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-Aninsolublesolidisonethatisunabletodissolveintotheliquiditisplace