chapter 2 properties of matter - wikispaces：2章性能wikispaces物

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1、CHAPTER2:PROPERTIESOFMATTER2.1OBJECTIVESnStudentswillbeableto:¨Classifypuresubstancesaselementsorcompounds¨Describethecharacteristicsofanelement¨Describethecharacteristicsofacompound¨Distinguishpuresubstancesfrommixtures¨Classifymixturesas“hetero”or“homo”¨Classifymixturesassolution

2、s,suspensions,orcompounds.I.Whyareelementsandcompoundsclassifiedaspuresubstances?A.Apuresubstanceismatterthatalwayshasexactlythesamecomposition.1.Tablesaltandtablesugararetwoexamplesofpuresubstances.2.Substancescanbeclassifiedintotwocategories—elementsandcompounds.B.Everysampleofag

3、ivensubstancehasthesamepropertiesbecauseasubstancehasafixed,uniformcomposition.II.Howdomixturesdifferfrompuresubstances?A.Anelementisasubstancethatcannotbebrokendownintosimplersubstances.B.ExamplesofElements•Someelementsaresolidsatroomtemperature.•Theelementsoxygenandnitrogenarethe

4、maingasesintheairyoubreathe.•Twoelementsareliquidsatroomtemperature–bromineandmercury.III.SymbolsforElementsA.Chemistsusesymbolsofoneortwoletterstorepresentelements.IV.Howdomixturesdifferfrompuresubstances?A.Acompoundalwayscontainstwoormoreelementsjoinedinafixedproportion.B.Theprop

5、ertiesofacompounddifferfromthoseofthesubstancesfromwhichitismade.1.Wateriscomposedoftheelementshydrogenandoxygen.Oxygenandhydrogenaregasesatroomtemperature,butwaterisaliquid.2.Hydrogencanfuelafire,andoxygencankeepafireburning,butwaterdoesnotburnorhelpothersubstancestoburn.V.Howdomi

6、xturesdifferfrompuresubstances?A.Thepropertiesofamixturecanvarybecausethecompositionofamixtureisnotfixed.VI.Mixturescanbeclassifiedbyhowwellthepartsofthemixturearedistributedthroughoutthemixture.A.HeterogeneousMixturesex.SALSA1.thepartsofthemixturearenoticeablydifferentfromoneanoth

7、er.B.HomogeneousMixturesexample:Kool-Aid1.thesubstancesaresoevenlydistributedthatitisdifficulttodistinguishonesubstanceinthemixturefromanother.VII.Whatisthemaindifferenceamongsolutions,suspensions,andcolloids?A.SolutionsExample:windshieldwiperfluidWhensubstancesdissolveandformahomo

8、geneousmixture,themixturet