Heat and energy transferEfhhfEnergy of phase change of waterwaterWater cycleyGroundwaterclick here for 9/page to printHeatHeat• Calorie–Amount of heat required to raise the qtemperature of 1 gram of pure water 1oC–Food‘Calories’are kilocaloriesFood Calories are kilocalories• Joule ~ ¼ of calorie–1 cal. = 4.184 JSpecific Heat CapacitySpecific Heat Capacity• Quantity of heat needed to change the temperature of given amount of a pgsubstance 1oC•Watervery high specific heat capacity•Water—very high specific heat capacity– 1 calorie raises one gram of water 1°C– 1 calorie raises one gram of rock ~5oC–Maritime areas more mild temperature thanMaritime areas more mild temperature than continental areasLaws of ThermodynamicsLaws of Thermodynamics1.Conservation of energy and matter1.Conservation of energy and matter2. Entropy is increased with conversion3. No system can reach absolute zeroC.P. Snow, the British scientist and author has offered up pan easy and funny way to remember the Three Laws. He says they can be translated as: (1) You cannot win (you can’t get something for nothing because matter and energy are conserved. (2)Ytbk( tttth(2)You cannot break even (you cannot return to the same energy state because entropy always increases(3)You cannot get out of the game (because absolute(3)You cannot get out of the game (because absolute zero is not attainable).Heat ExpansionHeat Expansion• Random motion causes substance to be bibigger•Liquids usually have greater heatLiquids usually have greater heat expansion than solidsTh t t diff t i f•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 ExpansionWater Expansion• Unusual response to coolingg• Contracts until reaching 4oCreaching 4oC • Expands slightly upon further cooling to 0oC•Expands 9% upon•Expands 9% upon freezingWater Molecule• Bent Pl•PolarWater ExpansionWater Expansion• Molecule shape fit together closer in liquid•Open structured crystal due to hydrogenOpen structured crystal due to hydrogen bonding of polar molecules upon freezingHeat Transfer: conductionHeat Transfer: conduction• Tile is a better conductor of heat than the wood floorHeat Transfer: convectionHeat Transfer: convection• Currents from heater shown by shadowsyHeat Transfer: radiationHeat Transfer: radiation• Does not need material to transfer radiant energygy• Dark bodies absorb it better than lightcolored onesthan light-colored onesRadiant EnergyRadiant EnergyAll bj t it th l•All objects emit thermal energy– Visible light above ~500oC– Re-emit absorbed radiation at wavelength according to temperature • Good absorbers are good gemitters•Poor absorbers are poorPoor absorbers are poor emittersHeat TransferHeat Transfer• Conduction–Direct molecule interaction– Transferring energy to next moleculeCti•Convection– Movement of fluid: liquid or gas• RadiationThrough open space–Through open space– Electromagnetic radiationWater: Energy of Phase ChangeWater: Energy of Phase Change• Calorie: energy to change 1 g water 1 K or 1 oCgy g g• 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/freezing•Energy of melting/freezing¾80 calories per gram= 334 J/gEnergy of phase change for waterEnergy of phase change for waterhttp://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.htmlWater: Energy to melt iceWater: Energy to melt ice• Energy goes into breaking the bonds that are holding the molecules in fixed position with respect to one another.p• 80 calories per gram of ice that melts.• Temperature remains constant during this.Water Heat of FusionWater Heat of Fusion• Heat added to ice causes the phase changeg• No change in temperature until all the ice is meltedis melted.• Heat taken up by water upon melting• Heat released from water upon freezing80 l i f t th t•80 calories per gram of water that goes from frozen to liquid, or liquid to frozenWater Heat of VaporizationWater Heat of Vaporization• Heat taken up by water upon vaporizing•Heat added to water causes the phaseHeat added to water causes the phase change, no change in temperature until all the water is vaporizedthe water is vaporized.• Heat released from water upon condensing (sometimes described as the heat of condensation)the heat of condensation)• 540 calories per gram of water that goes f t li id li id tfrom vapor to liquid, or liquid to vaporInClass ActivityIn-Class ActivityHow much energy is transferred to the environment when one gram of steam atenvironment when one gram of steam at 100oC condenses to water at 100oC?EfitiddtiEnergy of vaporization and condensation =540 calories/gram of waterInClass ActivityIn-Class ActivityHow much energy is transferred to the environment when one gram of boilingenvironment when one gram of boiling water at 100oC cools to 0oC?Dfiiti f l i h t i dt hDefinition of calorie: heat required to change the temperature of 1 gram of water 1oCInClass ActivityIn-Class ActivityHow much energy is transferred to the ith fttenvironment when one gram of water at 0oC freezes to ice at 0oC?EfltidfiftEnergy of melting and freezing of water80 calories/gramInClass ActivityIn-Class ActivityHow much energy is transferred to theHow much energy is transferred to the environment when one gram of steam at 100oClt0oCdf tb i?C cools to 0oC and freezes to become ice?Heat is released in this processHeat is released in this process Condense 1 g from steam to liquid540 cal/g x 1 g=540 cal released for condensation540 cal/g x 1 g 540 cal released for condensation Δ100oC x 1 cal/g x 1 g = 100 cal released for cooling80cal/gx1g=80 J to freeze80 cal/g x 1 g 80 J to freezeTotal these to get 720 calories are releasedThree hfphases of waterwaterhttp://www.cdli.ca/CITE/glaciers.htmAtmosphereAtmosphere• Evaporation –Energy goes into airgy g– Cools remaining waterCd ti•Condensation– Energy goes from air to surface– Warms local environmentWater CycleWater Cycle• 86% of evaporation from sea surface•14% of atmospheric moisture from land as14% of atmospheric moisture from land as EVAPOTRANSPIRATION•78% of precipitation on sea surface8% o p ec p tat o o sea su ace• 22% of water precipitated falls on land
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