Chem 102 1st Edition Lecture 23Outline of Last Lecture I. Detecting RadioactivityII. Energy in Nuclear ReactionsIII. Fusion/FissionIV. Radiation EffectsOutline of Current LectureI. AtmosphereII. Coverage Gap and OzoneCurrent LectureI. Atmosphere- 4 Layers, controlled by temp and pressure, with boundaries:-Troposhpere- 0-12km, everything on Earth is located here. This is the weather zone. Increase altitude, decrease temp. Sun heats Earth’s surface, which in turn give off heat and warm the air. Hot air rises, cool air sinks creating circulation patterns called convection cell which is responsible for all surface wind and weather. -Stratosphere- 12-50km, contains the ozone layer, protects us by absorbing UV light. Increase altitude, increase temp. Ozone absorbs sunlight and gets hot.-Mesosphere- 50-85km, no ozone, aurora layer. Increase altitude, decrease temp. Far from surface and lacks ozone.-Thermosphere- 85km and up, O and N exist as single atoms that absorb UV radiation.Increase altitude, increase temp.-Pressure decreases with increasing altitude. Due to gravity the makeup of atmospheric layers are not uniform. Ppm(gas)= (volume(part)/ volume (total)) x 10^6-Boundaries between layers are denoted as “pauses” gases slowly mix here. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-The sun gives off a wide range of harmful radiation, all with different energies. Atomsand molecules in outer layers protect us by absorbing these energies before they reach the troposphere. E=hV or hc/wavelength-In order to absorb energy, incoming energy must be sufficient to break chemical bonds or remove an electron from an atom or a molecule, and the atom or molecule must be able to absorb the energy. -If the energy is too high it causes molecules to react. Photodissociation- Absorption of energy results in the cleavage of a chemical bond. Resulting in 2 electronically neutral particles. Incoming energy> Ebond, then the bond will break. -In thermosphere amount of O2 varies, because much of solar high energy radiation isabsorbed by O2 before it reaches the atmosphere. N does not absorb this so very little atomic N is formed in upper atmosphere photodissociation. -Photoionization- Absorption of energy resulting in the ejection of an electron. 4 important processes occur above 90km creating positively charged ions. II. Coverage Gap and Ozone- N2 and O2 protect us from radiation. <240nm wavelength, but what protects us from energy between 240<nm<400? Stratosphere, the ozone layer absorbs light. -Ozone is formed when Oxygen collides with O2, O3 must collide with something (M) to relieve energy to prevent decomposing. Photodissociation of O3 reverses its formation, thus Ozone has a cycle. This solar radiation is converted to thermal energy this is why temp increases in the stratosphere. -The atmosphere is altered by human and natural factors. Natural is things such as volcanoes which can decrease ozone. Population growth causes ozone depletion, pollutants and greenhouse gases. -Depletion of ozone layer- ozone has a hole, caused by CFCs. CFCl3 and CF2Cl2 are notin nature, used in spray cans, refrigerants and air conditioners. CFCs are unreactive and insoluble in H2O so they cannot be removed. -Stratospheric CFCs photodissociate and Cl2 atoms react with ozone. -Reduce Ozone depletion? Replace CFCs with fluorocarbons. C-H bonds replace C-Cl