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1、CHAPTER1INTRODUCTION1.1Whatisthermodynamics?Thermodynamicsisthesciencewhichhasevolvedfromtheoriginalinvestiga-tionsinthe19thcenturyintothenatureofheat."Atthetime,theleadingtheoryofheatwasthatitwasatypeoffluid,whichcouldflowfromahotbodytoacolderonewhentheywe
2、rebroughtintocontact.Wenowknowthatwhatwasthencalledheat"isnotafluid,butisactuallyaformofenergy{itistheenergyassociatedwiththecontinual,randommotionoftheatomswhichcomposemacroscopicmatter,whichwecan'tseedirectly.Thistypeofenergy,whichwewillcallthermalenergy
3、,canbeconverted(atleastinpart)tootherformswhichwecanperceivedirectly(forexample,kinetic,gravitational,orelectricalenergy),andwhichcanbeusedtodousefulthingssuchaspropelanautomobileora747.Theprinciplesofthermodynamicsgoverntheconversionofthermalenergytoother
4、,moreusefulforms.Forexample,anautomobileenginecanbethoughofasadevicewhich rstconvertschemicalenergystoredinfuelandoxygenmoleculesintothermalen-ergybycombustion,andthenextractspartofthatthermalenergytoperformtheworknecessarytopropelthecarforward,overcomingf
5、riction.Thermody-namicsiscriticaltoallstepsinthisprocess(includingdeterminingthelevelofpollutantsemitted),andacarefulthermodynamicanalysisisrequiredforthedesignoffuel-ecient,low-pollutingautomobileengines.Ingeneral,thermody-namicsplaysavitalroleinthedesig
6、nofanyengineorpower-generatingplant,andthereforeagoodgroundinginthermodynamicsisrequiredformuchworkinengineering.Ifthermodynamicsonlygovernedthebehaviorofengines,itwouldprobablybethemosteconomicallyimportantofallsciences,butitismuchmorethanthat.Sincetheche
7、micalandphysicalstateofmatterdependsstronglyonhowmuchthermalenergyitcontains,thermodynamicprinciplesplayacentralroleinanydescriptionofthepropertiesofmatter.Forexample,thermodynamicsallowsustounderstandwhymatterappearsindi erentphases(solid,liquid,orgaseous
8、),andunderwhatconditionsonephasewilltransformtoanother.1CHAPTER1.INTRODUCTION2Thecompositionofachemically-reactingmixturewhichisgivenenoughtimetocometoequilibrium"isalsofullydeterminedbythermodynamicprincipl
