sec 3 chem

UnitsandmeasurementsPhysical quantities Apparatus AccuracyTemperature Thermometer 1 decimal placeUpto0.5degreeCelsius(E.g.37.0<totheaccuracyof oned.p.>) Mass ElectronicBalance 2decimal placeUpto0.01g(e.g.2.56tomeasuremass) Time Stopwatch Nearest Second ● Volume( liquid)➔ Measuringcylinder ( nodecimal place, approximatelynearest cm³ )➔ Pipette( 25.0cm³, 1 decimal placealways“ 0“, volumemeasuredinmultiplesof 5)➔ Burette( 2decimal place, 2nddecimal iseither “ 0“ or “ 5“ )● Volume( gas)➔ Gassyringe( dependsonthegassyringe) ● Gascollection Method Experimental set up Characteristicsof gascollected Downwarddelivery ● Gascollectedismoredensethanair ( hencethegaswill sinksolubleinwater ) Upwarddelivery ● Gascollectedislessdensethanair ( hencethegaswill floatsolubleinwater ) ©wzkai

Displacement of water ● Gascollectedisinsolubleinwater Gassyringe ● It issuitabletocollect andmeasurethevolumeof anytypeof gas KineticParticleTheory 1. (a) All matter ismadeupof tinydiscreteparticles(b) Theparticlesarealwaysinconstant randommotion 2. Stateof matter Solid Liquid GasesArrangement ofparticles Verycloselypackedinanorderlymanner Closelypackedbut not inanorderlymanner Veryfar apart andinrandomarrangement Movement ofparticles Vibrateabout infixedposition Slideover eachother Movefreelyathighspeed Attractiveforcesbetweenparticles Verystrong Strong Veryweakoralmost negligible ©wzkai

Diagrams * 4rowsx4columns* similar sizes * shouldnot haveanypattern* shouldtoucheachother* shouldnot befloatingintheair(touchingtheground) * veryfar apart* at least 6particles 3. Changesof State Examplesof sublimeare● Mothballs● Dryice( solidCO2)● Iodine ©wzkai

● Ammoniumchloride( whitesolid) 4. Determiningthestateof matter 5. Heatingandcoolingcurve MELTING CONDENSATION ATheparticlesareverycloselypackedinanorderlymanner andvibrateat their fixedposition.(Solidstate) ATheparticlesarerandomlyarrangedandmovefreelyat highspeed. (gaseousstate) A-BAsthesolidisheated, theparticlesgainkineticenergyandstart tovibratefaster. A-BAsthegasiscooled, theparticleslosekineticenergyandstart tomoveslower. B-CAmixtureof solidandliquidexistshere. Duringthemeltingprocess, thetemperatureof thesubstanceremainsconstant. All theheatenergy takeninbytheparticlesisusedto B-CAmixtureof gasandliquidexistshere. Theparticleslosekineticenergyandtheymoveslower andcloser together. ©wzkai

overcometheforcesof attraction. betweenparticles. C-DTheparticlesarerandomlyarrangedandslide over oneanother. Thesubstancebecomes liquid. C– DTheparticlesbecomecloser, randomlyarrangedandslideover oneanother. Thesubstancebecomesliquid. BOILING FREEZING CTheparticlesarecloselypackedbut not inanorderlymanner andslideover oneanother. (liquidstate) CTheparticlesarerandomlyarrangedandslide over oneanother. (liquidstate) C-DAstheliquidisheated, theparticlesgainkineticenergyandstart tovibrate/ movefaster. C– DAstheliquidiscooled, theparticleslosekinetic energyandstart toslideover oneanother slower. D-EAmixtureof liquidandgasexistshere. Duringtheboilingprocess, thetemperatureof thesubstanceremainsconstant. [ All theheat energytakeninbytheparticlesisusedtoovercometheforcesof attractionbetweenparticles. ] D– EAmixtureof liquidandsolidexistshere. Theparticles lose energy, the particles start tomovecloserandslower. E– FTheyspreadfar apart andmorerapidlyinalldirections. Thesubstanceis nowagas. E– FTheparticlesbecomecloser andvibrateabout fixedpositiononeanother. Thesubstance becomessolid. Separationtechniques1.Criteriafor purity<Element, compound>(a) Apuresubstancehas➔ Afixedmeltingandboilingpoint➔ Onlyonespot onthechromatogram(b) Animpuresubstancehas➔ Meltsandboilsover arangeof temperatures. It alsohasalower meltingpoint andhigher boilingpoint thanthepuresubstance➔ Morethanonespot onthechromatogram. Methodstotest fopurity➔ Measurem.p/ b,p➔ Conduct apaper chromatographyexperiment. ©wzkai

Boilingpoint of pureandimpuresubstances Chromatogramof pureandimpuresubstances MIXTURE Methodof separation Solid-liquidmixture; solidisinsoluble FiltrationSolidcollectedastheresidue, liquidcollected asfiltrate. Solid-liquidmixture; solidissoluble Evaporationtodryness1. Thesolutionisheatedtill dryness.(100%water removal )2. Washthecrystalsformedwithcolddistilledwater andtapdry. Crystallisation1. Thesolutionisheatedtill saturated. ( most waterbeingremoved) 2. Cooledfor thecrystalstoform.3. Washthecrystals withcolddistilledwater andtapdry. For heat-stable solid(does not decomposeonheating). Eg. sodiumchloridesalt. For heat-unstablesolid(decomposeon heating). Eg. sugar. ©wzkai

Twoimmiscibleliquids SeparatingFunnelDenser liquidiscollectedfirst fromthetap below. Twosolids, onecansublime Sublimation( Fromsolidtogaseousstate) Heat themixtureandcollect thesublimateon acoldsurface, likeaninvertedfilter funnel. Examplesof solidthat sublimeonheating:∙ Iodine∙ Ammoniumchloride∙ Carbondioxide Solid-liquid, solidissoluble Simpledistillation1. Thesolutionboilsintheflask. Boilingchipsareaddedtoensuresmoothboiling. 2. The thermometermeasures theboilingpoint of the vapourbefore it enters thecondenser. 3. In the condenser, thevapour condensesand changes fromgaseous to liquidstate. Water entersfromthe bottomandexits fromthetopofthe condenser toensure that it isfullyfilled. ( to maximiseeciency ofcondensation) 4. Liquid collected isknown as the ©wzkai

distillate. 5. The solidis left at thebottomof theflask. Twoor moremiscibleliquids Fractional distillation ∙ A liquid of higherboiling point willcondense at thefractionatingcolumnand fall back intothe flask. A liquidwith lower boilingpoint will be able topass through thefractionatingcolumn. Thisensuresseparation of liquidsaccording to theirboilingpoints. ∙ Lower boilingpointliquidiscollectedfirst distillate. ∙ Example: alcohol andwater, crudeoil Condenser– Tocondensehot vapour fromthedeliverytubetoliquidstate.Thermometer– Placedat theopeningof thedeliverytubetomeasurethetemperatureof thevapour enteringthedeliverytube.Fractionatingcolumn– It isusedtoimprovetheeciencyof fractionatingcolumn.MiscibleVsImmiscible–Miscibleliquidsareonesthat canmixtogether – likewater andethanol.Immiscibleliquidsareonesthat can't – likeoil andwater. ©wzkai

3.Paper chromatography ● Start linemust not bedrawninink/pen(drawnwithpencil )oTheink/penissolubleinthesolvent used andmayinterferewiththeresults.● Start linemust beabovethesolvent● oToensurethat thesampledoesnot dissolvedirectlyinthesolvent.● Inksamplesmust besmall dotsoToensureclear andseparatespotsare obtained.● Solvent front must beasnear tothetop edgeof thepaper aspossibleoToensurecompleteseparationof dyes Analysisof results 1 singlespot - Thesampleispure.- It hasonlyonecomponent/spot/dot. 2or morespots - Thesampleisamixture.- Fromthechromatogram, ithasthree components ©wzkai.

Remainsat start line - Thesampleisinsolubleinthesolvent used. - Toseparatethemixture, changethesolvent used. Universal solvent : water Dierent distancetravelled - Component Aismoresolubleinthesolvent thancomponent B.- Thuscomponent Atravelsfurtherawayfrom thestart line. Elements, CompoundsandMixture★ Diatomic( 2atoms) →GpVII elements, hydrogen, oxygen, nitrogen.★ Monoatomic( 1 atoms) →Gp0elements( unreactive)1. Definitionsa. Anelement isasubstancethat cannot bebrokendownintotwoor moresimpler substancesbyphysical or chemical processes. (Anelement containsonlyonetypeof atom.)b. Acompoundisasubstancemadeupof twoor moreelementscombinedtogether by chemical methods. ( oxidation, combustion, thermaldecomposition) c. Amixtureisasubstancemadeupof twoor moreconstituentswhichcanbeseparatedbyphysical methods. ( filtration, paperchromatography)i. Analloyisamixtureof ametal andother element(s).E.g. brass, bronze, steel ©wzkai