22 Physical Properties - Amazon S322物理性质-亚马逊S

Therearepitchersoficewaterandlemonadeonapicnictable.Howdoyouknowwhichliquidisineachpitcher?It’seasy!Lemonadeisyellowandhasatarttastethatishardtomiss.Ayellowcolorandatarttastearetwopropertiesoflemonade.Whataresomeexamplesofphysicalproperties?Aphysicalpropertyisanycharacteristicofamaterialthatcanbeobservedormeasuredwithoutchangingthecompositionofthesubstancesinthematerial.ExamplesofPhysicalPropertiesViscosity,conductivity,malleability,hardness,meltingpoint,boilingpoint,anddensityareexamplesofphysicalproperties.

ViscosityThetendencyofaliquidtokeepfromflowingiscalleditsviscosity.Thickliquids,suchascornsyrupandhoney,haveahighviscosity.Thinliquids,suchasvinegarandwater,havealowviscosity.ExamplesofPhysicalPropertiesConductivityAmaterial’sabilitytoallowheattoflowiscalledconductivity.Materialsthathaveahighconductivity,suchasmetals,arecalledconductors.Goodconductorsofheatareusuallyalsogoodconductorsofelectricity.ExamplesofPhysicalPropertiesMalleabilityTheabilityofasolidtobehammeredwithoutshatteringismalleability.Mostmetals,suchasgold,aremalleable.Anicecubeorpieceofglassbreaksintosmallpieceswhenstruckwithahammer.Solidsthatshatterwhenstruckarebrittle,notmalleable.ExamplesofPhysicalPropertiesHardnessOnematerialcanscratchanothermaterialifitisharderthantheothermaterial.Akitchenknifecanscratchacoppersheetbecausestainlesssteelisharderthancopper.Thematerialusedtosharpentheknifeblademustbeharderthanstainlesssteel.Diamondisthehardestknownmaterial.ExamplesofPhysicalPropertiesThisTlingitcarverisusinganadzetocarveacanoefromWesternredcedar.Redcedarisarelativelysoftwood.Theadzeishard.ExamplesofPhysicalPropertiesMeltingandBoilingPointsThetemperatureatwhichamaterialchangesstateisaphysicalproperty.Thetemperatureatwhichasubstancechangesfromsolidtoliquid(melts)isitsmeltingpoint.Thetemperatureatwhichasubstancechangesfromliquidtogas(boils)isitsboilingpoint.

ExamplesofPhysicalPropertiesMeltingandBoilingPointsWhichofthesesubstancesareliquidsatroomtemperature(20

C,or68

F)?Answer:ExamplesofPhysicalPropertiesMeltingandBoilingPointsWhichofthesesubstancesareliquidsatroomtemperature(20

C,or68

F)?Answer:octane,

water,and

aceticacidExamplesofPhysicalPropertiesDensityTheratioofthemassofasubstancetoitsvolumeisitsdensity.Densitycanbeusedtotestthepurityofasubstance.Silverhasadensityof10.5g/cm3.Acoinwithadensityof9.9g/cm3isnotmadefromsilver,oritcontainssubstancesinadditiontosilver.ExamplesofPhysicalPropertiesHowcanknowingthephysicalpropertiesofmatterbeuseful?

Physicalpropertiesareusedtoidentifyamaterial,tochooseamaterialforaspecificpurpose,ortoseparatethesubstancesinamixture.

UsingPhysicalPropertiesUsingPropertiestoIdentifyMaterialsAmaterialcanbeidentifiedbyitsproperties.Decidewhichpropertiestotest.Dotestsonasampleoftheunknownmaterial.Comparetheresultswiththedatareportedforknownmaterials.UsingPhysicalPropertiesUsingPropertiestoChooseMaterialsPropertiesdeterminewhichmaterialsarechosenforwhichuses.Forexample,shoelacesmustbeflexible,thatistheymustbeabletobendwithoutbreaking.Theymustalsobedurable,thatis,theymustbeabletowithstandrepeateduse.UsingPhysicalPropertiesLacesinhikingbootsareusuallymadeofnylonorleather,notfromwood.UsingPhysicalPropertiesWhatprocessesareusedtoseparatemixtures?

Filtrationanddistillationaretwocommonseparationmethods.UsingPropertiestoSeparateMixturesFiltrationYoucanseparatehotteafromloosetealeavesbypouringthemixturethroughastrainer.Filtrationisaprocessthatseparatesmaterialsbasedonthesizeoftheirparticles.UsingPropertiestoSeparateMixturesThesestudentsfilter(sift)dirtthroughawirescreentolocatesmallobjects.Particlesofdirtaresmallenoughtopassthroughtheholes,butobjectssuchasbrokenbitsofpotteryaretoolarge.UsingPropertiestoSeparateMixturesDistillationSometimesalltheparticlesinasolutionaresmallenoughtopassthroughafilter.Distillationisaprocessthatseparatesthesubstancesinasolutionbasedontheirboilingpoints.UsingPropertiestoSeparateMixturesThechangeofwaterfromaliquidtoagasduringboilingisaphysicalchange.Aphysicalchangeoccurswhensomeofthepropertiesofamaterialchange,butthesubstancesinthematerialremainthesame.RecognizingPhysicalChangesDuringaphysicalchange,thesizeandshapeofamaterialcanchangebutnotthecomposition.SomeexamplesincludemeltingbutterinapancrumplingapieceofpaperslicingatomatoRecognizingPhysicalChangesSomebutnotallphysicalchangescanbereversed.Braidinghairisareversiblechange.Cuttinghaircannotbereversed.RecognizingPhysicalChangesAssessmentQuestionsWhichofthefollowingisnotaphysicalproperty?densityboilingpointflammabilityconductivity

AssessmentQuestionsWhichofthefollowingisnotaphysicalproperty?densityboilingpointflammabilityconductivity

ANS: CAssessmentQuestionsWhichofthesematerialsisnotmalleable?copperaluminumglassgold

AssessmentQuestionsWhichofthesematerialsisnotmalleable?copperaluminumglassgold

ANS: CAssessmentQuestionsInchoosingamaterialforuseasawiretocarryelectriccurrent,whichphysicalpropertywouldbemostimportant?conductivitymalleabilityhardnessboilingpoint

AssessmentQuestionsInchoosingamaterialforuseasawiretocarryelectriccurrent,whichphysicalpropertywouldbemostimportant?conductivitymalleabilityhardnessboilingpoint

ANS: AAssessmentQuestionsWhichofthesestatementsbestdescribesaphysicalchangeinapuresubstance?Thesubstancechangesintooneormorenewsubstances.Someofthepropertiesofthesubstancechange,butthematerialremainsthesame.Thepropertiesofthematerialdonotchange,andthematerialremainsthesame.Thesubstanceisseparatedintotwo