Class16

Class16 - Water and Related Technologies Water Fluoridation...

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Unformatted text preview: Water and Related Technologies Water Fluoridation Soaps and Detergents Bottled Water Potable water is necessary for the survival of living matter Water makes up 50-90% of the weight of most life-forms Roles: solvent that carries food to cells and waste from cells Survival time: about 1 week without water, but two weeks without food In addition to individual survival, water serves as the basis of many technologies Buell/Girarad, Chemistry, 2nd,Jones and Bartlett, MA,2003,282 http://ga.water.usgs.gov/edu/graphics/wateruse2000pie.gif Consumption and uses of water in US US daily consumption (400 B gallons) US daily household consumption (300 gallons) Water cycle is the source of water www.italocorotondo.it/.../ hydrological_cycle.htm Salt water http://www.unep.org/dewa/vitalwater/jpg/0101-water-quantity-EN-2.jpg The total volume of water on earth is large, but water that can readily be made potable is not Runoff water is best source for municipal water, then groundwater, then saltwater. Run-off water requires the least treatment to make it potable Runoff water has the least dissolved salts It may be contaminated with suspended matter such as finely divided clay, fertilizer, organic pesticides from farming, bacteria from animals, and odors from decaying living matter Typically runoff water can be made potable by treatment with aluminum sulfate, lime, activated charcoal, and chlorine as shown on the next slide Hill/Kolb, Chemistry, 10th, Prentice-Hall,2004, 376 Al(OH) 3 removes suspended matter Charcoal removes organic substances (with charcoal) Aeration removes odors Cl 2 kills bacteria Simple chemical technologies are used to make surface water potable Many cities also add fluoride to drinking water to decrease tooth decay Enamel consists of closely- packed rods of hydroxyapatite: Ca 5 (OH)(PO 4 ) 3 Dentin is bone-like matter Pulp chamber contains blood vessels and nerves http://www.colgate.com/app/Colgate/US/OC/Information/OralHealthBasics/CommonConcerns/Cavities/IllustrationsHowAToothDecays.cvsp Structure of a Human Tooth http://www.elmhurst.edu/~chm/vchembook/548toothdecay.html Bacteria in saliva produce acids from sugars Enzymes Digestion of table sugar Bacteria Conversion of sugar to acid Acid production by bacteria is rapid Radel/Navidi Chemistry, 2nd, West,1994,834 [H + ] (Increasing acidity) Time (min) after exposure to dilute sugar solution 10-7 10-6 10-5 10-4 Bacteria convert sucrose to lactic acid which can demineralize some enamel: 4H + + Ca 5 (OH)(PO 4 ) 3 5 Ca 2+ + 3HPO 4 2- + H 2 O. This leaves an opening for bacteria to invade tooth. http://www.hivdent.org/_peag/faq-deca.htm http://www.colgate.com/app/Colgate/US/OC/Information/OralHealthBasics/CommonConcerns/Cavities/IllustrationsHowAToothDecays.cvsp Acids attack enamel Fluoridation reduces/reverses decay of enamel Ca 5 (OH)(PO 4 ) 3 + F - => OH - + Ca 5 (F)(PO 4 ) 3 In places where decay has started, the F - ion deposits in the openings left by the departure of OH...
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This note was uploaded on 10/19/2011 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Class16 - Water and Related Technologies Water Fluoridation...

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