Ib ntu tseem ceeb ntawm thermodynamics yog kev kawm txog kev hloov pauv ntawm cov theem sib txawv ntawm cov khoom, txij li cov txheej txheem no tshwm sim hauv kev coj ua thiab yog qhov tseem ceeb rau kev kwv yees tus cwj pwm ntawm lub cev hauv qee yam xwm txheej. Cov kev hloov pauv no yog hu ua theem kev hloov pauv, uas tsab xov xwm tau mob siab rau.
Lub tswvyim ntawm ib theem thiab qhov system tivthaiv
Ua ntej yuav mus rau kev txiav txim siab ntawm theem kev hloov pauv hauv physics, nws yuav tsum tau txhais lub tswvyim ntawm theem nws tus kheej. Raws li paub los ntawm cov chav kawm ntawm physics dav dav, muaj peb lub xeev ntawm cov teeb meem: gaseous, khoom thiab kua. Hauv ntu tshwj xeeb ntawm kev tshawb fawb - hauv thermodynamics - cov kev cai lij choj raug tsim los rau cov theem ntawm cov teeb meem, thiab tsis yog rau lawv lub xeev ntawm kev sib sau. Ib theem yog to taub raws li ib tug tej yam ntim ntawm cov teeb meem uas muaj ib tug homogeneous qauv, yog yus muaj los ntawm ib tug tshwj xeeb lub cev thiab tshuaj zog thiab yog cais los ntawm tag nrho cov teeb meem los ntawm ciam teb, uas yog hu ua interphase.
Yog li, lub tswv yim ntawm "theem" nqa ntau cov ntaub ntawv tseem ceeb ntawm cov khoom.tseem ceeb tshaj nws lub xeev ntawm aggregation. Piv txwv li, cov khoom hauv lub xeev ntawm cov hlau xws li hlau tuaj yeem ua tau raws li cov theem hauv qab no: qhov kub thiab txias sib nqus lub cev-centered cubic (BCC), tsis kub-kub tsis-magnetic bcc, lub ntsej muag-centered cubic (fcc), thiab siab- kub tsis sib nqus bcc.
Ntxiv rau lub tswv yim ntawm "theem", cov kev cai ntawm thermodynamics kuj siv lo lus "cov khoom", uas txhais tau hais tias muaj pes tsawg leeg ntawm cov khoom siv tshuaj lom neeg uas tsim los ntawm cov txheej txheem tshwj xeeb. Qhov no txhais tau hais tias cov theem tuaj yeem yog monocomponent (1 chemical element) lossis multicomponent (ntau yam tshuaj).
Gibbs' theorem thiab qhov sib npaug ntawm theem ntawm lub cev
Yuav kom nkag siab txog theem kev hloov pauv, nws yog qhov tsim nyog kom paub qhov sib npaug ntawm lawv. Cov xwm txheej no tuaj yeem ua lej tau los ntawm kev daws qhov system ntawm Gibbs sib npaug rau txhua tus ntawm lawv, piv txwv tias lub xeev sib npaug tau mus txog thaum tag nrho Gibbs lub zog ntawm lub kaw lus cais tawm los ntawm sab nraud cuam tshuam tsis hloov.
Raws li kev daws teeb meem ntawm qhov sib npaug, cov xwm txheej tau txais rau qhov muaj kev sib npaug ntawm ob peb theem: ib qho kev sib cais yuav tsum tsis txhob hloov zuj zus thaum muaj kev kub ntxhov, tshuaj muaj peev xwm ntawm txhua yam thiab qhov kub thiab txias hauv txhua theem. sib npaug sib npaug.
Gibbs theem txoj cai rau kev sib npaug
Ib qho system uas muaj ob peb theem thiab cov khoom tuaj yeem ua kom sib npaug tsis yog xwbnyob rau hauv tej yam kev mob, piv txwv li, ntawm ib tug tshwj xeeb kub thiab siab. Qee qhov kev hloov pauv hauv Gibbs theorem rau qhov sib npaug tuaj yeem hloov pauv thaum tswj hwm tus lej ntawm theem thiab tus lej ntawm cov khoom sib npaug hauv qhov sib npaug. Tus naj npawb ntawm cov kev hloov pauv uas tuaj yeem hloov pauv yam tsis cuam tshuam qhov sib npaug hauv qhov system hu ua tus naj npawb ntawm kev ywj pheej ntawm qhov system no.
Tus naj npawb ntawm kev ywj pheej l ntawm lub kaw lus suav nrog f theem thiab k cov khoom yog txiav txim siab tshwj xeeb los ntawm Gibbs theem txoj cai. Txoj cai no yog sau ua lej raws li nram no: l + f=k + 2. Yuav ua li cas nrog txoj cai no? Yooj yim heev. Piv txwv li, nws paub tias lub kaw lus muaj f=3 equilibrium theem. Dab tsi yog qhov tsawg kawg nkaus ntawm cov khoom xws li qhov system tuaj yeem muaj? Koj tuaj yeem teb cov lus nug los ntawm kev xav raws li hauv qab no: nyob rau hauv cov ntaub ntawv ntawm qhov sib npaug, cov xwm txheej nruj tshaj plaws muaj nyob rau thaum nws pom tau hais tias tsuas yog ntawm qee qhov ntsuas, uas yog, kev hloov pauv ntawm cov ntsuas ntsuas kub yuav ua rau qhov tsis sib xws. Qhov no txhais tau tias tus naj npawb ntawm kev ywj pheej l=0. Hloov qhov paub qhov tseem ceeb ntawm l thiab f, peb tau txais k=1, uas yog, ib qho system uas peb theem nyob rau hauv equilibrium tuaj yeem muaj ib feem. Ib qho piv txwv tseem ceeb yog qhov peb npaug ntawm cov dej, qhov twg dej khov, dej ua kua, thiab chav nyob hauv qhov sib npaug ntawm qhov kub thiab txias.
Kev faib cov theem hloov pauv
Yog tias koj pib hloov qee qhov ntsuas ntsuas kub hauv qhov system hauv qhov sib npaug, koj tuaj yeem saib seb ib theem yuav ploj mus thiab lwm qhov yuav tshwm sim. Ib qho piv txwv yooj yim ntawm cov txheej txheem no yog cov dej khov yaj thaum nws rhuab.
Muab hais tias Gibbs sib npaug tsuas yog nyob ntawm ob qhov sib txawv (siab thiab kub), thiab theem kev hloov pauv cuam tshuam nrog kev hloov pauv ntawm cov kev hloov pauv no, tom qab ntawv lej kev hloov pauv ntawm theem tuaj yeem piav qhia los ntawm kev sib txawv ntawm Gibbs lub zog ntawm kev hwm rau nws. sib txawv. Nws yog txoj hauv kev no uas tau siv los ntawm Austrian physicist Paul Ehrenfest hauv xyoo 1933, thaum nws tau sau cov kev faib tawm ntawm txhua qhov kev paub txog cov txheej txheem thermodynamic uas tshwm sim nrog kev hloov pauv hauv theem sib npaug.
Los ntawm cov hauv paus ntsiab lus ntawm thermodynamics nws ua raws li cov thawj derivative ntawm Gibbs lub zog hais txog qhov kub thiab txias yog sib npaug rau qhov kev hloov pauv hauv entropy ntawm lub system. Lub derivative ntawm Gibbs lub zog hais txog lub siab yog sib npaug ntawm qhov kev hloov pauv hauv ntim. Yog hais tias, thaum cov theem hauv lub cev hloov pauv, qhov entropy lossis ntim tau tawg, uas yog, lawv hloov sai sai, ces lawv hais txog kev hloov pauv thawj zaug.
Ntxiv mus, qhov thib ob derivatives ntawm Gibbs lub zog hais txog qhov kub thiab txias yog lub peev xwm kub thiab cov coefficient ntawm volumetric expansion, feem. Yog hais tias qhov kev hloov pauv ntawm theem yog nrog los ntawm kev tsis sib txuas hauv qhov tseem ceeb ntawm cov khoom siv lub cev, ces ib tus hais txog kev hloov pauv thib ob.
Piv txwv ntawm kev hloov pauv ntawm theem
Muaj ntau qhov sib txawv ntawm qhov sib txawv. Nyob rau hauv lub moj khaum ntawm qhov kev faib tawm no, cov piv txwv zoo ntawm kev hloov ntawm thawj hom yog cov txheej txheem ntawm cov hlau melting los yog condensation ntawm dej vapor los ntawm huab cua, thaum muaj lub ntim dhia hauv qhov system.
Yog tias peb tham txog kev hloov pauv thib ob, tom qab ntawd cov piv txwv zoo yog qhov hloov pauv ntawm cov hlau los ntawm cov hlau nplaum mus rau lub xeev paramagnetic ntawm qhov kub thiab txias.768 ºC los yog kev hloov pauv ntawm tus neeg xyuas pib hlau mus rau hauv lub xeev superconducting ntawm qhov kub thiab txias zero kiag li.
Sib piv uas piav txog kev hloov pauv ntawm thawj hom
Hauv kev xyaum, feem ntau yuav tsum paub tias qhov kub, siab thiab nqus (tso tawm) lub zog hloov pauv li cas hauv lub cev thaum hloov pauv theem tshwm sim hauv nws. Ob qhov sib npaug tseem ceeb yog siv rau lub hom phiaj no. Lawv tau txais los ntawm kev paub txog cov hauv paus ntawm thermodynamics:
- Clapeyron cov mis, uas tsim kev sib raug zoo ntawm lub siab thiab qhov kub thiab txias thaum hloov pauv ntawm cov theem sib txawv.
- Clausius cov mis uas txuas cov nqus tau (tso tawm) lub zog thiab qhov kub ntawm lub cev thaum lub sijhawm hloov pauv.
Kev siv ntawm ob qhov sib npaug tsis yog tsuas yog kom tau txais kev sib npaug ntawm lub cev ntau, tab sis kuj tseem txiav txim siab txog qhov taw qhia ntawm txoj kab nqes ntawm qhov sib npaug ntawm cov duab kos.
Sib piv piav txog kev hloov pauv ntawm hom thib ob
Kev hloov pauv ntawm hom 1 thiab thib 2 tau piav qhia los ntawm qhov sib npaug sib txawv, txij li daim ntawv thov Clausius thiab Clausius equations rau kev hloov pauv thib ob ua rau kev ua lej tsis meej.
Los piav qhia txog qhov kawg, qhov sib npaug Ehrenfest tau siv, uas tsim kev sib raug zoo ntawm kev hloov pauv hauv siab thiab kub los ntawm kev paub txog kev hloov pauv ntawm lub peev xwm kub thiab coefficient ntawm volumetric expansion thaum lub sij hawm hloov pauv. Qhov sib npaug Ehrenfest yog siv los piav txog kev hloov pauv ntawm tus neeg xyuas pib-superconductor thaum tsis muaj qhov sib nqus.
Qhov tseem ceebPhase diagrams
Phase diagrams yog cov duab sawv cev ntawm thaj chaw uas cov theem sib thooj muaj nyob hauv qhov sib npaug. Cov cheeb tsam no tau sib cais los ntawm cov kab sib npaug ntawm cov theem. P-T (siab-temperature), T-V (kub-ntim), thiab P-V (siab-ntim) theem daim duab yog feem ntau siv.
Qhov tseem ceeb ntawm daim duab qhia theem nyob rau hauv qhov tseeb tias lawv tso cai rau koj los twv seb theem twg yuav nyob rau hauv thaum cov xwm txheej sab nraud hloov raws li. Cov ntaub ntawv no yog siv rau hauv kev kho cua sov ntawm ntau yam ntaub ntawv txhawm rau kom tau txais cov qauv uas xav tau.
