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GCSEOCR
Chemistry
Exam Questions
Solids, liquids and gases in the particle modelNewParticle arrangement, movement and energy in each stateNewMelting and freezing explained by particlesNewBoiling and condensing explained by particlesNewSublimation and deposition explained by particlesNewChanges of state are physical and reversibleNewDiffusion in gases using the particle modelNewDiffusion in liquids using the particle modelNewExplaining gas pressure using particle collisionsNewPhysical changes vs chemical changes (particle-level view)NewWhy the “hard sphere” particle model has limitationsNewParticle model limitations: forces, spacing and particle sizeNew
Dalton’s atomic modelNewThomson’s plum pudding modelNewRutherford/Geiger–Marsden alpha scattering experimentNewThe nuclear model: what it explained and what it didn’tNewBohr’s electron shell modelNewWhy atomic models change over time (evidence and revision)NewNucleus vs electron cloud: where mass and charge areNewOrders of magnitude: typical atom size (10⁻¹⁰ m)NewProton, neutron, electron: charges and relative massesNewAtomic number and mass numberNewIsotopes and isotope notationNewCalculating protons, neutrons and electrons in atomsNewIons: what changes when ions formNewCalculating protons, neutrons and electrons in ionsNew
“Pure” in chemistry vs “pure” in everyday languageNewElements, compounds and mixtures: what counts as pureNewUsing melting point to identify purityNewWhy impurities change melting point (range + lower mp)NewRelative atomic, molecular and formula massNewCalculating relative formula mass from a formulaNewUsing relative masses inside balanced equationsNewEmpirical formula from atom ratiosNewEmpirical formula from models/diagramsNewFormulations as useful mixturesNewAlloys as formulations (why alloys are useful)NewFiltration: separating insoluble solids from liquidsNewCrystallisation: making a solid from solutionNewSimple distillation: separating a solvent from a solutionNewFractional distillation: separating liquids with different boiling pointsNewChoosing separation methods from substance propertiesNewPaper chromatography: setup and how separation happensNewTLC chromatography: setup and spottingNewMobile phase vs stationary phaseNewInterpreting a chromatogram (spots, components)NewCalculating and comparing Rf valuesNewUsing chromatography to test purityNewChoosing chromatography methods (paper/TLC/gas) for contextNew
Metals vs non-metals: key physical propertiesNewMetals vs non-metals: chemical behaviour (ions/oxides)NewElectron shells and the periodic table (group/period meaning)NewAtomic number and electron arrangement linkNewIonic bonding: electron transfer and ion formationNewIonic lattices: why ionic compounds aren’t “molecules”NewCovalent bonding: sharing electrons in moleculesNewMetallic bonding: positive ions and delocalised electronsNewPolymers as giant molecules (repeat units idea)NewGiant covalent vs simple molecular substancesNewDot-and-cross diagrams for simple covalent moleculesNewDot-and-cross diagrams for binary ionic compoundsNewFrom ion charges to ionic formulae (criss-cross method)NewComparing bonding/structure types across substancesNewRepresentations and models: strengths and limitationsNew2D vs 3D structures (why shape matters)NewMendeleev’s table: what he got right (patterns)NewModern periodic table: why atomic number mattersNew
Carbon’s four covalent bonds: why it mattersNewCarbon chains and rings: many organic compoundsNewDiamond structure and key propertiesNewGraphite structure and key propertiesNewGraphene structure and key propertiesNewFullerenes structure and key propertiesNewBond strength vs intermolecular forces (what each controls)NewExplaining mp/bp using bonds and intermolecular forcesNewUsing data to predict state at given conditionsNewIonic solids: structure and properties (mp, conductivity)NewSimple molecular substances: structure and propertiesNewGiant covalent substances: structure and propertiesNewMetals: structure and properties (conductivity, malleability)NewPolymers: structure and properties (flexibility, melting range)NewNanoparticles: size and scale (standard form focus)NewSurface area to volume ratio at the nanoscaleNewUses of nanoparticles (properties-led examples)NewRisks/uncertainties of nanoparticles (size changes behaviour)New
Using symbols to write formulae for elementsNewWriting formulae for simple covalent compoundsNewWriting formulae for ionic compounds (from charges)NewWriting balanced symbol equations from word equationsNewUsing conservation of mass to balance equationsNewState symbols: (s), (l), (g), (aq)NewHalf equations: what they representNewWriting half equations for simple processesNewCommon ions: recognising and using ion formulaeNewDeducing compound formulae from ions in a questionNewWriting balanced ionic equations (cancel spectator ions)NewAvogadro constant: meaning (standard form)NewThe mole: what it measuresNewConverting mass to moles (and back)NewConservation of mass in reactionsNewExplaining mass change in open systems (gas exchange)NewStoichiometry from a balanced equation (mole ratio)NewLimiting reactant: identifying what runs out firstNewCalculating masses from equationsNew
Exothermic reactions: temperature rise of surroundingsNewEndothermic reactions: temperature fall of surroundingsNewEnergy transfer vs “energy used up” (correct language)NewReaction profiles: exothermic vs endothermicNewActivation energy on a reaction profileNewBond breaking needs energy (endothermic step)NewBond making releases energy (exothermic step)NewOverall energy change: making minus breakingNewBond energy calculations for reaction energy change (Higher)NewComparing reactions using reaction profilesNew
Oxidation and reduction in terms of oxygenNewIdentifying oxidised and reduced species (oxygen definition)NewOxidising agents and reducing agents (oxygen definition)NewOxidation and reduction in terms of electronsNewIdentifying oxidised and reduced species (electron definition)NewAcids in water: hydrogen ionsNewAlkalis in water: hydroxide ionsNewNeutralisation: acid + alkali/base → salt + waterNewIonic equation for neutralisation: H⁺ + OH⁻ → H₂ONewAcids + metals: predicting products and balancing equationsNewAcids + carbonates: predicting products and balancing equationsNewConcentrated vs dilute acids (amount per volume)NewStrong vs weak acids (degree of ionisation)NewpH scale: what it measuresNewNeutrality, acidity and alkalinity (whole-number pH)NewpH and [H⁺]: factor of ten ruleNewMeasuring pH with indicators (universal indicator)NewMeasuring pH with a pH probe/meterNew
Electrolytes, ions, and why ionic liquids conductNewCations and anions: direction of movementNewCathode and anode: identifying each electrodeNewProducts with inert electrodes (metals/H₂ at cathode; non-metals at anode)NewMolten binary ionic electrolysis: predicting productsNewAqueous electrolysis: competing species ideaNewProducts for aqueous NaCl (brine) electrolysisNewProducts for aqueous CuSO₄ electrolysis (inert electrodes)NewExplaining products using ions present and discharge competitionNewWriting half equations for electrode reactionsNewElectrolysis and redox (electron gain/loss at electrodes)New
Group 1: key physical and chemical propertiesNewGroup 1 trends down the group (reactivity pattern)NewGroup 7: key physical and chemical propertiesNewGroup 7 trends down the group (reactivity pattern)NewGroup 0: key physical and chemical properties (inert behaviour)NewGroup 0 trends down the group (bp/density patterns)NewExplaining group trends using outer-shell electronsNewTransition metals: general properties (density, mp, reactivity)NewTransition metal ions: coloured compounds and variable chargesNewTransition metals as catalysts (why useful)NewPredicting reactivity from periodic table positionNewMetal + water reactions: patterns and predictionsNewMetal + dilute acid reactions: patterns and predictionsNewReactivity series: what it is and how it’s usedNewDisplacement reactions between metals and metal saltsNewUsing experiments to deduce metal reactivity orderNew
Testing oxygen (positive test + why it works)NewTesting hydrogen (positive test + why it works)NewTesting carbon dioxide (positive test + why it works)NewTesting chlorine (positive test + why it works)NewTesting carbonate ions (acid test + CO₂ confirmation)NewHalide tests with silver nitrate (Cl⁻, Br⁻, I⁻)NewSulfate test with barium ionsNewNaOH cation tests: calciumNewNaOH cation tests: copperNewNaOH cation tests: iron(II)NewNaOH cation tests: iron(III)NewNaOH cation tests: zinc (including solubility points)NewFlame tests: method and safetyNewFlame colours: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺NewIdentifying unknowns from multiple test resultsNewInstrumental methods: speed, accuracy, sensitivityNewInterpreting instrumental results using referencesNewReading simple mass spectrometry-style charts (pattern matching)New
Concentration in mol/dm³: what it meansNewCalculating mol/dm³ from mass, formula mass, and volumeNewConverting volume units (cm³ ↔ dm³)NewConcentration in g/dm³: meaning and useNewPreparing a standard solution (core technique)NewTitration apparatus and setup (burette, pipette, indicator)NewIdentifying the end point (colour change judgement)NewTitration calculations using mole ratiosNewGas moles and gas volume relationshipNewMolar gas volume at RTP (24 dm³): correct useNewCalculating gas volumes from a balanced equationNewTheoretical yield from reactant massNewActual yield vs theoretical yieldNewPercentage yield calculationsNewAtom economy: definitionNewAtom economy calculations from equationsNewChoosing pathways using data (yield, atom economy, rate, eqm, by-products)New
Rate of reaction: what it measuresNewCollision theory basics (frequency and energy)NewMeasuring rate by gas volume collectedNewMeasuring rate by mass lossNewMeasuring rate by precipitation (visibility)NewMeasuring rate by colour change/timeNewPlotting rate graphs correctly (units and axes)NewInterpreting rate graphs (steepness and completion)NewMean rate over an intervalNewInstantaneous rate using tangents/gradients (Higher)NewEffect of concentration on rate (collision theory)NewEffect of temperature on rate (collision theory)NewEffect of surface area on rate (collision theory)NewEffect of pressure on gas reactions (collision theory)NewCatalysts: what they do and don’t doNewCatalysts and activation energy (reaction profile view)NewDesigning a fair test for rate (controls and repeats)New
Reversible reactions: symbol and meaningNewClosed systems and why they matter for equilibriumNewDynamic equilibrium: forward rate equals reverse rateNewLe Chatelier: changing concentrationNewLe Chatelier: changing temperatureNewLe Chatelier: changing pressure (gas equilibria)NewUsing equilibrium shifts to increase yieldNew“Best conditions” problems: yield vs rate vs cost trade-offsNew
Using carbon to extract metals (reduction of oxides)NewExtracting iron: principles (carbon in reactivity series)NewExtracting non-ferrous metals by reduction (principles + example)NewWhy some metals must be extracted by electrolysisNewElectrolysis extraction: basic industrial principlesNewBioleaching: how bacteria help metal extractionNewPhytomining: using plants to accumulate metalsNewComparing biological and traditional extraction methodsNewHaber process: reactants and productsNewHaber process: catalyst and conditionsNewHaber process: equilibrium (yield vs rate trade-off)NewWhy the Haber process matters for food productionNewNPK fertilisers: what N, P and K do for cropsNewFertiliser production as integrated industrial processesNewMaking fertilisers in lab vs industryNewContact process: why we make sulfuric acidNewContact process: steps, catalyst and conditionsNewContact process: equilibrium (yield vs rate trade-off)NewGraphs of conditions vs rate (industry context)NewChoosing industrial conditions using cost, energy, eqm and rateNewLife-cycle assessment: included stagesNewUsing LCA data to make a judgementNewRecycling for a different use (why viable)NewFactors affecting recycling decisions (economic + environmental)NewKey alloys: steel, brass, bronze, solder, duraluminNewCorrosion: what it is and when it happensNewRusting conditions for iron (water + oxygen)NewPreventing corrosion using barriers (paint/oil/plastic)NewPreventing corrosion using galvanising/platingNewPreventing corrosion using sacrificial protectionNew
Functional groups: spotting in structuresNewHomologous series: what makes a familyNewAlkanes: names and displayed structures (first four)NewAlkenes: names and displayed structures (first four)NewAlcohols: names and displayed structures (first four)NewCarboxylic acids: names and displayed structures (first four)NewPredicting formulas/structures in a homologous seriesNewHydrocarbon combustion: products and equationsNewBromine test for alkenes (addition across C=C)NewHydrogenation of alkenes (addition across C=C)NewOxidising alcohols to carboxylic acids (KMnO₄ idea)NewAddition polymerisation: monomer to polymer (repeat units)NewDrawing repeat units with [ ]ₙ notationNewDeducing the monomer from an addition polymerNewCondensation polymerisation: small molecule lossNewPolyesters and polyamides as condensation polymers (block diagrams)NewMaking condensation polymer in lab (e.g. nylon practical)NewDNA: polymer of nucleotides (names of nucleotides)NewNatural polymers: sugars and amino acids (examples)NewFunctional groups: why reactions can be predictedNewFractional distillation of crude oil: how it worksNewNaming crude oil fractions (core set)NewFraction boiling points: size + intermolecular forcesNewCrude oil fractions as alkane mixtures (CnH2n+2)NewCrude oil as finite petrochemical feedstockNewModern dependence on hydrocarbons (case examples)NewCracking: why we do it (demand vs supply)NewCracking conditions (overview)NewUseful cracking products (alkenes and fuels)NewChemical cells: why they produce a potential differenceNewHydrogen–oxygen fuel cell chemistry (overall reaction)NewFuel cells: pros and cons for given usesNew
Evidence for early atmosphere formationNewHow atmospheric composition changed over timeNewHow an oxygen-rich atmosphere developedNewGreenhouse effect: radiation interacting with atmosphereNewEvidence for human causes of climate change (correlations)NewUncertainties in climate evidence (meaning of uncertainty)NewEffects of increased CO₂ and CH₄ on climateNewMitigating climate change (strategies and trade-offs)NewMajor CO sources and why CO is harmfulNewMajor SO₂ sources and why SO₂ is harmfulNewMajor NOx sources and why NOx are harmfulNewParticulates: sources and health/environment effectsNewPotable water: meaningNewFresh water treatment (filtration/chlorination overview)NewTreating wastewater: what needs removingNewDesalination: technique and energy/cost trade-offsNew
Lab safety basics: hazards, risks and control measuresNewWriting a simple method that controls variablesNewVariables: independent, dependent, controlNewAccuracy, precision, repeatability, reproducibilityNewRecording results in tables with correct unitsNewChoosing equipment to reduce uncertaintyNewDrawing and interpreting line graphs for chemistry dataNewCalculating gradients and using them as ratesNewSignificant figures in chemistry calculationsNewScientific diagrams: clear apparatusNew
