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Chemistry
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Protons, neutrons and electrons: relative charge and relative massIsotopes and why they existWriting nuclide notation and working out numbers of subatomic particlesMeaning of relative atomic mass (Ar) and relative isotopic massCalculating Ar from isotopic abundance dataMass spectrometer basics: vaporisation, ionisation, acceleration, detectionInterpreting mass spectra: m/z peaks, molecular ion peakElectron shells and subshells (s, p, d) as energy levelsOrbitals as regions of electron probabilityElectron configurations for atoms and ions (including exceptions)First ionisation energy: definition and unitsTrends in first ionisation energy across a periodSuccessive ionisation energies and what they reveal about shellsExplaining IE anomalies: subshells, shielding, electron pairing
The mole as Avogadro’s number of particlesConverting between moles, mass and molar massEmpirical formula from percentage compositionMolecular formula from empirical formula and MrWriting balanced equations for calculationsUsing stoichiometric ratios to calculate reacting massesLimiting reagent problemsCalculating theoretical yieldPercentage yield calculationsAtom economy and why it matters (efficiency and waste)Concentration in mol dm⁻³ and converting volume units (cm³ ↔ dm³)Using c = n/V for solution calculationsGas volume at RTP (24.0 dm³ mol⁻¹): when it appliesTitration calculations: mean titre and moles at equivalence
Ionic bonding as electrostatic attraction in a latticeCovalent bonding as shared pairs of electronsDative (coordinate) bonding: what it is and how to draw itMetallic bonding: positive ions in a sea of delocalised electronsElectronegativity and what affects itBond polarity and dipoles from electronegativity differencesIntermolecular forces: London, permanent dipole-dipole, hydrogen bondingComparing intermolecular forces using boiling point dataShapes of molecules and ions using electron pair repulsion (VSEPR)Bond angles: predicting and explaining deviationsMeaning of oxidation state and how to calculate itIonic lattices vs molecular vs giant covalent vs metallic structuresLinking structure and bonding to melting point, conductivity, solubility
Endothermic vs exothermic reactions (energy profile diagrams)Enthalpy change (ΔH) and standard conditionsStandard enthalpy of combustion: definition and conventionsStandard enthalpy of formation: definition and conventionsUsing q = mcΔT in calorimetry calculationsConverting heat change to molar enthalpy changeCalorimetry errors and improvements: heat loss, incomplete combustion, insulationHess’s law as an energy cycle principleHess cycles using formation enthalpiesHess cycles using combustion enthalpiesMean bond enthalpy: meaning and limitationsCalculating ΔH from mean bond enthalpiesExplaining differences between bond enthalpy and Hess results
What rate of reaction means (change in concentration per unit time)Collision theory: successful collisions and activation energyEnergy profile diagrams for activation energyMaxwell–Boltzmann distribution: what the curve showsTemperature changes and Maxwell–Boltzmann explanation for rate increaseConcentration changes and collision frequencyPressure changes for gases and collision frequencyCatalysts: alternative pathway and lower activation energyMaxwell–Boltzmann explanation for catalysis (more particles above Ea)Measuring rate using gas volume or mass loss methodsInterpreting concentration–time graphs and tangent gradientsChoosing a suitable method for a given reaction (practical constraints)
Dynamic equilibrium: forward and reverse rates equalWriting equilibrium expressions for KcUnits of Kc and when they matterCalculating Kc from equilibrium concentrationsUsing ICE tables to find equilibrium amountsHomogeneous vs heterogeneous equilibria (what appears in Kc)Le Chatelier: concentration changes and direction of shiftLe Chatelier: temperature changes and direction of shift (link to ΔH)Le Chatelier: pressure changes (gases only, moles of gas comparison)Catalysts and equilibrium position (what changes and what doesn’t)Interpreting equilibrium graphs (concentration vs time)Using Kc magnitude to comment on position of equilibrium
Oxidation and reduction in terms of oxidation statesOxidation and reduction in terms of electron transferAssigning oxidation states in molecules and ionsIdentifying oxidising agents and reducing agentsWriting half-equations for redox changesBalancing redox equations in acidic conditionsDisproportionation: recognising and explaining itRedox titration ideas (what the endpoint means)Linking redox to real systems (corrosion, bleaching, batteries)
Lattice enthalpy: formation vs dissociation definitionsBorn–Haber cycles: why we use themConstructing a Born–Haber cycle from given dataCalculating lattice enthalpy using a Born–Haber cycleFactors affecting lattice enthalpy (ionic charge and radius)Entropy (ΔS) as disorder and energy dispersalPredicting sign of ΔS from state changes and moles of gasGibbs free energy (ΔG) and feasibilityUsing ΔG = ΔH − TΔS for feasibility at a given temperatureTemperature dependence of feasibility (when reactions become feasible)Linking ΔG to equilibrium ideas (conceptual link)
Rate equation form: rate = k[A]^m[B]^nOrders of reaction: meaning of 0th, 1st and 2nd orderDetermining order from initial rate dataUsing rate equations to calculate kUnits of k from overall orderHow rate data can suggest steps in a mechanismArrhenius equation as a temperature–k relationshipUsing Arrhenius graphs (ln k vs 1/T) to find EaActivation energy from experimental rate constantsChoosing a plausible rate-determining step from ordersComparing catalysts using activation energy and rate data
When to use Kp instead of Kc (gases)Partial pressure and how to calculate itWriting Kp expressions using partial pressuresUnits of Kp and what they depend onCalculating Kp from equilibrium partial pressuresUsing total pressure + mole fractions to find partial pressuresLinking Kp magnitude to equilibrium positionHow temperature affects Kp (via ΔH and equilibrium shift)
Redox as electrode processes in cellsStandard electrode potential: what it representsStandard hydrogen electrode as a referenceWriting half-equations using IUPAC conventionsCell diagrams and conventional cell representationCalculating Ecell from standard electrode potentialsPredicting feasibility using Ecell (spontaneous vs non-spontaneous)Identifying which electrode is oxidation/reductionNon-standard conditions: why conditions matter (conceptual, no Nernst)Rechargeable vs non-rechargeable cells: what reversible meansFuel cells: hydrogen fuel cell electrode reactions (concept level)Commercial cells example (lithium cell) and what happens at each electrode
Brønsted–Lowry acids and bases: proton transferConjugate acid–base pairsStrong vs weak acids: what fully dissociated meanspH as a logarithmic measure: pH = −log10[H+]Converting between pH and [H+]Calculating pH of a strong acid from concentrationIonic product of water Kw and what it meansUsing Kw to find pH of strong basesKa for weak acids: what it representsCalculating pH of weak acids using Ka (approximation where valid)Buffer solutions: what they are and why they resist pH changeCalculating pH of acidic buffers (Ka + concentrations)Titration curves: strong/weak acid–base combinations and key features
Classifying elements as s, p, d and f blockPeriod 3 atomic radius trend: explanationPeriod 3 first ionisation energy trend: explanation (including anomalies)Period 3 melting point trend: structure and bonding explanationsMetallic → giant covalent → molecular transitions across Period 3Oxides across Period 3: linking structure to properties (overview)Using data tables to justify periodic trends in exam answersComparing explanations: shielding, nuclear charge, electron configuration
Group 2 physical trends: atomic radius and first ionisation energyGroup 2 melting points: structure and bonding explanationReactions with water: observations and equations (Mg → Ba)Hydroxides: solubility trend and pH implicationsSulfates: solubility trend and applicationsThermal stability of carbonates and nitrates (trend + explanation)Uses of Group 2 compounds in medicine and agricultureMagnesium in the extraction of titanium (why Mg works)
Halogen electronegativity trend and implicationsHalogen boiling point trend: London forces explanationOxidising ability trend down Group 7Halogen displacement reactions in aqueous solutionHalide ions as reducing agents: trend and reasoningChlorine with water: formation of Cl− and ClO− (equation and meaning)Chlorine in water treatment: benefits and risks (balanced judgement)Halide tests with silver nitrate and ammonia (observations + equations)
Reactions of sodium and magnesium with water: comparing behaviourOxides across Period 3: basic to acidic trendOxides reacting with water: predicting pH of resulting solutionsAluminium oxide as amphoteric: reactions with acids and basesChlorides across Period 3: ionic vs covalent characterHydrolysis of chlorides (eg AlCl3, PCl5) and pH effectsExplaining trends using electronegativity and polarisationWriting equations for key oxide and chloride reactions
What makes a transition metal (incomplete d subshell in ions)Complex ions: central metal ion + ligandsLigands as lone pair donors (coordinate bonding)Substitution reactions: ligand exchange with H2O, NH3, Cl−Shapes of complexes: octahedral vs tetrahedralCis–trans isomerism in octahedral complexesOptical isomerism with bidentate ligands (concept and drawings)Why transition metal compounds are coloured (d–d transitions)Factors changing colour: oxidation state, ligand, coordination numberColorimetry: absorbance to find concentration (calibration curve)Variable oxidation states: vanadium redox changes in solutionTransition metals as catalysts: heterogeneous vs homogeneousCatalyst supports: surface area and cost arguments
Precipitation reactions as ionic tests (what a precipitate shows)Testing cations: Group 2 hydroxide precipitates (observations)Testing ammonium ions with NaOH and warming (ammonia test)Testing halide ions with AgNO3 and NH3 (confirmatory tests)Testing carbonate ions (CO2 test with acid + limewater)Testing sulfate ions (Ba2+ test and insoluble BaSO4)Using ionic equations for precipitation testsUsing observations to identify unknown ions (structured approach)Avoiding test interference and improving reliability (washing, controls)
Different ways to represent organic compounds (empirical → skeletal)Homologous series and functional groupsNaming alkanes, alkenes, halogenoalkanes, alcohols (IUPAC basics)Structural isomerism: chain, position and functional group isomersReaction mechanisms: why we use curly arrowsHeterolytic vs homolytic bond fissionElectrophiles and nucleophiles: recognising and describing themFree-radical substitution: overview and key featuresNucleophilic substitution: overview and key featuresElectrophilic addition: overview and key featuresOxidation reactions in organic chemistry (overview)Links: conditions, reagents and functional group change
Alkanes as saturated hydrocarbons and general formulaTrends in boiling point with chain length (London forces)Fractional distillation of crude oil (principle and fractions)Cracking: why it’s needed and what it producesCatalytic cracking vs steam cracking (conditions and products)Combustion of alkanes: complete vs incompleteCarbon monoxide and soot: conditions and hazardsFree-radical substitution with halogens: overall reactionInitiation, propagation and termination stepsExplaining product mixtures in radical substitutionWriting mechanisms with curly arrows (radical fishhooks)Ozone depletion and CFCs: radical chain reactions (conceptual)
Naming halogenoalkanes (primary, secondary, tertiary)Carbon–halogen bond polarity and its consequencesNucleophilic substitution with OH− to form alcoholsNucleophilic substitution with CN− to form nitriles (chain lengthening)Nucleophilic substitution with NH3 to form amines (introduction)Comparing rates: iodo > bromo > chloro (bond enthalpy)Primary vs tertiary: mechanism choice (SN2 vs SN1 idea level)Hydrolysis practical: ethanol and heating under refluxElimination to form alkenes (conditions and competing reactions)Equations for substitution and eliminationUsing IR to spot halogenoalkane functional features (link lesson)
Alkenes as unsaturated hydrocarbons and general formulaE/Z isomerism: why restricted rotation mattersAssigning E and Z using CIP priority rules (step-by-step)Electrophilic addition: how the double bond reactsReaction with Br2: bromine water test and mechanism ideaReaction with HX (eg HBr): products and mechanism ideaMarkovnikov’s rule: predicting the major product (where relevant)Addition polymerisation: turning alkenes into polymersConditions for polymerisation (general)Comparing addition vs condensation polymerisation (preview)Using alkenes as chemical feedstocks (context lesson)
Naming alcohols and classifying as primary/secondary/tertiaryAlcohol intermolecular forces and boiling point trendsEthanol production by fermentation: conditions and limitationsEthanol production by hydration of ethene: conditions and catalystsComparing fermentation vs hydration (rate, purity, sustainability)Oxidation of primary alcohols to aldehydes (conditions)Oxidation of primary alcohols to carboxylic acids (conditions)Oxidation of secondary alcohols to ketones (conditions)Why tertiary alcohols resist oxidation (structure explanation)Dehydration of alcohols to alkenes (elimination conditions)Substitution of alcohols to halogenoalkanes (overview)Choosing reagents and conditions from functional group targets
Combustion analysis: CO2 and H2O data to find empirical formulaMass spectrometry: molecular ion and fragmentationInterpreting mass spectra for simple organic fragmentsInfrared (IR) spectroscopy: what bonds absorb IR and whyRecognising key IR absorptions (O–H, C=O, C–H, N–H)Using IR to distinguish functional groups in unknownsUsing multiple techniques together (MS + IR + chemical tests)Writing a logical identification sequence for exam questions
What makes a chiral centre (four different groups)Enantiomers as non-superimposable mirror imagesDrawing 3D representations (wedge/dash)Optical activity and plane-polarised lightRacemic mixtures and why they’re optically inactive overallBiological significance of enantiomers (drugs and receptors)Distinguishing enantiomers, structural isomers, E/Z isomersExam technique: spotting chirality quickly in skeletal structures
Naming aldehydes and ketonesCarbonyl group: polarity and nucleophilic addition (overview)Oxidation of alcohols revisited (making aldehydes/ketones)Tollens’ test for aldehydes: observations and explanationFehling’s/Benedict’s test: observations and explanationWhy ketones don’t react in these oxidation testsReduction of carbonyls to alcohols (NaBH4 / LiAlH4 idea level)2,4-DNP test for carbonyls: observations and purposeDistinguishing aldehydes, ketones and alcohols using tests
Naming carboxylic acids and recognising acidity trendsCarboxylic acid strength vs alcohols/phenols (comparison lesson)Reactions with carbonates: CO2 test and equationsEsterification: making esters from acids and alcohols (conditions)Ester hydrolysis: acidic vs alkaline hydrolysis (differences)Acyl chlorides: why they are reactive (bond polarity)Acyl chloride reactions with water, alcohols and ammoniaAmides: formation from acyl chlorides and amines/ammoniaComparing reactivity: acyl chlorides vs esters vs carboxylic acids
Benzene structure: delocalised π system and stabilityEvidence for benzene’s structure (bond lengths and enthalpy ideas)Why benzene undergoes substitution not additionElectrophilic substitution: general mechanism outlineNitration of benzene: reagents, conditions and mechanism stepsHalogenation of benzene: catalyst role (AlCl3 / FeBr3)Friedel–Crafts acylation/alkylation (overview, catalysts)Directing effects with substituents (basic overview if taught)Using aromatic chemistry to build synthesis routes
Naming amines and classifying as primary/secondary/tertiaryAmines as bases: lone pair acceptance and pH effectsComparing basicity: aliphatic amines, ammonia, aromatic aminesMaking amines: reduction of nitriles (overview)Formation of amides from acyl chlorides + amines (link lesson)Diazotisation of aromatic amines (phenylamine): conditions (overview)Azo dyes: coupling reactions and coloured products (overview)Salt formation with acids: making ammonium saltsTest-tube observations suggesting an amine functional group
Addition polymerisation: repeating units from alkene monomersDrawing repeating units correctly from monomersPoly(alkenes) properties: chain length, branching, intermolecular forcesCondensation polymerisation: polymers + small molecule by-productPolyesters: formation from diols and dicarboxylic acidsPolyamides: formation from diamines and dicarboxylic acids/acyl chloridesIdentifying monomers from a polymer repeat unitPolymer disposal: recycling, biodegradability, incineration (balanced view)Biopolymers and sustainability (context lesson)
Amino acids as zwitterions: internal acid–base behaviourIsoelectric point and why charge changes with pHPeptide bond formation: condensation between amino acidsHydrolysis of peptides and proteins (acid/base/enzyme overview)Protein structure levels: primary → quaternary (concept lesson)Hydrogen bonding and shapes in proteins (concept lesson)DNA components: sugar, phosphate, basesBase pairing and hydrogen bonding in DNADNA as a condensation polymer (link lesson)Using chemistry to explain biological function (synoptic lesson)
Planning a synthesis: choosing functional group interconversionsWriting multi-step routes with correct reagents and conditionsHalogenoalkanes as starting points (substitution vs elimination choices)Alkenes as starting points (addition reactions to build complexity)Using oxidation and reduction strategically in routesProtecting group idea (concept-level awareness where relevant)Purification: recrystallisation vs distillation (when to use which)Calculating percentage yield in multi-step synthesisImproving yield and purity: drying, excess reagent, separationUsing IR/MS/NMR evidence to confirm products in a route
What NMR measures (hydrogen environments in ¹H NMR)Chemical shift (δ) and what influences itShielding and deshielding: electron density effectsSplitting patterns: the n+1 ruleInterpreting integration for relative numbers of H atomsUsing splitting, integration, shifts to propose structuresCommon ¹H NMR features (alkyl, aromatic, aldehyde, acid O–H)Combining NMR with IR/MS to identify unknowns
Chromatography as separation by partition between phasesStationary phase vs mobile phase (what each does)Thin-layer chromatography (TLC): setup and how to run itCalculating Rf values and interpreting themUsing TLC to assess purity and reaction progressGas chromatography (GC): separation by volatility and interactionsRetention time and what affects itUsing chromatography with mass spectrometry (GC-MS concept)Choosing the right chromatography method for a scenario
Safe handling of chemicals and interpreting hazard informationRecording measurements correctly (mass, time, volume, temperature)Using volumetric apparatus accurately (pipette, burette, volumetric flask)Planning variables: independent, dependent and control variablesPresenting data in tables with correct headings and unitsGraph skills: axes, plotting points, best-fit curvesDetermining gradient (including tangents) and what it meansUncertainty, accuracy and precision: what each term meansIdentifying sources of systematic and random errorEvaluating methods and suggesting realistic improvementsUsing pH meters/probes and calibrating where appropriateMeeting CPAC expectations through consistent lab practice
Make a volumetric solution and carry out a simple acid–base titrationMeasure an enthalpy change (calorimetry)Investigate how rate changes with temperatureIdentify cations/anions by test-tube reactions (Group 2, NH4+, halides, OH−, CO3^2−, SO4^2−)Distil a product from a reactionTest for alcohol, aldehyde, alkene and carboxylic acid functional groupsMeasure rate by initial-rate method and by continuous monitoringMeasure the EMF of an electrochemical cellInvestigate pH change in weak acid–strong base and strong acid–weak base reactionsPrepare a pure organic solid/liquid and test purityIdentify transition metal ions by test-tube reactionsSeparate species by thin-layer chromatography (TLC)
