bacterial removal of nitrate ion (NO3-) from soils • Ocean upwelling • Statrospheric reactions • NH3 fertilizers • Catalytic converters

49. IR spectra of Water vapor CO2 Contamination

50. IR Spectra of some GHGs