1Heat and Energy TransferEnergy of Phase ChangeTemperature• 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 zeroHeat• Calorie– Amount of heat required to raise the temperature of 1 gram of pure water 1oC– Food ‘Calories’ are kilocalories• Joule ~ ¼ of calorie– 1 cal. = 4.184 JLaws of Thermodynamics1. Heat added = increase in thermal energy + external work done by the system2. Heat never spontaneously flows from a cold substance to a hot substance3. No system can reach absolute zeroSpecific Heat Capacity• Quantity of heat needed to change the temperature of given amount of a substance 1oC• Water—very high specific heat capacity– Maritime areas more mild temperature than continental areas– Takes 1/8 calorie to raise temperature of iron 1oCHeat Expansion• Random motion causes substance to be bigger• Liquids usually have greater heat expansion than solids• Thermostats use different expansion of different type of metalshttp://www.alaskarails.org/terminology/questions.html http://demo.physics.uiuc.edu/LectDemo/scripts/demo_descript.idc?DemoID=40Water Expansion• Unusual response to cooling• Contracts until reaching 4oC• Expands slightly upon further cooling to 0oC• Expands 9% upon freezing2Water Molecule• Bent • PolarWater Expansion• Molecule shape fit together closer in liquid• Open structured crystal due to hydrogen bonding of polar molecules upon freezingHeat Transfer: conduction• Tile is a better conductor of heat than the wood floorHeat Transfer: convection• Currents from heater shown by shadowsHeat Transfer: radiation• Does not need material to transfer radiant energy• Dark bodies absorb it better than light-colored onesRadiant Energy• All objects emit thermal energy– Visible light above ~500oC– Re-emit absorbed radiation at wavelength according to temperature • Good absorbers are good emitters• Poor absorbers are poor emittersHeat Transfer• Conduction– Direct molecule interaction– Transferring energy to next molecule• Convection– Movement of fluid: liquid or gas• Radiation– Through open space– Electromagnetic radiationEnergy 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 Energy of phase change for waterhttp://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html3Solid 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.htmThree phases of waterhttp://www.cdli.ca/CITE/glaciers.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.htmCondensationAs air rises, it expands and coolsCondensation of water vapor occurshttp://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.htm4Coastal foghttp://www.victoriaweather.ca/clouds.php?image=fogHomework Assignment• Handout available today• Also posted on web page for class http://www.wou.edu/~brownkgo to ES 106 page and look for today’s date (April 9)• Due in one week, April 16– If you won’t be here that day, get it in early or have someone else bring it– If you weren’t here April 9, it is STILL DUE on April
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