1Water PropertiesProperties of Water• Solid water floats on liquid water• High surface tension• ‘Universal’ solvent• High specific heat• High heat of vaporizationSolid, Liquid, Gashttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmWater Molecule• Bent moleculeCltbd•Covalent bonds• Polar• Dissolves ionic substancesLiquid water molecules• In liquid phase, the water molecules fit closely together• Polar nature allows them to attract one another• Most dense at 4°Chttp://www.chemlin.net/news/2007/mar2007/water.htmLiquid WaterH2O(l) Waterhttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmHigh Surface Tensionhttp://www.webelements.com/nexus/node/786http://quest.nasa.gov/space/teachers/microgravity/6surf.htmlDissolution of ionic substanceWater Molecule• Bent Pl•Polar2Solid IceH2O(s) Icehttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmMolecular Structure of IceZumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 455http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP files/frame.htmWater 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.htmThree Phases of Water at Earth’s Surface• Liquid• Solid• VaporEnergy captured or released upon change from one phase to anotherGas SteamH2O(g) Steamhttp://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmGas, Solid and LiquidZumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 441http://www.unit5.org/christjs/Matter%20and%20Energy/Unit%202%20PP_files/frame.htmWater phases and molecules3Evaporation• Kinetic energy of molecules great enough to escape surface• Energy is taken from liquid—cools itGh h•Gaseous phase or vapor phaseWater vaporhttp://en.wikipedia.org/wiki/Water_vaporEvaporation or Nothttp://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htm• Air inside glass become saturated with water and no more water can evaporate from the surface• Outside glass is open system that is not saturatedBoilinghttp://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 Temperature• For any given pressure, there is a temperature at which water boils• The temperature of the water remains at that temperature until all of the water hasthat temperature until all of the water has been changed from liquid to vapor• The length of time for this to occur does not have an effect on this temperatureBoiling Temp vs.Pressure http://www.chem.purdue.edu/gchelp/liquids/boil2.htmlPressure Cookerhttp://www.goodmans.net/get_item_ma-6qt_maitres-806212-6-qt-cooker.htm4Pressure cannerhttp://hgic.clemson.edu/factsheets/HGIC3020.htmBoiling at less than 100 oC• Pour in hot water• Reduce Pressure with syringehttp://www.micrecol.de/air2.htmlCondensation• Opposite of evaporation• Kinetic energy of molecules running into surface of liquid and joining itHt i t•Heats environmentCondensation on Glasshttp://www.geology.sdsu.edu/classes/geol351/01watercycle/watercyclefigs.htmAtmosphere• Evaporation – Energy goes into air– Cools remaining waterCd ti•Condensation– Energy goes from air to surface– Warms local environmentAtmosphere• Warm air has greater capacity for holding water in the vapor phase• Saturation = at capacityRlti H idittf t•Relative Humidity—percent of water contained compared to saturated amount at that temperatureWater Vapor Capacityhttp://www.wdtv.com/weather/images/Weather_Review/humidity.htmCondensationhttp://observe.arc.nasa.gov/nasa/earth/hydrocycle/graphics/condensation.jpgCondensation diagramhttp://weatherstreet.com/weatherquestions/What_is_condensation.htm5Sea 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 matterstate 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 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 divideAdd or subtract last32)-(F95C =9Add or subtract last• Or use adjacent scales such as p. 142 of Conceptual Physical Science textbook32 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
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