1Water ChemistryBe sure to attend lab THIS week• Bring the lab manual• Must pass lab to pass this class• Instructors will give percent lab grade to one anotherSolid, Liquid, Gashttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmThree Phases of Water at Earth’s Surface•Liquid•Solid• VaporEnergy captured or released upon change from one phase to anotherSolid IceH2O(s) Icehttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmMolecular Structure of IceZumdahl, Zumdahl, DeCoste, W orld of Chemistry 2002, page 455http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP files/frame.htmLiquid WaterH2O(l) Waterhttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmGas SteamH2O(g) Steamhttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmWater Molecule• Bent molecule• Covalent bonds• Polar• Dissolves ionic substances2Properties of Water• Solid water floats on liquid water• High surface tension• ‘Universal’ solvent• High specific heat• High heat of vaporizationLiquid water molecules• In liquid phase, the water molecules fit closely together• Polar nature allows them to attract one anotherhttp://www.chemlin.net/news/2007/mar2007/water.htmHigh Surface Tensionhttp://www.webelements.com/nexus/node/786http://quest.nasa.gov/space/teachers/microgravity/6surf.htmlDissolution of ionic substanceWater Molecule• Bent • PolarWater Expansionhttp://www.elmhurst.edu/~chm/vchembook/122densityice.htmlWater Expansion• Molecule shape fit together closer in liquid• Open structured crystal due to hydrogen bonding of polar molecules upon freezingCrystal structure of ice• In solid phase of water, arrangement becomes more open, less dense • Ice floats because of this• Expansion of 9% upon freezinghttp://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htmThree phases of waterhttp://www.cdli.ca/CITE/glaciers.htm3Gas, Solid and LiquidZumdahl, Zumdahl, DeCoste, W orld of Chemistry 2002, page 441http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmWater phases and molecules Evaporation• Kinetic energy of molecules great enough to escape surface• Energy is taken from liquid—cools it• Gaseous phase or vapor phaseGas SteamH2O(g) Steamhttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmWater vaporhttp://en.wikipedia.org/wiki/Water_vaporBoilinghttp://www.chem.purdue.edu/gchelp/liquids/boil2.htmlBoilinghttp://www.deepseaimages.com/dsilibrary/showphoto.php?photo=2912&password=&sort=1&size=medium&cat=853&page=1Microscopic boilinghttp://www.chem.purdue.edu/gchelp/liquids/boil2.htmlBoiling Temp vs.Pressurehttp://www.chem.purdue.edu/gchelp/liquids/boil2.html4Pressure Cookerhttp://www.goodmans.net/get_item_ma-6qt_maitres-806212-6-qt-cooker.htmPressure cannerhttp://hgic.clemson.edu/factsheets/HGIC3020.htmBoiling at less than 100 oC• Pour in hot water• Reduce Pressure with syringehttp://www.micrecol.de/air2.htmlEvaporation or Not• Air inside glass become saturated with water and no more water can evaporate from the surface• Outside glass is open system that is not saturatedhttp://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htmCondensation• Opposite of evaporation• Kinetic energy of molecules running into surface of liquid and joining it• Heats environmentCondensation on Glasshttp://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htmAtmosphere• Evaporation – Energy goes into air– Cools remaining water• Condensation– Energy goes from air to surface– Warms local environmentAtmosphere• Warm air has greater capacity for holding water in the vapor phase• Saturation = at capacity• Relative Humidity—percent of water contained compared to saturated amount at that temperatureWater Vapor Capacityhttp://www.wdtv.com/weather/images/Weather_Review/humidity.htm5Condensationhttp://observe.arc.nasa.gov/nasa/earth/hydrocycle/graphics/condensation.jpgCondensation diagramhttp://weatherstreet.com/weatherquestions/What_is_condensation.htmSea Foghttp://www.anythingmarine.co.uk/anything/met.htmCoastal foghttp://www.victoriaweather.ca/clouds.php?image=fogEnergy of Water Phase Change• Calorie: energy to change 1 g water 1 K or 1 oC• Also need energy to change to different state of matter• Energy of vaporization/condensation¾540 calories per gram of water = 2256 J/g• Energy of melting/freezing¾80 calories per gram= 334 J/g Temperature• Measure of hotness• Celsius¾0ofreezing point of pure water at standard pressure¾100oboiling point at standard pressure• Fahrenheit¾0owas lowest attained¾32 was his age when he performed experiments¾212 is boiling point in those increments Temperature• Convert with equations¾ Order of operations Parentheses first Then multiply or divide Add or subtract last• Or use adjacent scales such as p. 142 of Conceptual Physical Science textbook32)-(F95C =32 C59F +=Temperature• Kelvin same size as degree Celsius• ‘Absolute Zero’ is 0 K¾(notice no degree symbol on K)•0oC = 273 K• Molecular motion ceases at absolute zeroBe sure to attend lab this week• Bring the lab manual• Must pass lab to pass this class• Instructors will give percent lab grade to one
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