The Future (?) Data from past 100 years: CO 2 conc. has risen by 25% average temp. increase: C Current: doubling the CO 2 conc.  C ( F by 2100) CO 2 is a major part of the greenhouse effect Earth’s average temperature is increasing

Shape of Molecules (3.3) Greenhouse gases: CO 2, CH 4, N 2 O, O 3, H 2 O, CFCs Not greenhouse gases: O 2, N 2, Ar Why the difference? Shape!

VSEPR Lewis structures: 2D Reality: 3D Bonds are made of electrons  Negatively charged  Repel each other (still attracted to protons)  Want to be as far apart as possible!

Example: Methane CH 4 : tetrahedral C H H H H H H H H C

Fig.3.7

Fig.3.8

Fig.3.9 “Trigonal Pyrimidal”

Fig.3.10 “Bent”

Fig.3.11 “Linear”

Fig “Bent”

Light and Molecules (3.4) UVB, UVC: Bonds break IR: Can’t break (not enough energy) Can cause vibrations Shape  HOW a molecule can vibrate Which wavelength? Bond strength & flexibility, atom masses

Fig.03.13

Fig.3.14

What about O 2 and N 2 ?  Do not absorb IR radiation  IR does not cause vibration  Can’t “trap” heat  Not greenhouse gases

Fig.3.16

The Carbon Cycle Sect. 3.5

Fig Where does CO 2 come from? Where does it go?

Sources of CO 2 CaCO 3 (limestone) water Plants & animals Respiration/decay Volcanic vents CO 2 (natural)

Consumption of CO 2 CO 2 Plants Respiration water H 2 CO 3 Pressure/time Fossil Fuels Mineral Dep.

Fossil Fuel Contribution to Atmospheric CO 2 : 6-7 billion tons of carbon released ~ ½ goes to atmosphere Since 1860: – CO 2 conc. 290 ppm  375 ppm, – Increases ~1.5 ppm/year.

Deforestation Adds CO 2 to air (burning/decay) Takes away a CO 2 remover (trees/plants)

Excess CO 2  global warming Increase in atmos. CO 2 is a concern – Gt of carbon/year How much CO 2 is added per year?

Quantitative Concepts: Mass (3.6) How much does an atom weigh? Depends on the atom Standard: Carbon-12 Mass # Atomic #: 6 6p, 6n One Carbon 12 = 12 amu

C 6 Carbon Atomic # Symbol Name Atomic Mass

Carbon: 3 isotopes Carbon-12: 98.89% Carbon-13: 1.11% Carbon-14: ~0.00% Average atomic mass for C = amu What’s with the 12.01??? Atomic mass is an average of all carbon atoms

NO carbon atoms weigh amu Treat ALL carbon atoms as though they weigh Tbs of carbon has about x carbon atoms – 602,200,000,000,000,000,000,000 Dealing with large numbers of atoms – Average is best