Explore
IGCSEEdexcel
Chemistry
Start learning
Browse allCurriculum Modules
Solids, liquids and gases in the particle model (arrangement, movement, energy)Melting and freezing as particle/energy changesBoiling and condensing as particle/energy changesEvaporation as particle/energy changesSublimation and deposition as particle/energy changesDilution of coloured solutions explained with particlesDiffusion of gases explained with particlesSolvent, solute, solution and saturated solutionSolubility in g per 100 g of solventPlotting solubility curvesInterpreting solubility curvesPractical: solubility of a solid in water at a specific temperature
Classifying substances as element, compound or mixturePure substances vs mixtures using melting/boiling behaviourSimple distillation: separating a solvent from a solutionFractional distillation: separating liquids with different boiling pointsFiltration: separating an insoluble solid from a liquidCrystallisation: obtaining a soluble solid from a solutionPaper chromatography: separating dissolved substancesReading a chromatogram to identify how many components are presentUsing Rf values to identify componentsPractical: paper chromatography using inks/food colourings
How the Periodic Table is arranged by atomic numberGroups and periods: what they representDeducing electron configurations for the first 20 elementsUsing electrical conductivity to classify metals vs non-metalsUsing oxide acid–base character to classify metals vs non-metalsIdentifying metal/non-metal from Periodic Table positionLinking electron configuration to position in the Periodic TableWhy elements in the same group have similar chemical propertiesWhy noble gases are unreactive
Writing word equations for reactions you’ve studiedWriting balanced symbol equations (including state symbols)Calculating Mr from Ar valuesThe mole as a unit for amount of substanceConverting between moles, mass and Mr/ArUsing balanced equations to calculate reacting massesPercentage yield calculationsFinding formulae experimentally: metal oxides (combustion/reduction idea)Water of crystallisation: recognising hydrated salts from formulaeEmpirical formula vs molecular formulaCalculating empirical formula from experimental dataCalculating molecular formula from empirical formula and MrConcentration calculations in mol/dm³Gas volume calculations using molar volume at rtp (24 dm³)Practical: determine the formula of a metal oxide by combustion or reduction
Building a reactivity series from reactions with waterBuilding a reactivity series from reactions with dilute acidsDisplacement: metals displacing other metals from oxidesDisplacement: metals displacing other metals from salt solutionsThe required metal order in the reactivity seriesRusting conditions for ironPreventing rust: barrier methodsPreventing rust: galvanisingPreventing rust: sacrificial protectionOxidation, reduction and redox (oxygen transfer definitions)Oxidation, reduction and redox (electron transfer definitions)Oxidising agents and reducing agentsPractical: reactions of dilute acids with metals (Mg, Zn, Fe)
Ores and metals in the Earth’s crustWhy some unreactive metals are found nativeExtraction by reduction with carbon (iron as the example)Extraction by electrolysis (aluminium as the example)Comparing extraction methods using reactivityCommenting on an extraction process from unfamiliar informationAluminium: linking properties to usesCopper: linking properties to usesIron and steel: linking properties to usesTypes of steel: mild, high-carbon and stainlessWhat an alloy isWhy alloys are harder than pure metals
Using litmus to identify acids and alkalisUsing phenolphthalein to identify acids and alkalisUsing methyl orange to identify acids and alkalisThe pH scale (0–14) and what it measuresClassifying solutions by pH (strong/weak acid/alkali, neutral)Using universal indicator to estimate pHAcids as a source of hydrogen ions (H⁺) in waterAlkalis as a source of hydroxide ions (OH⁻) in waterNeutralisation as acid + alkaliDescribing an acid–alkali titration method
Solubility rules: Group 1 and ammonium compoundsSolubility rules: nitratesSolubility rules: chlorides (including key exceptions)Solubility rules: sulfates (including key exceptions)Solubility rules: carbonates (including key exceptions)Solubility rules: hydroxides (including key exceptions)Acids and bases as proton transferAcid as proton donor; base as proton acceptorAcid + metal reactions (HCl and H₂SO₄)Acid + base reactions (metal oxides/hydroxides, ammonia)Acid + carbonate reactions (CO₂ test link)Alkalis vs bases (soluble bases)Preparing a soluble salt from an insoluble reactant (method + reasons)Preparing a soluble salt from an acid and alkali (method + reasons)Preparing an insoluble salt by precipitation (two soluble reactants)Practical: make hydrated copper(II) sulfate crystals from copper(II) oxidePractical: prepare lead(II) sulfate
Exothermic vs endothermic reactions (definitions)Recognising exothermic/endothermic from observations and temperature changeCalorimetry basics: measuring temperature change safely and consistentlyUsing Q = mcΔT to calculate heat energy changeConverting Q to molar enthalpy change (ΔH)Energy level diagrams for exothermic reactionsEnergy level diagrams for endothermic reactionsBond breaking as endothermic; bond making as exothermicUsing bond energies to calculate reaction enthalpy changePractical: temperature changes for dissolving, neutralisation, displacement, combustion
What a hydrocarbon isEmpirical vs molecular vs general formula in organic chemistryStructural vs displayed formulae (what each shows)Homologous series (patterns in formulae and properties)Functional groups (how they define families)Isomerism (same formula, different structure)IUPAC naming rules for simple organics (up to 6 carbons)Writing possible structures from a molecular formulaClassifying reactions: substitutionClassifying reactions: additionClassifying reactions: combustion
Crude oil as a mixture of hydrocarbonsFractional distillation of crude oil (how it works)Main fractions: names and typical usesTrends across fractions: colourTrends across fractions: boiling pointTrends across fractions: viscosityFuels as energy-releasing substancesComplete combustion products of hydrocarbonsIncomplete combustion products of hydrocarbonsWhy carbon monoxide is poisonous (oxygen transport idea)Formation of nitrogen oxides in car engines (high temperature)Sulfur dioxide from impurities in fuelsHow SO₂ and NOₓ contribute to acid rainCatalytic cracking (conditions and catalyst)Why cracking is needed (supply and demand)
General formula for alkanesSaturated hydrocarbons and what “saturated” meansDrawing structural formulae for alkanes up to 5 carbonsDrawing displayed formulae for alkanes up to 5 carbonsNaming unbranched alkanesNaming unbranched-chain isomers (up to 5 carbons)Substitution with halogens under UV lightWriting word/symbol equations for mono-substitution
The C=C functional groupGeneral formula for alkenesUnsaturated hydrocarbons and what “unsaturated” meansDrawing structural formulae for alkenes up to 4 carbonsDrawing displayed formulae for alkenes up to 4 carbonsNaming unbranched alkenesNaming unbranched-chain isomers (up to 4 carbons)Addition with bromine to form dibromoalkanesBromine water test: telling an alkane from an alkene
Forming ions by electron loss and gainPredicting ion charges from Group number (Groups 1, 2, 3, 5, 6, 7)Common named ions and charges (NH₄⁺, OH⁻, CO₃²⁻, NO₃⁻, SO₄²⁻)Writing ionic formulae from ion chargesDot-and-cross diagrams for ionic compounds (electron transfer)Ionic bonding as electrostatic attractionGiant ionic lattices and high melting/boiling pointsConductivity: solid vs molten/aqueous ionic compounds
Covalent bonds as shared pairs of electronsCovalent bonding as electrostatic attraction (shared pair and nuclei)Dot-and-cross: diatomic molecules (H₂, O₂, N₂, halogens)Dot-and-cross: hydrogen halidesDot-and-cross: H₂O, NH₃, CO₂Dot-and-cross: small organics up to two carbons (methane, ethane, ethene)Simple molecular substances: low melting/boiling pointsIntermolecular forces as attractions between moleculesBoiling points increase with relative molecular mass (simple molecules)Giant covalent structures: why melting/boiling points are highDiamond: structure linked to hardness and conductivityGraphite: structure linked to conductivity and softnessC₆₀ fullerene: structure linked to propertiesWhy covalent compounds usually do not conduct electricity
Why covalent substances do not conduct (link to bonding)Why ionic substances conduct only when molten or in solutionCations and anions: definitionsElectrolysis of molten lead(II) bromide: predicting productsElectrolysis of aqueous sodium chloride: predicting productsElectrolysis of dilute sulfuric acid: predicting productsElectrolysis of aqueous copper(II) sulfate: predicting productsWriting half-equations at the cathode and anodeElectrolysis as redox (oxidation at anode, reduction at cathode)Practical: investigating electrolysis of aqueous solutions
Colours and physical states of chlorine, bromine and iodineTrends in Group 7 physical propertiesPredicting properties of other halogens from trendsDisplacement reactions: halogens displacing halidesUsing displacement to deduce reactivity orderExplaining Group 7 reactivity trend using electron configurations
Percentages by volume of the four most abundant gases in dry airMeasuring oxygen percentage using metal reactions (e.g. iron)Measuring oxygen percentage using non-metal reactions (e.g. phosphorus)Combustion in oxygen: magnesiumCombustion in oxygen: hydrogenCombustion in oxygen: sulfurThermal decomposition of carbonates to produce CO₂ (e.g. copper carbonate)Carbon dioxide as a greenhouse gasLinking increased CO₂ to climate change (basic understanding)Practical: determine oxygen percentage in air
Test for hydrogen (pop test)Test for oxygen (relights a glowing splint)Test for carbon dioxide (limewater)Test for ammonia (damp red litmus turning blue)Test for chlorine (bleaches damp litmus)Flame test method (how to carry it out)Flame test colours: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺Test for NH₄⁺ using sodium hydroxide and the gas producedTest for Cu²⁺ using sodium hydroxide (precipitate)Test for Fe²⁺ using sodium hydroxide (precipitate)Test for Fe³⁺ using sodium hydroxide (precipitate)Test for Cl⁻/Br⁻/I⁻ using acidified silver nitrateTest for SO₄²⁻ using acidified barium chlorideTest for CO₃²⁻ using hydrochloric acid and identifying CO₂Test for water using anhydrous copper(II) sulfatePhysical purity test for water (sharp melting/boiling point)
Measuring rate: what you can observe and recordDesigning rate experiments (variables and fair testing)Surface area effect on rate (describing and explaining)Concentration effect on rate (describing and explaining)Temperature effect on rate (describing and explaining)Pressure effect on rate (gases) (describing and explaining)Catalysts: definition and what “unchanged” meansCollision theory: linking rate to collision frequency and energyCatalysts and activation energy (alternative pathway)Reaction profile diagrams showing ΔH and activation energyPractical: marble chips + hydrochloric acid (surface area and concentration)Practical: catalytic decomposition of hydrogen peroxide
Identifying reversible reactions and using the ⇌ symbolReversible: hydrated copper(II) sulfate dehydration/rehydrationReversible: heating ammonium chlorideDynamic equilibrium in a sealed containerFeatures of dynamic equilibrium (equal rates; constant concentrations)Why a catalyst does not change the position of equilibriumTemperature changes and equilibrium position (endo/exo direction)Pressure changes and equilibrium position (moles of gas idea)
The −OH functional groupDrawing and naming methanolDrawing and naming ethanolDrawing and naming propan-1-ol (propanol)Drawing and naming butan-1-ol (butanol)Ethanol oxidation by complete combustionEthanol oxidation by microbial oxidation to ethanoic acidEthanol oxidation using acidified potassium dichromate(VI)Manufacturing ethanol by hydration of ethene (conditions and catalyst)Manufacturing ethanol by fermentation of glucose (conditions)Why fermentation needs no air and an optimum temperature
The ester functional groupMaking ethyl ethanoate from ethanol + ethanoic acid (acid catalyst)Structural and displayed formula of ethyl ethanoateWorking out an ester structure from the alcohol + carboxylic acidWorking backwards from an ester to its alcohol + carboxylic acidEsters as volatile substances with distinctive smellsEster uses: food flavourings and perfumesPractical: preparing an ester (e.g. ethyl ethanoate)
Addition polymerisation and the idea of monomersDrawing repeat units: poly(ethene)Drawing repeat units: poly(propene)Drawing repeat units: poly(chloroethene)Drawing repeat units: (poly)tetrafluoroetheneDeducing a monomer from an addition polymer repeat unitDeducing a repeat unit from a monomerDisposal problems: inertness and non-biodegradabilityDisposal problems: toxic gases from burning some polymersCondensation polymerisation: diol + dicarboxylic acid → polyester + waterWriting a polyester repeat unit from given monomers (incl. ethanedioic acid + ethanediol)Biopolyesters and biodegradability
Turning a research question into a testable hypothesisIdentifying independent, dependent and control variablesChoosing apparatus and measurement methods for precisionRecording observations in a clear, repeatable methodPresenting data in tables with headings and unitsPlotting graphs with sensible scales and labelled axesDrawing conclusions that match the evidenceSpotting anomalies and suggesting reasonsReliability: repeats and identifying random errorAccuracy vs precision (and how to improve both)Validity: controlling variables and fair testingEvaluating a method (limitations, improvements)Safe practical technique and risk control in chemistry contexts
Using decimal numbers and standard form in chemistry contextsRatios, fractions and percentages in chemistry problems (yield, composition)Using appropriate significant figuresUsing means/averages for repeated measurementsBar charts and frequency representations for dataScatter graphs to identify patterns and trendsChanging the subject of an equation (e.g. Q = mcΔT, concentration equations)Substituting values with correct unitsSolving simple equations for unknownsFinding gradient and intercept from linear graphsUsing a tangent to estimate rate of change on a curveEstimating area under a curve by counting squares
Thermal decomposition of different carbonates (compare ease)Comparing energy released by different fuels (temperature rise)Burning candles: air used up and products formedCalcium compounds: CaCO₃ decomposition; CaO + water; CaCO₃ + acidNeutralisation reactions using oxides/hydroxides/carbonatesElectrolysis of seawater or acidified waterInvestigating rusting of iron (variables and prevention)Oxidation/reduction in combustion and competition reactionsFractional distillation of synthetic crude oil (fractions + properties)Cracking paraffin oilTesting precipitate predictions when mixing soluble saltsIon tests to identify unknown compoundsHeating a hydrated salt to find water of crystallisation
