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ID:33159309
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页数:4页
时间:2019-02-21
《spontaneous processes自发过程》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、SpontaneousProcesses•Aspontaneousprocessisonethatdoesoccurunderthegivensetofconditions.•Ifareactiondoesnotoccurunderagivensetofconditions,itissaidtobenon-spontaneous.SpontaneousProcessesSometypesofspontaneousprocesses:Phasetransitions(melting,freezing)Mixinganddissol
2、vingofsolutesintosolutionExpansionofgasesintoanevacuatedbulbHeattransferfromhottocoldobjectsMovementtowardschemicalequilibriumEverydayExamples:•Waterfreezesspontaneouslybelow0oCandmeltsspontaneouslyabove0oC@1atm•Alumpofsugarspontaneouslydissolvesinacupofcoffee,butdis
3、solvedsugardoesnotspontaneouslyreappearinitsoriginalform•Expansionofagasinanevacuatedbulbisaspontaneousprocess.Thegatheringofallgasmoleculesintoonelocationisnotspontaneous•Heatflowfromahotterobjecttoacolderoneisspontaneous,butthereverseneverhappensspontaneously•Irone
4、xposedtowaterandoxygenformsrust,butrustdoesnotspontaneouslychangetoironSpontaneousProcessWhatmakesaprocessspontaneous?•Often,butnotalways,asystemthatisspontaneoustriestominimizeitsenergy.•AspontaneoussystemalwaysmaximizesitsENTROPY.Entropy(S)•Entropy(S)isadirectmeasu
5、reoftherandomnessordisorderofasystem•Atdisorderincreases,Entropyincreases•EntropycanalsoberelatedtoprobabilityOrderofEntropy(S)•Forallsubstances,theparticlesinthesolidstatearemoreorderedthanthoseintheliquidstate,whicharebothmoreorderedthanthoseinthegaseousstate.Ssoli
6、d0)Entropy
7、asastatefunction•Likeenergyandenthalpy,entropyisastatefunction.∆S=Sf–Si•Ifthechangeresultsinanincreaseinrandomness,thenSf>Si•Statefunctionsarepropertiesthataredeterminedbythestateofthesystem.SecondLawofThermodynamics•Theentropyoftheuniverseincreasesinaspontaneousproc
8、essandremainsunchangedinandequilibriumprocess.Spontaneous:∆Suniv=∆Ssys+∆Ssurr>0Equilibrium:∆Suniv=∆Ssys+∆Ssurr=0EntropyChangesinthe
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