Edexcel · IGCSE
Your journey to excellence inChemistry
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Solids, liquids and gases in the particle model (arrangement, movement, energy)
1Solids, liquids and gases in the particle model (arrangement, movement, energy)Read next2Melting and freezing as particle/energy changesRead next3Boiling and condensing as particle/energy changesRead next4Evaporation as particle/energy changesRead next5Sublimation and deposition as particle/energy changesRead next6Dilution of coloured solutions explained with particlesRead next7Diffusion of gases explained with particlesRead next8Solvent, solute, solution and saturated solutionRead next9Solubility in g per 100 g of solventRead next10Plotting solubility curvesRead next11Interpreting solubility curvesRead next12Practical: solubility of a solid in water at a specific temperatureRead next
Classifying substances as element, compound or mixture
1Classifying substances as element, compound or mixtureRead next2Pure substances vs mixtures using melting/boiling behaviourRead next3Simple distillation: separating a solvent from a solutionRead next4Fractional distillation: separating liquids with different boiling pointsRead next5Filtration: separating an insoluble solid from a liquidRead next6Crystallisation: obtaining a soluble solid from a solutionRead next7Paper chromatography: separating dissolved substancesRead next8Reading a chromatogram to identify how many components are presentRead next9Using Rf values to identify componentsRead next10Practical: paper chromatography using inks/food colouringsRead next
What “atom” and “molecule” mean
1What “atom” and “molecule” meanRead next2Subatomic particles: positions, relative masses and relative chargesRead next3Atomic number and mass numberRead next4Isotopes: what changes (neutrons) vs what stays the same (protons)Read next5Relative atomic mass (Ar) as a weighted meanRead next6Calculating Ar from isotopic abundancesRead next
How the Periodic Table is arranged by atomic number
1How the Periodic Table is arranged by atomic numberRead next2Groups and periods: what they representRead next3Deducing electron configurations for the first 20 elementsRead next4Using electrical conductivity to classify metals vs non-metalsRead next5Using oxide acid–base character to classify metals vs non-metalsRead next6Identifying metal/non-metal from Periodic Table positionRead next7Linking electron configuration to position in the Periodic TableRead next8Why elements in the same group have similar chemical propertiesRead next9Why noble gases are unreactiveRead next
Writing word equations for reactions you’ve studied
1Writing word equations for reactions you’ve studiedRead next2Writing balanced symbol equations (including state symbols)Read next3Calculating Mr from Ar valuesRead next4The mole as a unit for amount of substanceRead next5Converting between moles, mass and Mr/ArRead next6Using balanced equations to calculate reacting massesRead next7Percentage yield calculationsRead next8Finding formulae experimentally: metal oxides (combustion/reduction idea)Read next9Water of crystallisation: recognising hydrated salts from formulaeRead next10Empirical formula vs molecular formulaRead next11Calculating empirical formula from experimental dataRead next12Calculating molecular formula from empirical formula and MrRead next13Concentration calculations in mol/dm³Read next14Gas volume calculations using molar volume at rtp (24 dm³)Read next15Practical: determine the formula of a metal oxide by combustion or reductionRead next
Building a reactivity series from reactions with water
1Building a reactivity series from reactions with waterRead next2Building a reactivity series from reactions with dilute acidsRead next3Displacement: metals displacing other metals from oxidesRead next4Displacement: metals displacing other metals from salt solutionsRead next5The required metal order in the reactivity seriesRead next6Rusting conditions for ironRead next7Preventing rust: barrier methodsRead next8Preventing rust: galvanisingRead next9Preventing rust: sacrificial protectionRead next10Oxidation, reduction and redox (oxygen transfer definitions)Read next11Oxidation, reduction and redox (electron transfer definitions)Read next12Oxidising agents and reducing agentsRead next13Practical: reactions of dilute acids with metals (Mg, Zn, Fe)Read next
Ores and metals in the Earth’s crust
1Ores and metals in the Earth’s crustRead next2Why some unreactive metals are found nativeRead next3Extraction by reduction with carbon (iron as the example)Read next4Extraction by electrolysis (aluminium as the example)Read next5Comparing extraction methods using reactivityRead next6Commenting on an extraction process from unfamiliar informationRead next7Aluminium: linking properties to usesRead next8Copper: linking properties to usesRead next9Iron and steel: linking properties to usesRead next10Types of steel: mild, high-carbon and stainlessRead next11What an alloy isRead next12Why alloys are harder than pure metalsRead next
Using litmus to identify acids and alkalis
1Using litmus to identify acids and alkalisRead next2Using phenolphthalein to identify acids and alkalisRead next3Using methyl orange to identify acids and alkalisRead next4The pH scale (0–14) and what it measuresRead next5Classifying solutions by pH (strong/weak acid/alkali, neutral)Read next6Using universal indicator to estimate pHRead next7Acids as a source of hydrogen ions (H⁺) in waterRead next8Alkalis as a source of hydroxide ions (OH⁻) in waterRead next9Neutralisation as acid + alkaliRead next10Describing an acid–alkali titration methodRead next
Solubility rules: Group 1 and ammonium compounds
1Solubility rules: Group 1 and ammonium compoundsRead next2Solubility rules: nitratesRead next3Solubility rules: chlorides (including key exceptions)Read next4Solubility rules: sulfates (including key exceptions)Read next5Solubility rules: carbonates (including key exceptions)Read next6Solubility rules: hydroxides (including key exceptions)Read next7Acids and bases as proton transferRead next8Acid as proton donor; base as proton acceptorRead next9Acid + metal reactions (HCl and H₂SO₄)Read next10Acid + base reactions (metal oxides/hydroxides, ammonia)Read next11Acid + carbonate reactions (CO₂ test link)Read next12Alkalis vs bases (soluble bases)Read next13Preparing a soluble salt from an insoluble reactant (method + reasons)Read next14Preparing a soluble salt from an acid and alkali (method + reasons)Read next15Preparing an insoluble salt by precipitation (two soluble reactants)Read next16Practical: make hydrated copper(II) sulfate crystals from copper(II) oxideRead next17Practical: prepare lead(II) sulfateRead next
Exothermic vs endothermic reactions (definitions)
1Exothermic vs endothermic reactions (definitions)Read next2Recognising exothermic/endothermic from observations and temperature changeRead next3Calorimetry basics: measuring temperature change safely and consistentlyRead next4Using Q = mcΔT to calculate heat energy changeRead next5Converting Q to molar enthalpy change (ΔH)Read next6Energy level diagrams for exothermic reactionsRead next7Energy level diagrams for endothermic reactionsRead next8Bond breaking as endothermic; bond making as exothermicRead next9Using bond energies to calculate reaction enthalpy changeRead next10Practical: temperature changes for dissolving, neutralisation, displacement, combustionRead next
What a hydrocarbon is
1What a hydrocarbon isRead next2Empirical vs molecular vs general formula in organic chemistryRead next3Structural vs displayed formulae (what each shows)Read next4Homologous series (patterns in formulae and properties)Read next5Functional groups (how they define families)Read next6Isomerism (same formula, different structure)Read next7IUPAC naming rules for simple organics (up to 6 carbons)Read next8Writing possible structures from a molecular formulaRead next9Classifying reactions: substitutionRead next10Classifying reactions: additionRead next11Classifying reactions: combustionRead next
Crude oil as a mixture of hydrocarbons
1Crude oil as a mixture of hydrocarbonsRead next2Fractional distillation of crude oil (how it works)Read next3Main fractions: names and typical usesRead next4Trends across fractions: colourRead next5Trends across fractions: boiling pointRead next6Trends across fractions: viscosityRead next7Fuels as energy-releasing substancesRead next8Complete combustion products of hydrocarbonsRead next9Incomplete combustion products of hydrocarbonsRead next10Why carbon monoxide is poisonous (oxygen transport idea)Read next11Formation of nitrogen oxides in car engines (high temperature)Read next12Sulfur dioxide from impurities in fuelsRead next13How SO₂ and NOₓ contribute to acid rainRead next14Catalytic cracking (conditions and catalyst)Read next15Why cracking is needed (supply and demand)Read next
General formula for alkanes
1General formula for alkanesRead next2Saturated hydrocarbons and what “saturated” meansRead next3Drawing structural formulae for alkanes up to 5 carbonsRead next4Drawing displayed formulae for alkanes up to 5 carbonsRead next5Naming unbranched alkanesRead next6Naming unbranched-chain isomers (up to 5 carbons)Read next7Substitution with halogens under UV lightRead next8Writing word/symbol equations for mono-substitutionRead next
The C=C functional group
1The C=C functional groupRead next2General formula for alkenesRead next3Unsaturated hydrocarbons and what “unsaturated” meansRead next4Drawing structural formulae for alkenes up to 4 carbonsRead next5Drawing displayed formulae for alkenes up to 4 carbonsRead next6Naming unbranched alkenesRead next7Naming unbranched-chain isomers (up to 4 carbons)Read next8Addition with bromine to form dibromoalkanesRead next9Bromine water test: telling an alkane from an alkeneRead next
Forming ions by electron loss and gain
1Forming ions by electron loss and gainRead next2Predicting ion charges from Group number (Groups 1, 2, 3, 5, 6, 7)Read next3Common named ions and charges (NH₄⁺, OH⁻, CO₃²⁻, NO₃⁻, SO₄²⁻)Read next4Writing ionic formulae from ion chargesRead next5Dot-and-cross diagrams for ionic compounds (electron transfer)Read next6Ionic bonding as electrostatic attractionRead next7Giant ionic lattices and high melting/boiling pointsRead next8Conductivity: solid vs molten/aqueous ionic compoundsRead next
Covalent bonds as shared pairs of electrons
1Covalent bonds as shared pairs of electronsRead next2Covalent bonding as electrostatic attraction (shared pair and nuclei)Read next3Dot-and-cross: diatomic molecules (H₂, O₂, N₂, halogens)Read next4Dot-and-cross: hydrogen halidesRead next5Dot-and-cross: H₂O, NH₃, CO₂Read next6Dot-and-cross: small organics up to two carbons (methane, ethane, ethene)Read next7Simple molecular substances: low melting/boiling pointsRead next8Intermolecular forces as attractions between moleculesRead next9Boiling points increase with relative molecular mass (simple molecules)Read next10Giant covalent structures: why melting/boiling points are highRead next11Diamond: structure linked to hardness and conductivityRead next12Graphite: structure linked to conductivity and softnessRead next13C₆₀ fullerene: structure linked to propertiesRead next14Why covalent compounds usually do not conduct electricityRead next
Representing a metallic lattice in 2D
Why covalent substances do not conduct (link to bonding)
1Why covalent substances do not conduct (link to bonding)Read next2Why ionic substances conduct only when molten or in solutionRead next3Cations and anions: definitionsRead next4Electrolysis of molten lead(II) bromide: predicting productsRead next5Electrolysis of aqueous sodium chloride: predicting productsRead next6Electrolysis of dilute sulfuric acid: predicting productsRead next7Electrolysis of aqueous copper(II) sulfate: predicting productsRead next8Writing half-equations at the cathode and anodeRead next9Electrolysis as redox (oxidation at anode, reduction at cathode)Read next10Practical: investigating electrolysis of aqueous solutionsRead next
Similar reactions with water as evidence of a “family”
Colours and physical states of chlorine, bromine and iodine
1Colours and physical states of chlorine, bromine and iodineRead next2Trends in Group 7 physical propertiesRead next3Predicting properties of other halogens from trendsRead next4Displacement reactions: halogens displacing halidesRead next5Using displacement to deduce reactivity orderRead next6Explaining Group 7 reactivity trend using electron configurationsRead next
Percentages by volume of the four most abundant gases in dry air
1Percentages by volume of the four most abundant gases in dry airRead next2Measuring oxygen percentage using metal reactions (e.g. iron)Read next3Measuring oxygen percentage using non-metal reactions (e.g. phosphorus)Read next4Combustion in oxygen: magnesiumRead next5Combustion in oxygen: hydrogenRead next6Combustion in oxygen: sulfurRead next7Thermal decomposition of carbonates to produce CO₂ (e.g. copper carbonate)Read next8Carbon dioxide as a greenhouse gasRead next9Linking increased CO₂ to climate change (basic understanding)Read next10Practical: determine oxygen percentage in airRead next
Test for hydrogen (pop test)
1Test for hydrogen (pop test)Read next2Test for oxygen (relights a glowing splint)Read next3Test for carbon dioxide (limewater)Read next4Test for ammonia (damp red litmus turning blue)Read next5Test for chlorine (bleaches damp litmus)Read next6Flame test method (how to carry it out)Read next7Flame test colours: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺Read next8Test for NH₄⁺ using sodium hydroxide and the gas producedRead next9Test for Cu²⁺ using sodium hydroxide (precipitate)Read next10Test for Fe²⁺ using sodium hydroxide (precipitate)Read next11Test for Fe³⁺ using sodium hydroxide (precipitate)Read next12Test for Cl⁻/Br⁻/I⁻ using acidified silver nitrateRead next13Test for SO₄²⁻ using acidified barium chlorideRead next14Test for CO₃²⁻ using hydrochloric acid and identifying CO₂Read next15Test for water using anhydrous copper(II) sulfateRead next16Physical purity test for water (sharp melting/boiling point)Read next
Measuring rate: what you can observe and record
1Measuring rate: what you can observe and recordRead next2Designing rate experiments (variables and fair testing)Read next3Surface area effect on rate (describing and explaining)Read next4Concentration effect on rate (describing and explaining)Read next5Temperature effect on rate (describing and explaining)Read next6Pressure effect on rate (gases) (describing and explaining)Read next7Catalysts: definition and what “unchanged” meansRead next8Collision theory: linking rate to collision frequency and energyRead next9Catalysts and activation energy (alternative pathway)Read next10Reaction profile diagrams showing ΔH and activation energyRead next11Practical: marble chips + hydrochloric acid (surface area and concentration)Read next12Practical: catalytic decomposition of hydrogen peroxideRead next
Identifying reversible reactions and using the ⇌ symbol
1Identifying reversible reactions and using the ⇌ symbolRead next2Reversible: hydrated copper(II) sulfate dehydration/rehydrationRead next3Reversible: heating ammonium chlorideRead next4Dynamic equilibrium in a sealed containerRead next5Features of dynamic equilibrium (equal rates; constant concentrations)Read next6Why a catalyst does not change the position of equilibriumRead next7Temperature changes and equilibrium position (endo/exo direction)Read next8Pressure changes and equilibrium position (moles of gas idea)Read next
The −OH functional group
1The −OH functional groupRead next2Drawing and naming methanolRead next3Drawing and naming ethanolRead next4Drawing and naming propan-1-ol (propanol)Read next5Drawing and naming butan-1-ol (butanol)Read next6Ethanol oxidation by complete combustionRead next7Ethanol oxidation by microbial oxidation to ethanoic acidRead next8Ethanol oxidation using acidified potassium dichromate(VI)Read next9Manufacturing ethanol by hydration of ethene (conditions and catalyst)Read next10Manufacturing ethanol by fermentation of glucose (conditions)Read next11Why fermentation needs no air and an optimum temperatureRead next
The ester functional group
1The ester functional groupRead next2Making ethyl ethanoate from ethanol + ethanoic acid (acid catalyst)Read next3Structural and displayed formula of ethyl ethanoateRead next4Working out an ester structure from the alcohol + carboxylic acidRead next5Working backwards from an ester to its alcohol + carboxylic acidRead next6Esters as volatile substances with distinctive smellsRead next7Ester uses: food flavourings and perfumesRead next8Practical: preparing an ester (e.g. ethyl ethanoate)Read next
Addition polymerisation and the idea of monomers
1Addition polymerisation and the idea of monomersRead next2Drawing repeat units: poly(ethene)Read next3Drawing repeat units: poly(propene)Read next4Drawing repeat units: poly(chloroethene)Read next5Drawing repeat units: (poly)tetrafluoroetheneRead next6Deducing a monomer from an addition polymer repeat unitRead next7Deducing a repeat unit from a monomerRead next8Disposal problems: inertness and non-biodegradabilityRead next9Disposal problems: toxic gases from burning some polymersRead next10Condensation polymerisation: diol + dicarboxylic acid → polyester + waterRead next11Writing a polyester repeat unit from given monomers (incl. ethanedioic acid + ethanediol)Read next12Biopolyesters and biodegradabilityRead next
Turning a research question into a testable hypothesis
1Turning a research question into a testable hypothesisRead next2Identifying independent, dependent and control variablesRead next3Choosing apparatus and measurement methods for precisionRead next4Recording observations in a clear, repeatable methodRead next5Presenting data in tables with headings and unitsRead next6Plotting graphs with sensible scales and labelled axesRead next7Drawing conclusions that match the evidenceRead next8Spotting anomalies and suggesting reasonsRead next9Reliability: repeats and identifying random errorRead next10Accuracy vs precision (and how to improve both)Read next11Validity: controlling variables and fair testingRead next12Evaluating a method (limitations, improvements)Read next13Safe practical technique and risk control in chemistry contextsRead next
Using decimal numbers and standard form in chemistry contexts
1Using decimal numbers and standard form in chemistry contextsRead next2Ratios, fractions and percentages in chemistry problems (yield, composition)Read next3Using appropriate significant figuresRead next4Using means/averages for repeated measurementsRead next5Bar charts and frequency representations for dataRead next6Scatter graphs to identify patterns and trendsRead next7Changing the subject of an equation (e.g. Q = mcΔT, concentration equations)Read next8Substituting values with correct unitsRead next9Solving simple equations for unknownsRead next10Finding gradient and intercept from linear graphsRead next11Using a tangent to estimate rate of change on a curveRead next12Estimating area under a curve by counting squaresRead next
Thermal decomposition of different carbonates (compare ease)
1Thermal decomposition of different carbonates (compare ease)Read next2Comparing energy released by different fuels (temperature rise)Read next3Burning candles: air used up and products formedRead next4Calcium compounds: CaCO₃ decomposition; CaO + water; CaCO₃ + acidRead next5Neutralisation reactions using oxides/hydroxides/carbonatesRead next6Electrolysis of seawater or acidified waterRead next7Investigating rusting of iron (variables and prevention)Read next8Oxidation/reduction in combustion and competition reactionsRead next9Fractional distillation of synthetic crude oil (fractions + properties)Read next10Cracking paraffin oilRead next11Testing precipitate predictions when mixing soluble saltsRead next12Ion tests to identify unknown compoundsRead next13Heating a hydrated salt to find water of crystallisationRead next