Ch2 ch304k - 1 http://astrobiology.arc.nasa.go...

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Unformatted text preview: 1 http://astrobiology.arc.nasa.go v/news/expandnews.cfm?id=10 570 http://astrobiology.arc.nasa.go v/news/expandnews.cfm?id=10 570 Chapter 2: Protecting the Ozone Layer CH304k Dr. Deb Walker Introduction The ozone layer protects life on Earth from harmful rays of the sun. What is the ozone layer? What is harmful about those rays? What do they do? How does the ozone layer protect? The ozone layer has been thinningwhy? How do we protect that which protects us? Chemistry Concepts Matter vs. Energy Allotropes Atomic Structure And MW, isotopes Lewis Structures And octet rule Bond Types E-M radiation Effect of light on matter Effect of matter on light Ozone Ozone (O 3 ) is an allotrope of oxygen. An allotrope is an alternate elemental form of a substance. Ex. C(graphite) and C(diamond) Ex. Oxygen molecule and ozone molecule Ozone in the troposphere is a pollutant. Ozone in the stratosphere is life-saving. For life as we know it. 2 Knowledge Check If there are 60 molecules of ozone for each billion molecules of air, What is the ppm of ozone? How many atoms of O are there in a two- billion molecule sample? If there are 12,000 molecules of ozone for each billion molecules of air? ppm Number of O atoms Practice If three billion oxygen molecules absorb energy and become ozone, how many ozone molecules will be formed? 3 O 2 + hv 2 O 3 If six billion? Stratospheric Ozone The Ozone Layer No, misleading. The Ozone Screen The Ozone Shield The Ozone Shield In the stratosphere Recall temperature gradient Over all Earth (not just poles) Many thin spots exist (not just South pole) Even if we could collect the ozone pollution in the troposphere and dump it into the ozone screen, it would not be enough to fix the damage thats been done. Our Fragile Shield The ozone layer protects sacrificially O 3 + hv O 2 + O Without the ozone layer, wed receive the full spectrum of energy from the sun including that which is harmful to us. Graphic (not a real photo) from http://visibleearth.nasa.gov/view_rec.php?id=9554 hv = electromagnetic energy 3 Our Fragile Shield To understand more deeply how ozone protects us, we need to know more about ozone and its interaction with light. To this end, we will study: Molecular structure (And, by association, atomic structure) hv, or electromagnetic energy Atomic Structure Atoms consist of protons, electrons, and usually neutrons. Exception? Even so, atoms consist mostly of empty space. In what ways can atoms differ from one another? Your Turn Atomic Structure Atoms can differ by Number of protons : element identity Number of neutrons : isotopes Number of electrons : ions Isotopic Symbols Mass Number Atomic Number Periodic Table as a Tool The periodic table can be used as a tool for identifying the number of protons in a...
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This note was uploaded on 05/10/2008 for the course CH 304k taught by Professor Walker during the Spring '08 term at University of Texas at Austin.

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Ch2 ch304k - 1 http://astrobiology.arc.nasa.go...

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