Oxygen, Ozone and wavelength ( you tube )

1. Oxygen, Ozone and wavelength (you tube) Like the oxygen molecule, ozone is broken apart through absorption of ultraviolet (UV) photons. A photon is a packet of energy that has a particular wavelength. Ultraviolet light has wavelengths of 1 nm to 400 nm. In the case of oxygen molecules, the bond is quite strong (e.g., the tennis balls are joined with Krazy glue). Hence, the photon required to break this bond must be very energetic. The chemical bonds between the oxygen atoms in ozone, however, are much weaker than those found in molecular oxygen (e.g., the tennis balls are joined with Scotch tape). As a result, less energetic photons, meaning those with longer wavelengths, can break apart ozone molecules.

2. Ozone absorption of UVsources: cleaning solvents, halons, aerosols, refrigerants, foam blowers • "The ozone layer" refers to the ozone within stratosphere, where over 90% of the earth's ozone resides. Ozone is an irritating, corrosive, colorless gas with a smell something like burning electrical wiring. In fact, ozone is easily produced by any high-voltage electrical arc (spark plugs, Van de Graaff generators, Tesla coils, arc welders).

3. CFC’s and OzoneCFC’s break down: CCl2F2 + uv light  •CClF2 + •Cl • In the lower atmosphere, CFCs are protected from UV light from the ozone layer in the stratosphere. But as CFCs rise, they move into the stratosphere. The UV light in the stratosphere breaks up the CFCs. They release chlorine, and these free chlorine atoms rip oxygen atoms off of ozone, leaving ordinary oxygen gas. Cl • + O3 -> ClO• + O2 Chlorine free radical+ Ozone -> chlorine monoxide +oxygen gas • This would not be a huge problem, except for one thing: chlorine monoxide will collide with free oxygen atoms (O1). This oxygen atom will break apart the chlorine monoxide, releasing the chlorine atom back into the stratosphere to degrade more ozone. The chlorine atoms keep cycling through the process of breaking up ozone, and it has upset the balance of the ozone system. This reaction happens over and over again, allowing one chlorine atom to destroy many ozone molecules. ClO• + O -> O2 + Cl• Chlorine monoxide free radical + oxygen atom -> oxygen gas + chlorine free radical, which in effect makes the chlorine act as a catalyst View Animation

4. Ozone Depletion by NOxOverall Reaction: NO2 + O3 NO + 2O2 • Nitrous oxide is emitted as a byproduct of agricultural fertilization, livestock manure, sewage treatment, and supersonic jet aircraft engines. • In nature, bacteria in soil and the oceans break down nitrogen-containing compounds, releasing nitrous oxide. • About one-third of global nitrous oxide emissions are from human activities. • Nitrous oxide, like CFCs, is stable when emitted at ground level, but breaks down when it reaches the stratosphere to form other gases, called nitrogen oxides, that trigger ozone-destroying reactions. Mechanism: NO2 + uv light  NO + O• (g) O• + O3(g) 2O2 (g)

5. Effects on Polar Regions • the "ozone hole" is an area over the south pole where lower than normal levels of ozone have been detected. • the amount of ozone in this layer varies naturally throughout the year because it is formed and destroyed by chemical reactions that require light. • So the ozone hole is more intense when there is sunlight over the south pole then where then is darkness (i.e., the austral winter). • Human activities have made the hole much more intense, but as far as we know there was always a lower amount of ozone over the south pole deep blue colors signify the lowest ozone how the hole has changed over time at the maximum annual hole size (which happens in October). The lowest ozone is shown with purple colors in this image.