Definition
Whenthesystem'stemperature,pressure,volume,stateofmatter,amountofmatter,phase,variousenergies,etc.areconstant,wesaythatthesystemisinastate(state).
Whenthesystemchangesfromonestate(initialstate)toanotherstate(finalstate),wesay:aprocesshasoccurred.Theprocessinwhichthetemperaturesoftheinitialstateandthefinalstateareequaliscalledanisothermalprocess.Theprocessinwhichthepressuresoftheinitialstateandthefinalstateareequaliscalledanequalpressureprocess.Theprocessinwhichthevolumeoftheinitialstateandthefinalstateareequaliscalledanisovolumetricprocess.
Idealizationisanimportantscientificmethod.Whenstudyingactualgases,idealgasescanbeused.Thestudyofmechanicscanalsorelyonanidealprocesswithoutfriction.Thermodynamicsalsoassumesanidealprocess,calledareversibleprocess.Areversibleprocessisaprocessthatapproachestheequilibriumstateinfinitely.Thereversibilitymentionedhereisnotaprocessofbothforwardandreverse,whichiscommonlyunderstood,butfromtheinitialstatetothefinalstate,andthenfromthefinalstatetotheinitialstate,acycle,whichisgoodforthesystemandtheenvironment,withoutleavingbehindAny"trace".Whatis"trace"?Thisisexactlywhatwewanttofigureout,anditwillbeexplainedslowlybelow.Wejustwanttosayherethatthisthermodynamicallyreversibleprocessisanidealprocess,justastheactualgasisnotanidealgas,andjustastheactualprocessofdoingmechanicalworkdoesnothaveanyfrictionanddoesnotexist,thedischargeoftheprimarybatteryisimpossible.Littleelectricenergyisnottransformedintothermalenergy,etc.,like"idealization".Allactualprocessesareirreversibleprocesses.Theidealthermodynamicallyreversibleprocessdoesnotexist,butitisalimitprocess,whichisextremelymeaningfulfordiscussingthermodynamics.
Therearetwoidealprocessesinthermodynamics,oneisthereversibleexpansionofanidealgas,andtheotheristhereversibledischargeofthegalvanicbattery.Theyarebothidealprocessesandcannotreallyexist,buttheworktheydoTheyarethelimitvalues​​ofexpansionworkandusefulwork.Theworkdoneinallactualprocessescannotreachorexceedtheworkdoneinthereversibleprocessnumerically.
Stateofmatter
Solid
Liquid
Gaseous
Plasma
Boaicondensedmatter
Fermioncondensedmatter
Neutronstate
Superconductingstate
Superfluidstate
Supersolidstate
Spontaneousprocessandnon-spontaneousprocess
Thermodynamicsalsodividestheprocessintospontaneousandnon-spontaneousprocesses.Spontaneousprocessesareprocessesthatoccurnaturallyinnature,andgowiththeflow;non-spontaneousprocessesareprocessesthatdonotoccurnaturally.Examplesareasfollows:
Heatflowsfromhightemperaturetolowtemperature
Waterflowsfromhighmountainstoplains
Windflowsfromhighpressuretolowpressure
Currentflowsfromhighpotential(positive)tolowpotential(negative)
Hydroxideunderpressureiscombinedintowaterandheatflowsfromlowtemperaturetohightemperature(refrigerator)
Waterflowsfromplaintomountain(pumper)
Airflowflowsfromlowpressuretohighpressure(compressor)
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Currentflowsfromlowelectricpotentialtohighelectricpotential(batterycharging)
Thedecompositionofwaterintohydrogenandoxygen(electrolysis)atnormaltemperatureandpressure
ThethermodynamicsprovethatinaclosedsystemIfaspontaneousprocessoccursintheprocess,thesystemmusthavethepossibilityofdoingusefulworktotheenvironment.Conversely,ifusefulworkmustbedonetoaclosedsystem,aprocesswilloccurinthesystem,andthisprocessmustbeanon-spontaneousprocess.