s3 chem notes

Chapter1:ExperimentalChemistry Howarephysicalquantitiesmeasured?Physicalquantitiesinchemistry Time-SIunit:s(seconds)-60seconds=1minute-Measuredwithstopwatch Temperature-SIunit:K(kelvin)-Temperatureinkelvin=Temperatureincelsius+273-Measuredwiththermometer Length-SIunit:m(metre)-1kilometre=1000metre-Measuredwithmeasuringtape,ruler Mass-SIunit:kg(kilogram)-1kg=1000g-Measuredwithbeam,electronicbalance Volume-SIunit:m^3(cubicmetre)-1m^3=100ml-Measuredwithpipette(1d.p.),volumetricflask(bigvolume),measuringcylinder(approximate),burette(2d.p.)-Volumeofgasesaremeasuredwithagassyringe Howaregasescollected?Waterdisplacement-Gasisbubbledthroughwaterandcollectedinagasjar-Thegascanonlybeinsolubleorslightlysolubleinwater-Densitydoesnotaffectthismethod.-e.g.hydrogen,oxygen,carbondioxide

` Downwarddelivery-Gasiscollectedinagasjarandsinksdownifdenserthanair-Solubilityinwaterdoesnotaffectthismethod-Mustbedenserthanair-TheMrofairis29-e.g.chlorine,hydrogenchloride,sulfurdioxide

Upwarddelivery-Gasiscollectedinagasjarandfloatsupiflessdensethanair-Solubilityinwaterdoesnotaffectthismethod-Mustbelessdensethanair-TheMrofairis29-e.g.ammonia Calculatingthedensityofgases-Relativeatomicmass(Ar):numberofprotonsandneutronsinanatom-Therelativeatomicmassofairisaround29-Relativemolecularmass(Mr):numberofprotonsandneutronsofallatomsinamolecule-Density=mass/volume MethodsfordryinggasesConcentratedsulfuricacid-Mostgasescanbedried-Gaseswhichreactwithsulfuricacidcannotbeused-Themoistgasmustbebubbledthroughthesulfuricacid Quicklime(calciumoxide)-Mostbasicandneutralgasescanbeused,suchasammonia-Gaseswhichreacttocalciumoxidecannotbeused-Thegasmustbepassedthroughthecalciumoxide-Calciumoxidereadilyabsorbsmoisturefromtheair,soitmustbefreshlyheatedbeforeuse Fusedcalciumchloride(fusedmeansdried)

-Hydrogen,nitrogen,carbondioxideisregularlyused-Gaseswhichreactwithcalciumchloridecannotbeused-Thegasmustbepassedthroughthecalciumchloride-Calciumchloridereadilyabsorbsmoisturefromtheair,soitmustbefreshlyheatedbeforeuse Howaresubstancesinmixturesseparated?Whatisamixture?-Amixtureconsistsoftwoormoresubstancesthatarenotchemicallycombined-Thephysicalpropertiesofasubstancedeterminestheseparationtechniquesused Seperatingsolid-solidmixturesUsingmagneticattraction-Magneticsubstancescanbeseparatedfromnonmagneticsubstances-Magneticsubstances:iron,cobalt,nickel,somealloys-Wasteinalandfillisalsosortedthisway Sieving-Asieveisusedtoseparatesolidswithdifferentparticlesizes-Largeparticlescan’tpassthroughthesmallerporeswhilesmallparticlescan Usingsuitablesolvents-Solidsofdifferentsolubilityinthesolventcanbeseparated-Solvent:liquidthatdissolvessolids-Solute:solidthatdissolvesinthesolvent

-Asolutedissolvesinasolvent Sublimation-Sublimationisusedtoseparatesolidswhereonesubstancechangesfromthesolidtothegaseousstatedirectly-Substancesthatsublime:naphtalene,ammoniumchloride,iodine Separatingsolid-liquidmixturesFIltration-Seperatesaninsolublesolidfromaliquid-Aninsolublesolidisonethatisunabletodissolveintotheliquiditisplacedin-Filtrate:liquidthatpassesthroughthefilter-Residue:solidthatremainsonthefilter Evaporationtodryness-Seperatesadissolvedsolidfromitssolvent-Themixtureisheateduntilallthesolventhasvaporised

Crystallisation-Seperatesapuresolidfromitssaturatedsolution-Asaturatedsolutionisoneinwhichnomoresolutecanbedissolved-Asolutionisheateduntilitissaturated-Itisthencooledgraduallyuntilcrystalsstarttoform-Thecrystalsarethenfilteredfromthesolvent,washedwithdistilledwaterandthendriedonfilterpaper Simpledistillation-Seperatesapuresolvent(liquid)fromitssolution -Simpledistillationcanonlybeusedwhenthereisasignificantdifferenceinboilingpoint

MiscibleandimmiscibleliquidsMiscibleliquids-Miscibleliquidsareliquidswhichformauniform(homogeneous)solutionwhenmixedtogether Immiscibleliquids-Immiscibleliquidsareliquidswhichformanon-uniform(heterogenous)mixturewhenmixedtogether Seperatingliquid-liquidmixturesSeperatingfunnel-Aseparatingfunnelisusedtoseparateimmiscibleliquids-Whenaheterogenousmixtureislefttosettleintodifferentlayersinaseparatingfunnel,eachlayercanberemovedbyopeningthetapatthebottomoftheflaskandcollectingitinseparateflasksorbeakers-Thelayersareseparatedbydensity,withthedensestliquidatthebottomandthelestdenseliquidatthetop Chromatography-Chromatographycanbeusedtoseparatemiscibleliquids-Adropofahomogeneoussolutionisplacedattheedgeofapieceofpaper,andindicatedbyalinedrawnwithapencilasthestart-Itisthendippedintoasolvent,keepingthesolventjustabovethestartlevel-Asthesolventisabsorbedbythepaper,thesolutionisseparatedintopurecomponents

-Theyareseparatedbysolubilityinthesolvent,withthemostsolubleatthetopandthelestsolubleatthebottom-Thefurthestpointthesolventreacheiscalledthesolventfront-TheRfvalueofasubstanceistheratioofthedistancemovedbyasubstanceandthedistancemovedbythesolventuntilitreachesthesolventfront Fractionaldistillation-Whentwoliquidsaremiscible,theseparatingfunnelcannotbeusedtoseparatethem,andthedifferenceinboilingpointofthetwoliquidsmaybetoosmallforsimpledistillationtowork-Thus,afractionatingcolumnisaddedtothedistillationsetuptoseparatethetwoliquids-Thefractionatingcolumncontainssmallglassbeadsorothersmallsolidobjectstoprovidealargersurfaceareaforvapourstocondenseonto

Howcanthepurityofsubstancesbedetermined?-Mixturesmeltorboilatarangeoftemperatures,thusthegreateramountofimpuritiesinasubstances,thelargerthechangeinboilingormeltingpoints-Otherthanchromatography,meltingorboilingpointdatacanbeusedtodeterminethepurityofsubstances Chapter2:KineticParticleTheory Kineticparticletheory-Thekineticparticletheorystatesthatallmatterismadeupoftinyparticles,whichareinconstantrandommotion-Theseparticlesarecalledatoms,moleculesorions Solids,liquidsandgases-Basedonthekineticparticletheory,addingorremovingenergyaffectstheforcesexperiencedbytheparticles,thusdeterminingtheirphysicalstateSolids

-Particlesofasolidareverycloselypackedinanorderlymanner,thustheyonlyvibrateorrotateabouttheirfixedpositionsandhavelowkineticenergy-Theseparticleshaveexperiencestrongattractiveforces,soalotofenergyisneedtobreakuptheirorderlyarrangement-Theyhaveadefinitevolumeandshape-Theyundergomeltingwhenbeingconvertedtoaliquid,andundergosublimationwhenconvertedtoagas Liquids-Particlesofaliquidaremorespacedapartcomparedtosolids,sotheirattractiveforceislessstrong-Theirarrangementisdisorderly,unlikesolids,andcanslidepastoneanotherfreely-Theyhaveadefinitevolume,butnodefiniteshape,thustakingtheshapeoftheircontainer-Theyundergofreezingwhenbeingconvertedtoasolid,andundergoboilingorevaporationwhenconvertedtoagas Gases-Particlesofagasareveryspacedapart,havingveryweakattractiveforces-Theirarrangementisdisorderly,andtheparticlesarespacedveryfarapart-Theparticlesmovearoundquicklyandrandomly,andinanydirection-Theyhavenodefinitevolumeorshape,thustakingtheshapeoftheircontainerandbeingabletobecompressed-Theyundergocondensationwhenbeingconvertedtoaliquid Changesofstate-Whenasubstanceisheated,thermalenergyistransferredtothesubstance-Someoftheenergyisthenconvertedtokineticenergy,increasingthetemperatureofthesubstance,andviceversawhenitiscooled-Atcertaintemperatures,heatingorcoolingasubstancesresultsinachangeinstateratherthanachangeintemperature-Thesetemperaturesareknownastransitiontemperatures-Ifthetemperatureandtimeofasubstancesisplottedonagraph,wheretemperatureistheyaxisandtimeisthexaxis,itiscalledaheatingcurve-Whenthesubstanceisundergoingachangeofstate,thetemperatureofthesubstanceremainsconstantuntilallofthesubstancehaschangedstates Expansionandcontraction-Whenasubstanceisheatedbelowitsmeltingpoint,theparticlescannotspreadoutfreelyduetothestrongattractiveforce-Thus,theyvibratemorequicklyabouttheirpositions,butwithaslightlywiderspacingthanbefore,leadingtoexpansion-Whenasubstanceiscooledtheoppositehappensandtheparticlescomecloserthanbefore,leadingtocontraction