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1、DensityofMatterChemistry1215Experiment#3ObjectiveTherearetwoobjectivesforthisexperiment.Thefirstistousedensitymeasurementstodeterminethepercentcompositionofanunknownisopropylalcohol:watermixture.Thesecondobjectiveisusedensitytodeterminetheidentityofanunknownmetal.IntroductionDensityisaderivedquanti
2、tydefinedasmassdividedbyvolume(Equation1).Atanygiventemperature,thedensityofapuresubstanceisaconstantandisconsideredaphysicalpropertythatcanbeusedtoidentifythatsubstance.d=m/VEquation1TheSIunitsfordensityareg/mLforliquids,g/Lforgasses,andg/cm3forsolids.Becausethedensityofasubstanceisdependentontemp
3、erature,densitiesareusuallyreportedataspecifictemperature.Thedensityofapuresubstanceinitssolidstateisusuallygreaterthanitsdensityinaliquidstate.Waterisanexceptiontothisrule.Liquidwaterhasamaximumdensityof1.000g/mLat3.8oC.Ontheotherhand,solidwater,ice,hasadensityof0.9168g/mL.Theresultisthaticefloats
4、inwater.Densitiesofsubstancesareusuallydeterminedindirectlybasedonthemassandthevolumeofthesubstance.Massisdeterminedbymeasurementonabalanceorscale.Analyticalbalancesusedfordensitymeasurementsareusuallyveryaccurateinstrumentsthatmeasuremassestothenearest0.0001g.Thevolumeofaliquidisdeterminedusingvol
5、umetricglasswaresuchasavolumetricpipet,agraduatedcylinder,orapycnometer.Measurementsmadewithvolumetricpipetsareusuallymoreaccurateandmoreprecisethanthosemadewithgraduatedcylinders.Thevolumeofregularlyshapedsolidobjectssuchasspheres,cylinders,andcubes,canbecalculatedmathematicallyfromtheirmeasureddi
6、mensions.Forexample,thevolumeofacylinderwitharadius,r,of5.00mm(0.500cm)andaheight,h,of20.0cmcanbecalculatedusingequation2.V=pr2h=p(0.500cm)2(20.0cm)=15.7cm3Equation2Measurementofthevolumeofanirregularlyshapedobjectrequiresmoreingenuity.ForthismeasurementwecanusewhathasbecomeknownastheArchimedesprin
7、ciple(namedaftertheGreekphilosopher,ArchimedesofSyracuse).Forourpurposes,Archimedes’principlesimplystatesthatthevolumeofasolidobjectimmersedinaliquidisequaltothevolumeofliquiditdisplaced.ThelimitationofArch
