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IGCSEEdexcel
Chemistry
Exam Questions
Solids, liquids and gases in the particle model (arrangement, movement, energy)NewMelting and freezing as particle/energy changesNewBoiling and condensing as particle/energy changesNewEvaporation as particle/energy changesNewSublimation and deposition as particle/energy changesNewDilution of coloured solutions explained with particlesNewDiffusion of gases explained with particlesNewSolvent, solute, solution and saturated solutionNewSolubility in g per 100 g of solventNewPlotting solubility curvesNewInterpreting solubility curvesNewPractical: solubility of a solid in water at a specific temperatureNew
Classifying substances as element, compound or mixtureNewPure substances vs mixtures using melting/boiling behaviourNewSimple distillation: separating a solvent from a solutionNewFractional distillation: separating liquids with different boiling pointsNewFiltration: separating an insoluble solid from a liquidNewCrystallisation: obtaining a soluble solid from a solutionNewPaper chromatography: separating dissolved substancesNewReading a chromatogram to identify how many components are presentNewUsing Rf values to identify componentsNewPractical: paper chromatography using inks/food colouringsNew
How the Periodic Table is arranged by atomic numberNewGroups and periods: what they representNewDeducing electron configurations for the first 20 elementsNewUsing electrical conductivity to classify metals vs non-metalsNewUsing oxide acid–base character to classify metals vs non-metalsNewIdentifying metal/non-metal from Periodic Table positionNewLinking electron configuration to position in the Periodic TableNewWhy elements in the same group have similar chemical propertiesNewWhy noble gases are unreactiveNew
Writing word equations for reactions you’ve studiedNewWriting balanced symbol equations (including state symbols)NewCalculating Mr from Ar valuesNewThe mole as a unit for amount of substanceNewConverting between moles, mass and Mr/ArNewUsing balanced equations to calculate reacting massesNewPercentage yield calculationsNewFinding formulae experimentally: metal oxides (combustion/reduction idea)NewWater of crystallisation: recognising hydrated salts from formulaeNewEmpirical formula vs molecular formulaNewCalculating empirical formula from experimental dataNewCalculating molecular formula from empirical formula and MrNewConcentration calculations in mol/dm³NewGas volume calculations using molar volume at rtp (24 dm³)NewPractical: determine the formula of a metal oxide by combustion or reductionNew
Building a reactivity series from reactions with waterNewBuilding a reactivity series from reactions with dilute acidsNewDisplacement: metals displacing other metals from oxidesNewDisplacement: metals displacing other metals from salt solutionsNewThe required metal order in the reactivity seriesNewRusting conditions for ironNewPreventing rust: barrier methodsNewPreventing rust: galvanisingNewPreventing rust: sacrificial protectionNewOxidation, reduction and redox (oxygen transfer definitions)NewOxidation, reduction and redox (electron transfer definitions)NewOxidising agents and reducing agentsNewPractical: reactions of dilute acids with metals (Mg, Zn, Fe)New
Ores and metals in the Earth’s crustNewWhy some unreactive metals are found nativeNewExtraction by reduction with carbon (iron as the example)NewExtraction by electrolysis (aluminium as the example)NewComparing extraction methods using reactivityNewCommenting on an extraction process from unfamiliar informationNewAluminium: linking properties to usesNewCopper: linking properties to usesNewIron and steel: linking properties to usesNewTypes of steel: mild, high-carbon and stainlessNewWhat an alloy isNewWhy alloys are harder than pure metalsNew
Using litmus to identify acids and alkalisNewUsing phenolphthalein to identify acids and alkalisNewUsing methyl orange to identify acids and alkalisNewThe pH scale (0–14) and what it measuresNewClassifying solutions by pH (strong/weak acid/alkali, neutral)NewUsing universal indicator to estimate pHNewAcids as a source of hydrogen ions (H⁺) in waterNewAlkalis as a source of hydroxide ions (OH⁻) in waterNewNeutralisation as acid + alkaliNewDescribing an acid–alkali titration methodNew
Solubility rules: Group 1 and ammonium compoundsNewSolubility rules: nitratesNewSolubility rules: chlorides (including key exceptions)NewSolubility rules: sulfates (including key exceptions)NewSolubility rules: carbonates (including key exceptions)NewSolubility rules: hydroxides (including key exceptions)NewAcids and bases as proton transferNewAcid as proton donor; base as proton acceptorNewAcid + metal reactions (HCl and H₂SO₄)NewAcid + base reactions (metal oxides/hydroxides, ammonia)NewAcid + carbonate reactions (CO₂ test link)NewAlkalis vs bases (soluble bases)NewPreparing a soluble salt from an insoluble reactant (method + reasons)NewPreparing a soluble salt from an acid and alkali (method + reasons)NewPreparing an insoluble salt by precipitation (two soluble reactants)NewPractical: make hydrated copper(II) sulfate crystals from copper(II) oxideNewPractical: prepare lead(II) sulfateNew
Exothermic vs endothermic reactions (definitions)NewRecognising exothermic/endothermic from observations and temperature changeNewCalorimetry basics: measuring temperature change safely and consistentlyNewUsing Q = mcΔT to calculate heat energy changeNewConverting Q to molar enthalpy change (ΔH)NewEnergy level diagrams for exothermic reactionsNewEnergy level diagrams for endothermic reactionsNewBond breaking as endothermic; bond making as exothermicNewUsing bond energies to calculate reaction enthalpy changeNewPractical: temperature changes for dissolving, neutralisation, displacement, combustionNew
What a hydrocarbon isNewEmpirical vs molecular vs general formula in organic chemistryNewStructural vs displayed formulae (what each shows)NewHomologous series (patterns in formulae and properties)NewFunctional groups (how they define families)NewIsomerism (same formula, different structure)NewIUPAC naming rules for simple organics (up to 6 carbons)NewWriting possible structures from a molecular formulaNewClassifying reactions: substitutionNewClassifying reactions: additionNewClassifying reactions: combustionNew
Crude oil as a mixture of hydrocarbonsNewFractional distillation of crude oil (how it works)NewMain fractions: names and typical usesNewTrends across fractions: colourNewTrends across fractions: boiling pointNewTrends across fractions: viscosityNewFuels as energy-releasing substancesNewComplete combustion products of hydrocarbonsNewIncomplete combustion products of hydrocarbonsNewWhy carbon monoxide is poisonous (oxygen transport idea)NewFormation of nitrogen oxides in car engines (high temperature)NewSulfur dioxide from impurities in fuelsNewHow SO₂ and NOₓ contribute to acid rainNewCatalytic cracking (conditions and catalyst)NewWhy cracking is needed (supply and demand)New
General formula for alkanesNewSaturated hydrocarbons and what “saturated” meansNewDrawing structural formulae for alkanes up to 5 carbonsNewDrawing displayed formulae for alkanes up to 5 carbonsNewNaming unbranched alkanesNewNaming unbranched-chain isomers (up to 5 carbons)NewSubstitution with halogens under UV lightNewWriting word/symbol equations for mono-substitutionNew
The C=C functional groupNewGeneral formula for alkenesNewUnsaturated hydrocarbons and what “unsaturated” meansNewDrawing structural formulae for alkenes up to 4 carbonsNewDrawing displayed formulae for alkenes up to 4 carbonsNewNaming unbranched alkenesNewNaming unbranched-chain isomers (up to 4 carbons)NewAddition with bromine to form dibromoalkanesNewBromine water test: telling an alkane from an alkeneNew
Forming ions by electron loss and gainNewPredicting ion charges from Group number (Groups 1, 2, 3, 5, 6, 7)NewCommon named ions and charges (NH₄⁺, OH⁻, CO₃²⁻, NO₃⁻, SO₄²⁻)NewWriting ionic formulae from ion chargesNewDot-and-cross diagrams for ionic compounds (electron transfer)NewIonic bonding as electrostatic attractionNewGiant ionic lattices and high melting/boiling pointsNewConductivity: solid vs molten/aqueous ionic compoundsNew
Covalent bonds as shared pairs of electronsNewCovalent bonding as electrostatic attraction (shared pair and nuclei)NewDot-and-cross: diatomic molecules (H₂, O₂, N₂, halogens)NewDot-and-cross: hydrogen halidesNewDot-and-cross: H₂O, NH₃, CO₂NewDot-and-cross: small organics up to two carbons (methane, ethane, ethene)NewSimple molecular substances: low melting/boiling pointsNewIntermolecular forces as attractions between moleculesNewBoiling points increase with relative molecular mass (simple molecules)NewGiant covalent structures: why melting/boiling points are highNewDiamond: structure linked to hardness and conductivityNewGraphite: structure linked to conductivity and softnessNewC₆₀ fullerene: structure linked to propertiesNewWhy covalent compounds usually do not conduct electricityNew
Why covalent substances do not conduct (link to bonding)NewWhy ionic substances conduct only when molten or in solutionNewCations and anions: definitionsNewElectrolysis of molten lead(II) bromide: predicting productsNewElectrolysis of aqueous sodium chloride: predicting productsNewElectrolysis of dilute sulfuric acid: predicting productsNewElectrolysis of aqueous copper(II) sulfate: predicting productsNewWriting half-equations at the cathode and anodeNewElectrolysis as redox (oxidation at anode, reduction at cathode)NewPractical: investigating electrolysis of aqueous solutionsNew
Colours and physical states of chlorine, bromine and iodineNewTrends in Group 7 physical propertiesNewPredicting properties of other halogens from trendsNewDisplacement reactions: halogens displacing halidesNewUsing displacement to deduce reactivity orderNewExplaining Group 7 reactivity trend using electron configurationsNew
Percentages by volume of the four most abundant gases in dry airNewMeasuring oxygen percentage using metal reactions (e.g. iron)NewMeasuring oxygen percentage using non-metal reactions (e.g. phosphorus)NewCombustion in oxygen: magnesiumNewCombustion in oxygen: hydrogenNewCombustion in oxygen: sulfurNewThermal decomposition of carbonates to produce CO₂ (e.g. copper carbonate)NewCarbon dioxide as a greenhouse gasNewLinking increased CO₂ to climate change (basic understanding)NewPractical: determine oxygen percentage in airNew
Test for hydrogen (pop test)NewTest for oxygen (relights a glowing splint)NewTest for carbon dioxide (limewater)NewTest for ammonia (damp red litmus turning blue)NewTest for chlorine (bleaches damp litmus)NewFlame test method (how to carry it out)NewFlame test colours: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺NewTest for NH₄⁺ using sodium hydroxide and the gas producedNewTest for Cu²⁺ using sodium hydroxide (precipitate)NewTest for Fe²⁺ using sodium hydroxide (precipitate)NewTest for Fe³⁺ using sodium hydroxide (precipitate)NewTest for Cl⁻/Br⁻/I⁻ using acidified silver nitrateNewTest for SO₄²⁻ using acidified barium chlorideNewTest for CO₃²⁻ using hydrochloric acid and identifying CO₂NewTest for water using anhydrous copper(II) sulfateNewPhysical purity test for water (sharp melting/boiling point)New
Measuring rate: what you can observe and recordNewDesigning rate experiments (variables and fair testing)NewSurface area effect on rate (describing and explaining)NewConcentration effect on rate (describing and explaining)NewTemperature effect on rate (describing and explaining)NewPressure effect on rate (gases) (describing and explaining)NewCatalysts: definition and what “unchanged” meansNewCollision theory: linking rate to collision frequency and energyNewCatalysts and activation energy (alternative pathway)NewReaction profile diagrams showing ΔH and activation energyNewPractical: marble chips + hydrochloric acid (surface area and concentration)NewPractical: catalytic decomposition of hydrogen peroxideNew
Identifying reversible reactions and using the ⇌ symbolNewReversible: hydrated copper(II) sulfate dehydration/rehydrationNewReversible: heating ammonium chlorideNewDynamic equilibrium in a sealed containerNewFeatures of dynamic equilibrium (equal rates; constant concentrations)NewWhy a catalyst does not change the position of equilibriumNewTemperature changes and equilibrium position (endo/exo direction)NewPressure changes and equilibrium position (moles of gas idea)New
The −OH functional groupNewDrawing and naming methanolNewDrawing and naming ethanolNewDrawing and naming propan-1-ol (propanol)NewDrawing and naming butan-1-ol (butanol)NewEthanol oxidation by complete combustionNewEthanol oxidation by microbial oxidation to ethanoic acidNewEthanol oxidation using acidified potassium dichromate(VI)NewManufacturing ethanol by hydration of ethene (conditions and catalyst)NewManufacturing ethanol by fermentation of glucose (conditions)NewWhy fermentation needs no air and an optimum temperatureNew
The ester functional groupNewMaking ethyl ethanoate from ethanol + ethanoic acid (acid catalyst)NewStructural and displayed formula of ethyl ethanoateNewWorking out an ester structure from the alcohol + carboxylic acidNewWorking backwards from an ester to its alcohol + carboxylic acidNewEsters as volatile substances with distinctive smellsNewEster uses: food flavourings and perfumesNewPractical: preparing an ester (e.g. ethyl ethanoate)New
Addition polymerisation and the idea of monomersNewDrawing repeat units: poly(ethene)NewDrawing repeat units: poly(propene)NewDrawing repeat units: poly(chloroethene)NewDrawing repeat units: (poly)tetrafluoroetheneNewDeducing a monomer from an addition polymer repeat unitNewDeducing a repeat unit from a monomerNewDisposal problems: inertness and non-biodegradabilityNewDisposal problems: toxic gases from burning some polymersNewCondensation polymerisation: diol + dicarboxylic acid → polyester + waterNewWriting a polyester repeat unit from given monomers (incl. ethanedioic acid + ethanediol)NewBiopolyesters and biodegradabilityNew
Turning a research question into a testable hypothesisNewIdentifying independent, dependent and control variablesNewChoosing apparatus and measurement methods for precisionNewRecording observations in a clear, repeatable methodNewPresenting data in tables with headings and unitsNewPlotting graphs with sensible scales and labelled axesNewDrawing conclusions that match the evidenceNewSpotting anomalies and suggesting reasonsNewReliability: repeats and identifying random errorNewAccuracy vs precision (and how to improve both)NewValidity: controlling variables and fair testingNewEvaluating a method (limitations, improvements)NewSafe practical technique and risk control in chemistry contextsNew
Using decimal numbers and standard form in chemistry contextsNewRatios, fractions and percentages in chemistry problems (yield, composition)NewUsing appropriate significant figuresNewUsing means/averages for repeated measurementsNewBar charts and frequency representations for dataNewScatter graphs to identify patterns and trendsNewChanging the subject of an equation (e.g. Q = mcΔT, concentration equations)NewSubstituting values with correct unitsNewSolving simple equations for unknownsNewFinding gradient and intercept from linear graphsNewUsing a tangent to estimate rate of change on a curveNewEstimating area under a curve by counting squaresNew
Thermal decomposition of different carbonates (compare ease)NewComparing energy released by different fuels (temperature rise)NewBurning candles: air used up and products formedNewCalcium compounds: CaCO₃ decomposition; CaO + water; CaCO₃ + acidNewNeutralisation reactions using oxides/hydroxides/carbonatesNewElectrolysis of seawater or acidified waterNewInvestigating rusting of iron (variables and prevention)NewOxidation/reduction in combustion and competition reactionsNewFractional distillation of synthetic crude oil (fractions + properties)NewCracking paraffin oilNewTesting precipitate predictions when mixing soluble saltsNewIon tests to identify unknown compoundsNewHeating a hydrated salt to find water of crystallisationNew
