1 states of matter Alevel考试化学课件.pptx
Chapter4
StatesofmatterWhatarethethreestatesofmatterDifferencesinpropertiesofsolids,liquidsandgases
Whatarethethreestatesofmatter?
solidliquidgas
DefiniteshapeDefinitevolumeParticlesmoveveryslowlyParticlesofsolidsaretightlypacked,vibratingaboutafixedposition.solid
ThearrangementofparticlesinasolidTherearemanytypesofsolid,whosepropertiesdependontheparticlesthattheycontain.Theparticlesinasolidareveryorderlyarrangement,butevenat0K,theatomsarenotcompletelystill,theyvibrateaboutthesameaverageposition.
Indefiniteshape,definitevolumeTaketheshapeofcontainerParticlesareclosetogether,butmobileParticlesmoveslowlyliquid
HowmuchorderisthereinaliquidTheparticlesinaliquidgrouptogether,andjustthetendencyproducessomeorderintheirarrangement.However,theorderisoverarelativelyshortrange,perhapsoveradistanceof10-9m(about10moleculardiameters).Overgreaterdistances,thedegreeoforderdiminishes.Wecansummarise:inaliquidthereisshort-rangeorder,andlong-rangedisorder.
IndefiniteshapeIndefinitevolumeTaketheshapeandvolumeofcontainerParticlesarefarapartParticlesmovefastgas
HowdoweknowthatgasesaredisorderRobertBrownin1827observedthemovementofpollenonthesurfaceofwatertobecompletelyunpredictable,justlikeaverydrunkperson.Thereasonwhythegrainsbehaveinthiswayisthattheyarebeingbombardedbymoleculesintheliquid,whicharethemselvesmovinginarandomway.Around1908JeanPerrinmadeobservationsofBrownainmotioningases.ThiscouldbeexplainedalongthesamelinesasBrownianmotioninliquids.Theparticleswerebeingstruckbytherandomlymovinggasmolecules.
Thethreestatesofmatteraresolid,liquidandgas.Whetherasubstanceexistsasasolid,liquidorgasmainlydependsontwothings.1kineticenergy–whichincreasesasasubstanceisheated.