Latent Heat - Definition, Types, Formula, Fusion ... - Byju's

Latent heat of vaporization is the heat consumed or discharged when matter disintegrates, changing state from fluid to gas state at a consistent temperature ... CheckoutJEEMAINS2022QuestionPaperAnalysis: CheckoutJEEMAINS2022QuestionPaperAnalysis: × DownloadNow JEEIITJEEStudyMaterialLatentHeat Previous Next LatentHeat Latentheatisdefinedastheheatorenergythatisabsorbedorreleasedduringaphasechangeofasubstance.Itcouldeitherbefromagastoaliquidorliquidtosolidandviceversa.Latentheatisrelatedtoaheatpropertycalledenthalpy. However,animportantpointthatweshouldconsiderregardinglatentheatisthatthetemperatureofthesubstanceremainsconstant.Asfarasthemechanismisconcerned,latentheatistheworkthatisneededtoovercometheattractiveforcesthatholdmoleculesandatomstogetherinasubstance. Let’stakeanexample.Supposeasolidsubstanceischangingtoaliquid,itneedstoabsorbenergytopushthemoleculesintoawider,morefluidvolume.Similarly,whenasubstancechangesfromagasphasetoaliquid,theirdensitylevelsalsoneedtogofromlowertoahigherlevelwhereinthesubstancethenneedstoreleaseorloseenergysothatthemoleculescomeclosertogether.Inessence,thisenergythatisrequiredbyasubstancetoeitherfreeze,meltorboilissaidtobelatentheat. EarlyDevelopmentsoftheConcept EnglishscientificexpertJosephBlackpresentedtheideaoflatentheatsomewhereclosetothelongperiodsof1750and1762.ScotchbourbonproducershademployedBlacktodecidethebestblendoffuelandwaterforrefiningandtoexaminechangesinvolumeandweightatasteadytemperature.Darkappliedcalorimetryforhisinvestigationandrecordedlatentheatesteems. EnglishphysicistJamesPrescottJouleportrayedlatentheatasatypeofpotentialvitality.Jouleacceptedthevitalityrelieduponthespecificdesignofparticlesinasubstance.Actually,itisthedirectionofparticlesinsideanatom,theirsubstanceholding,andtheirextremitythatinfluencelatentheat. TypesofLatentHeatTransfer Letsusdiscusssomethedifferenttypesoflatentheatthatcanoccur. LatentHeatofFusion Latentheatoffusionistheheatconsumedordischargedwhenmattermelts,changingstagefromsolidtofluid-structureataconsistenttemperature. The‘enthalpy’offusionisalatentheat,inlightofthefactthatduringsofteningtheheatenergyexpectedtochangethesubstancefromsolidtofluidatairpressureisthelatentheatoffusion,asthetemperaturestayssteadyduringtheprocedure.Thelatentheatoffusionistheenthalpychangeofanymeasureofsubstancewhenitdissolves. Atthepointwhentheheatoffusionisreferencedtoaunitofmass,itistypicallycalledthespecificheatoffusion,whilethemolarheatoffusionalludestotheenthalpychangepermeasureofsubstanceinmoles. Thefluidstatehashigherinwardenergythanthesolid-state.Thisimpliesenergymustbeprovidedtothesolidsoastodissolveitandenergyisdischargedfromafluidwhenitsolidifies,onthegroundsthattheparticlesinthefluidexperiencemorefragileintermolecularforcethushavehigherpotentialenergy(asortofbond-separationenergyforintermolecularpowers). Atthepointwhenfluidwateriscooled,itstemperaturefallsrelentlesslyuntilitdropsjustunderneaththelineofthepointofsolidificationat0°C.Thetemperatureatthatpointstaysconsistentatthepointofsolidificationwhilethewatertakesshape.Whenthewateristotallysolidified,itstemperaturekeepsonfalling. Theenthalpyoffusionisquiteoftenapositiveamount;heliumisthemainknownexception.Helium-3hasanegativeenthalpyoffusionattemperaturesbeneath0.3K.Helium-4additionallyhasamarginallynegativeenthalpyoffusionunderneath0.77K(−272.380°C).Thisimplies,atsuitablesteadyweights,thesesubstancessolidifywiththeexpansionofheat.[2]Forthesituationof4He,thisweightterritoryissomewhereintherangeof24.992and25.00atm(2,533kPa). LatentHeatofVaporization Latentheatofvaporizationistheheatconsumedordischargedwhenmatterdisintegrates,changingstatefromfluidtogasstateataconsistenttemperature. Theheatofvaporizationofwateristhemostelevatedknown.Theheatofvaporizationischaracterizedasthemeasureofheatexpectedtotransform1gofafluidintoafume,withoutachangeinthetemperatureofthefluid.Thistermisn’tintherundownofdefinitionsgivenbyWeast(1964),sothedefinitionoriginatesfromWebster’sNewWorldDictionaryoftheAmericanLanguage(1959).Theunitsarecal/gram.Theheatofvaporizationislatentheat.LatentoriginatesfromtheLatinwordlatere,whichintendstoliecovereduporhid.Latentheatistheextraheatrequiredtochangetheconditionofasubstancefromsolidtofluidatitssofteningpoint,orfromfluidtogasatitsbreakingpointafterthetemperatureofthesubstancehascometobothofthesefocuses. Notethatlatentheatisrelatedwithnoadjustmentintemperature,yetadifferenceinthestate.Asaresultofthehighheatofvaporization,thevanishingofwaterhasanarticulatedcoolingimpactandbuilduphasawarmingimpact. Similartothecasefor‘HeatofFusion/Melting,’theheatofvaporization/buildupadditionallyspeakstothemeasureofheattradedduringastagemove.Forvaporization,itistheamountofheat(540calg−1)expectedtochangeover1gofwaterto1gofwaterfume.Asimilarmeasureofheatistradedordischargedinthestagemoveduringthebuildupof1gwaterfumeto1gofwater. Amphibianresearchersmightbenormallyintriguedwiththeenormousmeasureofheattraded(80calg−1)inthestagemovefromwatertoice,orfromicetowater,yetthemeasureofheattraded(540calg−1)inthestagemovefromwatertowaterfume,orwaterfumetowateris6.75timesbigger(540/80=6.75).Despitethefactthatthesignificanceofthisenormousmeasureofheattradethroughvaporizationorbuildupmightbeundervaluedbypeople,itisimmense.Onalittleyetbasicscaleforever,waterdissipatingoffsweatingwarm-bloodedcreatures,includingpeople,keepsupinternalheatlevelsinsidethinsurvivablepointsofconfinement.Onaworldwidescale,theapparentlyperpetualstagemovesbetweenfluidwaterandwaterfumeintheclimatearekeydeterminantsintheredistributionofwaterandheatinsidethehydrologicalcyclefarandwide. Theenthalpyofvaporization,ΔHv,isadditionallynamedthe“latentheatofvaporization.”AndΔHvisthedistinctionbetweentheenthalpyofthesoakedfumeandthatoftheimmersedfluidatasimilartemperature.Theenthalpyofvaporizationinformationisutilizedinprocessestimations,forexample,theplanofalleviationframeworksincludingunpredictablemixes.Inrefining,theheatofvaporizationesteemsareexpectedtodiscovertheheatloadsforthereboilerandcondenser,andinformationontheenthalpyofvaporizationisrequiredinthestructureofheatexchangersfordisintegratingfluids. ReasonableHeat Althoughreasonableheatisfrequentlycalledlatentheat,itisanythingbutasteadytemperaturecircumstance,norisastagechangeincluded.Reasonableheatreflectsheatmoveamonganitemandtheirenvironment.Theheatcanbe“detected”asanadjustmentinanitem’stemperature. ReasonableHeatandMeteorology Whilelatentheatofcombinationandvaporizationareutilizedinmaterialscienceandscience,meteorologistslikewisethinkaboutreasonableheat.Atthepointwhenlatentheatisingestedordischarged,itproducesinsecurityintheclimate,conceivablydeliveringextremeclimate.Thechangeinlatentheatadjuststhetemperatureintocontactwithhotterorcoolerair.Bothlatentandreasonableheatcauseairtomove,creatingwindandverticalmovementofairmasses. InstancesofLatentandSensibleHeat Everydaylifeisloadedupwithinstancesoflatentandreasonableheat: Bubblingwateronastovehappenswhenwarmvitalityfromtheheatingcomponentismovedtothepotandthustothewater.Atthepointwhenenoughvitalityisprovided,fluidwatergrowstofromwaterfumeandthewaterbubbles.Agiganticmeasureofvitalityisdischargedwhenwaterbubblesareformed.Sincewaterhassuchahighheatofvaporization,it’sanythingbutdifficulttogetscorchedbysteam. Correspondingly,significantenergymustbeassimilatedtochangeoverfluidwatertoiceinacooler.Thecoolerexpelsheatenergyforpermittingthestageprogresstohappen.Waterhasahighlatentheatofcombination,sotransformingwaterintoicerequiresexpulsionofmoreenergythansolidifyingfluidoxygenintosolidoxygen,perunitgram. SpecificLatentHeat Specificlatentheatischaracterizedasthemeasureofheatenergy(heat,Q)thatisconsumedordischargedwhenabodyexperiencesasteadytemperatureprocess. Theformulaforspecificlatentheatis: L=Q/m Where: Listhespecificlatentheat Qistheheatretainedordischarged misthemassofasubstance Themostwidelyrecognizedkindsofconsistenttemperatureformsarestagechanges,forexample,liquefying,solidifying,vaporization,orbuildup.Theenergyisviewedas“latent”onthegroundsthatitisbasicallycoveredupinsidetheatomsuntilthestagechangehappens.Themostwell-knownunitsofspecificlatentheatarejoulespergram(J/g)andkilojoulesperkilogram(kJ/kg). Specificlatentheatisanescalatedpropertyofissue. FrequentlyAskedQuestionsonLatentHeatWhatarethetypesoflatentheattransfer? Thetwoformsoflatentheatarelatentheatoffusion(melting)andlatentheatofvapourisation(boiling). Whatisspecificlatentheat? Thespecificlatentheatistheamountofenergyrequiredtochangethestateof1kgofthesubstancewithoutchangingthetemperatureofthesubstance. Whatisanexampleoflatentheat? Thetemperatureoftheboilingwaterremains1000Ctillthelastdropevaporates. Canlatentheatbemeasuredusingathermometer? Athermometercannotmeasurelatentheat. TestyourKnowledgeonLatentheat Q5 PutyourunderstandingofthisconcepttotestbyansweringafewMCQs.Click‘StartQuiz’tobegin! Selectthecorrectanswerandclickonthe“Finish”buttonCheckyourscoreandanswersattheendofthequiz StartQuiz Congrats! 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