Brownian tsab ntawv tsa suab: ib tug txheej txheem cej luam.

Nyob rau hauv thaum ntxov ua sawv ntawm txoj kev loj hlob ntawm cov kev tshawb xav ntawm colloidal systems, nws txawm xav hais tias molecular kinetic zog cim kom muaj tseeb ntsiab. Long-term kev tshawb fawb tau qhia tias cov zog yog xam qhovkev thiab colloidal kev daws teeb meem. Nws yog pom tias ntawm lawv muaj tsis muaj qhov zoo sib txawv, thiab muaj tsuas yog ntau, uas nyob ntawm seb tsuas yog nyob rau qhov luaj li cas thiab zoo ntawm lub colloid hais (micelles). Yog li ntawd, cov lus qhib ntawm lub Brownian tsab ntawv tsa suab nyob rau hauv qhov kev txiav txim yog ntawm kuj zoo kawg tseem ceeb.

Rau cov thawj lub sij hawm (nyob rau hauv 1827), Brownian tsab ntawv tsa suab twb kawm los ntawm lus Askiv botanist Robert Brown. Yuav kom peb coj ib tug ultramicroscope rau paj ntoos nroj tsuag, tshem tawm nyob rau hauv ib tug nco dej, tus paub txog pom tias me me hais ntawm pollen irregularly (across) thiab tsis tu ncua txav mus li. Brownian tsab ntawv tsa suab - ib tug puas ntsoog, chaotic los yog zigzag suab ntawm microparticles. Heev heev cov kev tshawb fawb tau tsim hais tias tus random zog ntawm molecules yog tshwm sim los ntawm particle loj, me, kub thiab viscosity ntawm lub dispersion nruab nrab. Nyob rau hauv cov ntaub ntawv no, qhov xwm ntawm tus tshuaj muaj zoo tsis ntxim rau lawv lub zog.

Brownian tsab ntawv tsa suab thiab niaj hnub molecular-kinetic kev tshawb xav ntawm kua

Frankel tswv yim hais tias lub xaav ntawm ib tug qauv rearrangement nyob ze, txhua tus uas nyhav nyob nws thawj txoj hauj lwm, uas yog lub feem ntau ib qho kev zoo nyob rau hauv cov nqe lus ntawm lub zog.

Raws li ib tug tshwm sim, ceev thiab tas mus li lub zog ntawm nws tus kheej-diffusion txheej txheem ntawm molecules tshwm sim. Yaj nyob rau hauv ib cov kua microparticles (dispersion theem) ua ib tug zog kwv yees li tib yam li cov kuab molecule (dispersion nruab nrab). Vim tus nruam chaotic tsab ntawv tsa suab lawv tsiv mus nyob nquag thiab tsis nyob twj ywm nyob rau hauv tej qhov chaw.

Brownian suab ntawm tus hais thiab colloidal ncua tshwm sim vim thermal tsab ntawv tsa suab ntawm qhov nruab nrab lwm tus lub hais thiab lawv chaotic yeej ntawm no molecule. Raws li ib tug ntawm xws li tawm tsam microparticles across tsiv nyob rau hauv qhov chaw (disperse nruab nrab). Cov taw yog lub txiaj ntsim ntawm kev poob siab kev txiav txim rau ib tug tej lub sij hawm ntawm txoj kev tshawb (ib ob txog molecule yuav undergo mus txog 1020 tus cwj nrag). Muab lub fact tias lub me me luaj li cas ntawm cov molecule yog cov sib txawv ntawm cov punches los ntawm ces kaum sib txawv, lawv yuav mus nyob rau hauv txawv kev qhia. Nrog ib lub cheeb ntawm ntau tshaj tsib micrometres ntawm microparticles Brownian tsab ntawv tsa suab yog suab tsis cai. Ua qhov luaj li cas thiab molecular ceeb thawj los ntawm lawv absorbs poob siab. Yog li ntawd, hais nrog ib tug high school cov molecular ceeb thawj (mus txog tsib micrometers) ua xwb muab kev co.

Brownian tsab ntawv tsa suab thiab diffusion

Raws li ib tug tshwm sim ntawm lub Brownian thiab thermal tsab ntawv tsa suab ntawm molecules tshwm sim kawm tuab si lug concentration thoob plaws hauv lub tshuaj volume. Diffusion tau coj qhov chaw nyob rau hauv colloidal thiab txoj kev daws teeb meem.

Lub osmotic siab yog tshwm sim los ntawm lub xub ntiag ntawm micelles. Vim lub loj loj ntawm lub lwg me me thiab lawv me siab heev uas tsis muaj ntau. Ntawm cov hoob kawm, lub siab nyob rau hauv lub feem ntawm lub analyte colloidal tshuaj lom zem ntau yog nyob ntawm seb muaj cov impurities ntawm ntau yam electrolytes. Yog li, macromolecular kev daws teeb meem - polysaccharides, roj hmab, protein - ntawm 10-12 feem pua concentration muaj ib tug tseem ceeb osmotic siab. Tsaug rau qhov tshwj xeeb pab kiag li lawm (osmometry) tau txiav txim osmotic siab ntawm cov ntshav ntshav, uas yog nyob rau nruab nrab txog 25 hli Hg. Nws yog muaj pov thawj, uas lub siab yog ncaj qha xwm yeem mus rau concentration ntawm yaj tshuaj nyob rau hauv colloidal los yog muaj tseeb ntsiab.