Latent heat - Energy Education

The latent heat of vaporization is the thermal energy required for a liquid to vaporize to a gas or the amount that is released when a gas condenses to a ... English Français Español EnergyEducation Navigationmenu ENERGYSOURCES Fuels FossilFuels Biofuels NuclearFuels Flows Hydro Solar Wind Geothermal ENERGYUSE Carriers Electricity Gasoline Hydrogen Sectors Transportation Residential Industrial ENERGYIMPACTS Livingstandard Pollution AcidRain Smog Pollutants ClimateChange ClimateFeedback OceanAcidification RisingSeaLevel Search Latentheat Latentheatistheheatrequiredforanobjecttochangephase(melt,boil,freeze,etc.).Thisenergyiscloselyrelatedtoenthalpy.[1]Infigure1,verycoldicehasheataddedtoit.Thetemperaturegoesup,sothat'ssensibleheat,butonceitstartsmelting,thatheatislatentheat(andisrepresentedbytheflatpartsoftheline,duringmeltingorevaporation). Figure1.Addingheattowatercaneitherraisethetemperatureorchangethephase.[2]Theheatthatchangesthetemperatureissensibleheat,theheatthatchangesthephaseislatentheat. Fusion Thelatentheatoffusionistheheatrequiredforanobjecttogofromthesolidstatetotheliquidstate,orviceversa.[1]Sinceitsvalueisgenerallymuchhigherthanspecificheat,itallowsyoutokeepabeveragecoldformuchlongerbyaddingicethansimplyhavingacoldliquidtobeginwith.It'salsowhyfrozenmeattakesalongtimetothaw,butonceitsthawed,itheatsupquickly.Thelatentheatoffusionisalsoreferredtoastheenthalpyoffusion. Iceandwaterhaveenormouslatentheatsassociatedwiththemwhichiswhysnowtakessolongtomeltandboilingwaterisusedforcooking.Thisisalsoimportantinkeepingourplanetcomfortabletoliveon,andprovidesafairamountofresistancetoclimatechange. Vaporization Thelatentheatofvaporizationisthethermalenergyrequiredforaliquidtovaporizetoagasortheamountthatisreleasedwhenagascondensestoaliquid.[1]Thelatentheatofvaporizationisalsoreferredtoastheenthalpyofvaporization.Waterhasahighlatentheatofvaporization,whichiswhysteamburnsaresodangerous.Whensteamburnsaperson'sarmforexample,thisenergytransfercausesthesteamtocondense—whichusesmuchmoreenergythansimplychangingthetemperature.Hotwaterwouldalsoburn,however,ifapersonweretogetahotwaterburn—thatwouldonlychangethetemperatureoftheperson'shandandthewater,andwillnotcauseaphasechange.Therefore,steamwaterburnsaremuchworse(becauseaphasechangeisactuallyhappening). SpecificLatentHeat Figure2:Specificlatentheatoffusion,vaporizationandsublimation.[3] Thespecificlatentheatofasubstanceistheamountofenergyneededtochangethestateof1kgofthesubstancewithoutchangingitstemperature.[4]Thedistinctionfromlatentheatisduetotheterm"specific,"whichtellsusthatthesubstanceisbeingmeasuredperunitmass.Inaddition,sincespecificlatentheatismeasuredperunitmass,itisanintensivepropertyofmatter. Thespecificlatentheat(representedbythesymbol[math]L[/math])ofamaterialisameasureoftheheatenergy([math]Q[/math])perunitmass([math]m[/math])releasedorabsorbedduringaphasechange.Specificlatentheatcanbefoundusingtheformula[math]Q=mL[/math].Rearrangingtheformulaweget: [math]L=\frac{Q}{m}[/math] where: [math]L[/math]isthespecificlatentheatforaparticularsubstance,eitherLfforfusion,orLvforvaporization. [math]Q[/math]isthethermalenergyreleasedorabsorbedduringthephasechangeofthesubstance(usuallyinkJ). [math]m[/math]isthemassofthesubstance(usuallyinkg). Tolearnmoreaboutenthalpyandlatentheatpleaseseehyperphysics. ForFurtherReading Solid,Liquid,Gas Steam Enthalpyofvaporization,Enthalpyoffusion Specificheatcapacity Climatechange Orexplorearandompage References ↑1.01.11.2RandallKnight,PhysicsforScientistsandEngineers,3rdEd.NewYork:Pearson,2013,Ch.17,p.482. ↑WikimediaCommons[Online],Available:https://commons.wikimedia.org/wiki/File:Water_Phase_Change_Diagram.png#/media/File:Water_Phase_Change_Diagram.png ↑"Latentheat",CambridgeUniversityPress,2014.[Online].Available:https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20190207075706603-0570:9781107326200:61588figu30.png?pub-status=live.[Accessed:06-May-2021]. ↑Specificlatentheat,BBCBitesize,2021.[Online].Available:https://www.bbc.co.uk/bitesize/guides/zg6bdxs/revision/4.[Accessed:06-May-2021]. Retrievedfrom"https://energyeducation.ca/wiki/index.php?title=Latent_heat&oldid=10346" Contactus Aboutus Privacypolicy Termsofuse