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1、What'sDistilling?(DevelopedwiththeassistanceofDr.PaigeStevenson,VirginiaTech)IntroductionYouhaveprobablyheardthetermdistillationanddistilledmanytimesduringyourlife.Forexample,youcanbuydistilledwateratthegrocerystore.Crudeoilisseparatedintoitsmanycomponents(methane,propane,butane,gasoline,ker
2、osene,oil,paraffinwax,andmajorcomponentsoftar/asphalt)bydistillation.Thetermdistillationreferstoatechniqueusedtoseparateoneormorevolatilecomponentsinaliquid/liquidorliquid/solidmixturebytakingadvantageofthedifferentvaporpressures(orboilingpoints)ofthecomponentsinthemixture.(Asubstancethatexh
3、ibitsasignificantvaporpressureatagiventemperatureiscalledvolatile.Tosmellasubstance,itmustbevolatilebecausesomeofitmustbeinthevaporphase.)Inthefirstexampleabove,distilledwateriswaterthathasbeenboiled(vaporized)andthencooledandcondensedintoanothervessel.Becausetheothersubstancesintheimpurewat
4、ertendtobenon-volatile(e.g.salts,bacteria),theyremainbehind,givingpurewater.Crudeoilcontainsmanyvolatilesubstances,makingitsdistillationmuchmorecomplex.Crudeoilisseparatedbyatechniquecalledfractionaldistillation.Whenyouhavemorethanonevolatilesubstance,bothsubstanceshaveasignificantvaporpress
5、ureattheboilingpointofthemorevolatile(lowerboiling)substance.Thegasmixturebeingcondensedthereforecontainsbothsubstances,butthelowerboilingsubstanceisinhigherconcentrationthanthehigherboilingsubstance.Toisolateapuresubstancefromthemixture,multipledistillationsmustbecompletedinsequence.Fractio
6、naldistillationallowsyoutoperformabunchof“mini-distillations”inoneset-up,ultimatelyyieldingbetterseparation.Whenperformingasimpleorfractionaldistillationtoseparatevolatilecomponentsofamixture,thedistilledliquidistypicallycollectedinsmallincrementscalled"fractions."Eachindividualfractionisthe
7、ntestedforpurityandcombinedwithotherpurefractionsorredistilled(ifnotpure)toeventuallyseparatethecomponentsofamixture.Goals:Inthislab,studentswill:1.comparetwodifferentdistillationset-ups(simpleandfractional)forseparatingmixtures.2.usethedistillatio
