GCSE Chemistry

• Ionic bonding, structure and properties

  ≈ 3%1 h 30 min

  This topic covers how ionic bonds form by electron transfer between metals and non-metals, and how the resulting giant ionic lattice explains the physical properties of ionic substances. Exams test dot-and-cross diagrams, formula writing, bonding explanations and application of structure-property ideas to melting point, conductivity and solubility contexts.

  • describe ionic bonding as the electrostatic attraction between oppositely charged ions formed by electron transfer
  • represent the formation of simple positive and negative ions, including by using electron-shell or dot-and-cross diagrams
  • deduce and write the formulae of ionic compounds from the charges on ions
  • describe the structure of ionic compounds as regular giant ionic lattices of alternating positive and negative ions
  • explain the properties of ionic compounds in terms of ionic bonding and giant ionic structure, including high melting and boiling points and electrical conductivity when molten or dissolved but not when solid
  • apply knowledge of ion charges and ionic structure to unfamiliar examples and compare ionic substances with simple molecular or metallic substances where required

• Covalent bonding and intermolecular forces

  ≈ 3%1 h 45 min

  This topic covers covalent bonding in simple molecules, the meaning of shared pairs of electrons, and the intermolecular forces that act between molecules. Exams test bonding diagrams, explanations of molecular properties and comparisons between covalent substances with weak intermolecular forces and substances with stronger bonding throughout the structure.

  • describe covalent bonding as the sharing of pairs of electrons between non-metal atoms
  • draw and interpret dot-and-cross diagrams or displayed structures for simple covalent molecules
  • describe the structure of simple molecular substances as molecules held together by strong covalent bonds, with weak intermolecular forces between molecules
  • explain the low melting and boiling points of simple molecular substances in terms of weak intermolecular forces, despite strong covalent bonds within molecules
  • explain why simple covalent substances do not conduct electricity because they have no ions or delocalised electrons
  • apply ideas about intermolecular forces to states of matter and volatility for simple molecular substances

• Giant covalent and metallic structures

  ≈ 3%1 h 30 min

  This topic covers giant covalent structures such as diamond, graphite, graphene and silicon dioxide, and metallic bonding in metals and alloys. Exams test structure-property explanations, use of key examples and comparison of how bonding determines hardness, melting point, conductivity and malleability.

  • describe giant covalent structures as networks of atoms joined by many strong covalent bonds
  • explain the properties of diamond, graphite, graphene and silicon dioxide in terms of their bonding and structure
  • compare diamond and graphite, including hardness, electrical conductivity and uses
  • describe metallic bonding as the electrostatic attraction between positive metal ions and delocalised electrons
  • explain the typical properties of metals and alloys, including electrical and thermal conductivity, high melting point, strength and malleability, in terms of metallic bonding
  • apply bonding and structure ideas to explain why alloys are harder than pure metals and to predict properties of unfamiliar giant covalent or metallic substances

• States of matter, kinetic theory and gas behaviour

  ≈ 2%1 h 15 min

  This topic covers the particle model of solids, liquids and gases, changes of state, and how kinetic theory explains pressure and gas behaviour. Exams test particle-level explanations, interpretation of state changes and the use of gas-pressure ideas, including the effect of temperature in a fixed volume.

  • describe the arrangement, movement and relative energy of particles in solids, liquids and gases
  • explain changes of state in terms of energy transfers and changes in particle motion, including melting, freezing, boiling, condensing and sublimation where specified
  • use kinetic theory to explain gas pressure as the result of particles colliding with the walls of a container
  • explain the effect of temperature on the pressure of a fixed mass of gas at constant volume in terms of particle kinetic energy and collision frequency
  • interpret diagrams, graphs or practical situations involving changes of state, heating and cooling, or gas pressure
  • apply the particle model to explain diffusion in gases and liquids where required by the specification

• Advanced materials: alloys, ceramics, composites and nanoparticles

  ≈ 1%1 h

  AQA onlyPearson Edexcel onlyOCR Chemistry A (Gateway) onlyOCR Chemistry B (Twenty First Century) onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA onlyEdexcel International GCSE Chemistry only

  This topic covers how the properties of alloys, ceramics, polymers, composites and nanoparticles arise from their structure and composition, together with uses, benefits and possible risks of nanomaterials. Exams test comparison, evaluation and application of material choice to practical contexts.

  • describe alloys as mixtures containing a metal and at least one other element, and explain why their different-sized atoms can make them harder than pure metals

About 7 h of study, lessons and core practice

• Relative formula mass and the mole

  ≈ 3%1 h 45 min

  This topic covers relative atomic mass, relative formula mass and the mole as the unit for amount of substance. Exams test definitions, use of chemical formulae, and calculations linking mass, moles and numbers of particles.

  • define relative atomic mass ($A_r$) and relative formula mass ($M_r$) and calculate $M_r$ from a chemical formula using given atomic masses
  • define the mole as the amount of substance containing the Avogadro constant number of entities and use $N_A = 6.02 \times 10^{23}\ \text{mol}^{-1}$ where required
  • calculate the amount of substance in moles from mass and molar mass using $n = \dfrac{m}{M}$
  • calculate mass from amount of substance using $m = nM$
  • calculate the number of atoms, molecules, ions or formula units from moles, and calculate moles from a given number of particles
  • interpret chemical formulae in terms of numbers and ratios of atoms or ions present

• Balancing equations and stoichiometry

  ≈ 3%1 h 45 min

  This topic covers conservation of mass, balanced symbol equations and the quantitative meaning of stoichiometric coefficients. Exams test balancing equations and using mole ratios to calculate amounts of reactants and products.

  • write and balance symbol equations so that they conserve atoms and overall mass
  • explain that the coefficients in a balanced equation give the stoichiometric ratios of moles of reactants and products
  • use balanced equations to determine mole ratios between substances in a reaction
  • calculate the amount of one substance from the amount of another substance using stoichiometric relationships
  • interpret word equations, symbol equations and ionic equations quantitatively where these are within specification scope

• Empirical formulae, molecular formulae and percentage composition

  ≈ 2%1 h 30 min

  This topic covers composition calculations from formulae and experimental data, including empirical and molecular formulae. Exams test percentage composition, deriving simplest ratios, and using relative formula mass to find molecular formulae.

  • calculate the percentage by mass of an element in a compound from its chemical formula
  • calculate the percentage composition of a compound from experimental or compositional data
  • determine the empirical formula of a compound from masses or percentage compositions of its elements
  • determine the molecular formula from the empirical formula and the relative formula mass
  • explain the difference between an empirical formula and a molecular formula

• Reacting masses, limiting reactants, yield and atom economy

  ≈ 4%2 h

  This topic applies mole calculations to reacting quantities in real processes. Exams test reacting mass calculations, identification of the limiting reactant, percentage yield and atom economy, often in multistep written problems.

  • calculate the masses of reactants and products from balanced equations using moles and molar masses
  • identify the limiting reactant from quantities of reactants and use it to determine the maximum amount of product
  • calculate the theoretical yield from given amounts of reactants
  • calculate percentage yield using $\text{percentage yield} = \dfrac{\text{actual yield}}{\text{theoretical yield}} \times 100$
  • calculate atom economy using $\text{atom economy} = \dfrac{M_r\ \text{of desired product}}{\text{total } M_r\ \text{of products}} \times 100$
  • evaluate reactions and processes in terms of percentage yield, atom economy, waste minimisation and sustainable use of resources

• Concentration, titration and solution calculations

  ≈ 3%2 h

  This topic covers the quantitative treatment of solutions, including concentration and acid-alkali titration calculations. Exams test unit conversion, use of concentration equations, and determination of unknown concentrations from titres and balanced equations.

  • calculate concentration in $\text{mol dm}^{-3}$ using $c = \dfrac{n}{V}$ with volume in $\text{dm}^3$
  • convert volumes between $\text{cm}^3$ and $\text{dm}^3$ and use these units correctly in calculations
  • calculate the amount of solute in a given volume of solution and calculate required volume from concentration and moles
  • use the mean titre from concordant titration results where appropriate
  • calculate the concentration of an unknown solution from titration data and a balanced equation
  • apply stoichiometric ratios in solution calculations involving acids, alkalis and other soluble substances

• Gas volumes and gas stoichiometry

  ≈ 2%1 h 15 min

  This topic covers amounts of gases and their use in quantitative chemistry at room temperature and pressure or equivalent stated conditions. Exams test molar gas volume, conversion between moles and gas volume, and gas-volume stoichiometry from balanced equations.

  • state and use the molar volume of a gas at room temperature and pressure as approximately $24\ \text{dm}^3\ \text{mol}^{-1}$, or $24{,}000\ \text{cm}^3\ \text{mol}^{-1}$, where this convention is used
  • calculate gas volume from amount of substance and calculate amount of substance from gas volume
  • convert gas volumes between $\text{cm}^3$ and $\text{dm}^3$ in quantitative problems
  • use balanced equations to calculate the volumes of gaseous reactants and products
  • solve combined mass-mole-gas-volume problems involving gases in reactions

About 10 h 15 min of study, lessons and core practice

• Acids, alkalis, pH and neutralisation

  ≈ 3%1 h 30 min

  This topic covers the properties of acidic, alkaline and neutral substances, the pH scale, and neutralisation reactions. In exams, students are tested on interpreting indicator results, writing word and symbol equations, and explaining acidity and alkalinity using ions in solution.

  • describe the characteristic properties of acids and alkalis, including their effects on indicators and their reactions with metals, bases and carbonates
  • interpret and use the pH scale to classify substances as strongly acidic, weakly acidic, neutral, weakly alkaline or strongly alkaline
  • explain acidity and alkalinity in terms of the presence of $\text{H}^+(\text{aq})$ and $\text{OH}^-(\text{aq})$ ions
  • define an alkali as a soluble base and distinguish between acids, bases and alkalis using official terminology
  • write word equations and balanced symbol equations for neutralisation reactions, including acid + base, acid + alkali and acid + carbonate
  • explain that neutralisation produces a salt and water, and that acids reacting with carbonates also produce carbon dioxide

• Salts, solubility and preparation methods

  ≈ 2%1 h 30 min

  This topic covers how salts are named, how soluble and insoluble salts are prepared, and how crystallisation and precipitation are used in the laboratory. In exams, students are commonly asked to choose a suitable preparation method, sequence practical steps, and apply solubility rules.

  • name salts formed from hydrochloric acid, nitric acid and sulfuric acid as chlorides, nitrates and sulfates
  • select and explain a suitable method for preparing a soluble salt from an acid using an excess insoluble base, metal or carbonate
  • describe how to prepare a pure, dry soluble salt crystal by warming, reacting, filtering, evaporating and crystallising
  • describe how to prepare a soluble salt by acid-alkali titration when both reactants are soluble
  • use solubility rules to predict whether an ionic compound will dissolve in water or form a precipitate
  • describe and explain the preparation of an insoluble salt by precipitation from suitable soluble solutions, followed by filtration, washing and drying

• Redox, the reactivity series and displacement

  ≈ 4%1 h 45 min

  This topic covers oxidation, reduction and the ordering of metals by reactivity, together with reactions that compare their tendency to lose electrons. Exams test explanations of displacement reactions, interpretation of experimental evidence, and application of the reactivity series to predict products and methods.

  • define oxidation and reduction in terms of oxygen gain or loss and, where required, electron loss or gain
  • identify redox reactions and state which species is oxidised and which is reduced
  • recall and apply the reactivity series of metals and carbon to compare the reactivity of common metals
  • predict and explain the outcomes of reactions of metals with water, dilute acids and oxygen using the reactivity series
  • predict and explain displacement reactions involving metals and aqueous solutions of metal salts
  • interpret experimental observations to place metals in order of reactivity and to justify conclusions about relative reactivity

• Metal extraction, corrosion and recycling

  ≈ 3%1 h 30 min

  This topic covers how the position of a metal in the reactivity series determines its extraction method, and how metals corrode and can be protected or recycled. In exams, students apply reactivity ideas to extraction, explain rusting and prevention methods, and evaluate environmental and economic issues in recycling.

  • explain why unreactive metals can occur native but more reactive metals are found as compounds such as oxides
  • explain that metals less reactive than carbon can be extracted from their oxides by reduction with carbon or carbon monoxide
  • explain that metals more reactive than carbon are extracted by electrolysis of molten compounds
  • describe oxidation as the loss of electrons by metals during extraction and corrosion processes
  • describe rusting as the corrosion of iron and state that both oxygen and water are required
  • explain methods used to reduce corrosion and evaluate the advantages and disadvantages of recycling metals compared with extracting them from ores

• Electrolysis of molten and aqueous substances

  ≈ 4%2 h

  This topic covers the decomposition of ionic substances by electricity, including molten salts and aqueous solutions, and the movement and discharge of ions at electrodes. Exams commonly test half-equations, product prediction, and explanations based on ion charge, ion movement and relative reactivity.

  • define electrolysis as the decomposition of an ionic compound by the passage of electricity
  • describe the movement of cations to the cathode and anions to the anode in molten and aqueous electrolytes
  • explain why ionic compounds conduct electricity when molten or dissolved but not when solid
  • predict the products of electrolysis of molten ionic compounds and write balanced half-equations for the electrode reactions
  • predict the products of electrolysis of aqueous solutions using the rules for hydrogen, metals, halogens and oxygen at the electrodes
  • interpret electrode processes in terms of oxidation at the anode and reduction at the cathode

• Industrial electrolysis and electroplating

  ≈ 1%1 h

  This topic covers key applications of electrolysis, especially the chlor-alkali process and electroplating. In exams, students are expected to recall products and uses, explain the electrode reactions, and describe how electroplating transfers a metal coating from the anode or solution onto an object.

  • describe the electrolysis of concentrated sodium chloride solution (brine) and identify the products at each electrode and in the solution
  • write balanced half-equations and the overall equation for the electrolysis of brine
  • state important uses of chlorine, hydrogen and sodium hydroxide produced by the chlor-alkali process
  • describe electroplating as the use of electrolysis to coat an object with a thin layer of metal
  • explain the roles of the cathode, anode and electrolyte in electroplating and predict the direction of metal ion movement and deposition

About 9 h 15 min of study, lessons and core practice

• Exothermic and endothermic changes, including calorimetry

  ≈ 2.5%1 h 30 min

  This topic covers energy transfers in chemical reactions and changes of state, including the distinction between exothermic and endothermic processes and simple calorimetry calculations. Exams test recognition from descriptions, equations and temperature-change data, and may require evaluation of methods and sources of error in practical energy measurements.

  • distinguish between exothermic and endothermic changes in terms of energy transferred to or from the surroundings
  • identify exothermic and endothermic reactions and changes of state from observations, word equations, symbol equations and temperature-time data
  • explain the energy changes involved in breaking bonds and making bonds, and relate these to overall energy transfer in a reaction
  • measure temperature change in simple reaction or combustion calorimetry experiments and use the result to determine whether a process is exothermic or endothermic
  • calculate the energy transferred using $$E = mc\Delta T$$, using appropriate units and significant figures where required by the specification used
  • evaluate calorimetry methods by identifying heat loss, incomplete combustion, evaporation and measurement uncertainty as limitations, and suggest improvements such as insulation, lids and stirring

• Bond energies and reaction profiles

  ≈ 2%1 h 30 min

  AQA onlyPearson Edexcel onlyOCR Chemistry A (Gateway) onlyOCR Chemistry B (Twenty First Century) onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA onlyEdexcel International GCSE Chemistry only

  This topic covers reaction profiles, activation energy and bond energy calculations for chemical reactions. Exams test interpretation of energy level diagrams, links to catalyst action, and calculation or estimation of overall energy change from mean bond energies.

  • interpret reaction profile diagrams for exothermic and endothermic reactions, including the relative energies of reactants and products

• Rates of reaction, collision theory and measurement

  ≈ 3%1 h 45 min

  This topic covers what is meant by rate of reaction, how rate is measured, and how collision theory explains successful chemical change. Exams test interpretation of practical data, drawing and using rate graphs, and explaining rate in terms of collision frequency and energy.

  • define the rate of a chemical reaction in terms of the speed of disappearance of reactants or appearance of products
  • measure rate of reaction from practical observations such as gas volume produced, mass lost, precipitate formation or colour change
  • calculate mean rate from experimental data using change divided by time, with units appropriate to the quantity measured
  • plot and interpret graphs of quantity against time, including using tangents to estimate rate at a particular time where required
  • explain reactions in terms of collision theory, including that particles must collide and that only some collisions are successful
  • explain successful collisions in terms of particles colliding with sufficient energy and, where specified, the correct orientation

• Factors affecting rate and catalysis

  ≈ 2.5%1 h 30 min

  This topic covers the effects of concentration, pressure, surface area, temperature and catalysts on reaction rate. Exams test explanation using collision theory and particle ideas, interpretation of comparative data, and application to required practical contexts.

  • predict and explain the effect of changing concentration on the rate of a reaction in terms of collision frequency
  • predict and explain the effect of changing pressure on the rate of reactions involving gases in terms of particle spacing and collision frequency
  • predict and explain the effect of changing surface area of a solid on reaction rate in terms of exposed particles and frequency of collisions
  • predict and explain the effect of changing temperature on reaction rate in terms of particle kinetic energy, collision frequency and the greater proportion of particles with energy at least equal to the activation energy
  • describe what a catalyst does and explain that catalysts increase rate without being used up chemically in the overall reaction
  • interpret experimental results comparing rates under different conditions and evaluate the need to control variables for a fair test

• Reversible reactions, equilibrium and Haber conditions

  ≈ 2.5%1 h 45 min

  This topic covers reversible reactions, dynamic equilibrium and how conditions affect equilibrium position, with the Haber process as the main industrial application. Exams test symbolic representation, prediction of shifts using Le Chatelier’s principle, and evaluation of industrial conditions as compromises.

  • recognise and write reversible reactions using the reversible arrow and distinguish reversible from irreversible changes
  • describe dynamic equilibrium as a closed-system state in which the forward and reverse reactions continue at equal rates so the concentrations of reactants and products remain constant
  • predict the effect of changing concentration on the position of equilibrium using Le Chatelier’s principle
  • predict the effect of changing temperature on the position of equilibrium for exothermic and endothermic reversible reactions
  • predict the effect of changing pressure on the position of equilibrium in gaseous systems by considering the side with fewer or more moles of gas
  • explain and evaluate the conditions used in the Haber process, including temperature, pressure, iron catalyst and continuous removal of ammonia, as a compromise between rate, yield and cost

• Electrochemical cells, batteries and fuel cells

  ≈ 1.5%1 h 15 min

  AQA onlyPearson Edexcel onlyOCR Chemistry A (Gateway) onlyOCR Chemistry B (Twenty First Century) onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA onlyEdexcel International GCSE Chemistry only

  This topic covers cells that produce electricity from chemical reactions, including simple electrochemical cells, rechargeable and non-rechargeable batteries, and hydrogen fuel cells. Exams test comparison of devices, interpretation of half-cell or cell descriptions, and evaluation of advantages and disadvantages in practical use.

  • describe how a cell produces a potential difference from reactions involving two different electrodes and an electrolyte

About 9 h 15 min of study, lessons and core practice

• Group 1 and Group 7 chemistry

  ≈ 3%2 h

  This topic covers the characteristic physical and chemical properties of Group 1 alkali metals and Group 7 halogens, including trends down each group and halogen displacement reactions. Exams test explanation of trends using atomic structure, prediction of reactivity and observations, and application to unfamiliar examples and practical contexts.

  • describe the properties of Group 1 metals and explain their reactions with water, oxygen and chlorine in terms of electron loss and the formation of $+1$ ions
  • interpret and predict trends down Group 1 in reactivity, melting point and softness using atomic radius, shielding and attraction between the nucleus and the outer electron
  • describe the properties of Group 7 halogens and explain their simple molecular nature, diatomic formulae and coloured appearance or states at room temperature
  • interpret and predict trends down Group 7 in melting point, boiling point and reactivity using intermolecular forces and the gain of an electron into the outer shell
  • apply the concept of displacement to halogen reactions and write word or symbol equations for a more reactive halogen displacing a less reactive halide from solution
  • use simple oxidation state ideas and ionic equations to identify oxidation and reduction in halogen and halide reactions

• Group 0 and transition metals

  ≈ 2%1 h 15 min

  This topic covers the physical and chemical properties of the noble gases and transition metals, including trends in Group 0 and the typical features that distinguish transition elements from Group 1 metals. Exams test data interpretation, comparison of groups, and application of transition-metal properties to catalysis and everyday uses.

  • describe the properties of Group 0 noble gases as unreactive, monatomic gases with very low boiling points and explain their lack of reactivity in terms of full outer electron shells
  • interpret and predict the trend in boiling point down Group 0 using increasing atomic size and stronger intermolecular attractions
  • identify transition metals as elements that form at least one stable ion with an incomplete outer shell and distinguish them from Group 1 metals by their typical properties
  • describe the typical physical properties of transition metals, including high density, high melting point, strength, hardness and good electrical and thermal conductivity
  • describe the typical chemical properties of transition metals, including lower reactivity than Group 1 metals, formation of coloured compounds, catalytic activity and variable oxidation states

• Thermal decomposition, carbonates and the limestone cycle

  ≈ 2%1 h 30 min

  This topic covers the thermal decomposition of metal carbonates, the chemistry and uses of limestone, quicklime, slaked lime and limewater, and the limestone cycle. Exams test recall of key reactions, construction of symbol equations, interpretation of industrial and environmental contexts, and explanation of decomposition patterns.

  • describe thermal decomposition as the breakdown of a compound by heating and apply it to the decomposition of metal carbonates to metal oxides and carbon dioxide
  • write balanced symbol equations for the thermal decomposition of carbonates and for the reactions in the limestone cycle
  • describe limestone as mainly calcium carbonate and state its uses, including building material, manufacture of lime and neutralisation of acidic soils or industrial waste gases where specified
  • explain the conversion of calcium carbonate to calcium oxide and then to calcium hydroxide, and describe the use of limewater to test for carbon dioxide
  • interpret the limestone cycle as a sequence of reversible chemical changes between calcium carbonate, calcium oxide and calcium hydroxide

• Ammonia, the Haber process and fertilisers

  ≈ 1.5%1 h 15 min

  This topic covers ammonia production by the Haber process, the compromise conditions used in industry, and the manufacture and use of fertilisers. Exams test equilibrium reasoning, interpretation of reaction conditions, percentage-yield style ideas in context, and applied knowledge of NPK fertilisers and ammonium salts.

  • describe the Haber process as the reversible reaction of nitrogen with hydrogen to form ammonia and write the balanced symbol equation $$\mathrm{N_2 + 3H_2 \rightleftharpoons 2NH_3}$$
  • explain how temperature, pressure and the iron catalyst affect the rate and equilibrium position in the Haber process and justify the use of compromise industrial conditions
  • interpret the raw materials for ammonia manufacture, including nitrogen from air and hydrogen from natural gas or other sources, and relate this to cost and sustainability issues where required
  • describe ammonia as a feedstock for fertiliser production and identify fertilisers that supply nitrogen, phosphorus and potassium to improve plant growth
  • describe how ammonium salts are produced by reacting ammonia with acids and apply this to named examples such as ammonium sulfate or ammonium nitrate

• Sulfuric acid and the Contact process

  ≈ <1%45 min

  Cambridge IGCSE Chemistry onlyCambridge IGCSE (9-1) Chemistry onlyEdexcel International GCSE Chemistry onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA only

  This topic covers the stages of the Contact process and the manufacture and uses of sulfuric acid. Exams test recall and sequencing of the process, balanced equations, and explanation of why industrial conditions are chosen as a compromise.

  • describe sulfuric acid as a major industrial chemical and state important uses such as manufacture of fertilisers, detergents, paints, dyes and chemicals where specified
  • describe the Contact process as the manufacture of sulfuric acid from sulfur or sulfide ores via sulfur dioxide and sulfur trioxide

About 6 h 45 min of study, lessons and core practice

• Crude oil, fuels and fractional distillation

  ≈ 2%1 h 15 min

  This topic covers crude oil as a finite fossil resource, hydrocarbons as compounds of carbon and hydrogen, and the separation of crude oil into useful fractions by fractional distillation. Exams test description and explanation of the distillation process, interpretation of boiling-point trends and uses of fractions, and simple ideas about fuels and petrochemicals.

  • describe crude oil as a finite resource formed from the remains of ancient biomass and explain why it is an important source of fuels and feedstock for the petrochemical industry
  • identify a hydrocarbon as a compound containing hydrogen and carbon only and recognise that crude oil is a mixture of hydrocarbons
  • explain how fractional distillation separates crude oil into fractions on the basis of different boiling points
  • interpret a fractional distillation column in terms of temperature gradient, evaporation, condensation and where fractions with different boiling points are collected
  • compare fractions by chain length, boiling point, viscosity and flammability using the general trend that shorter-chain hydrocarbons have lower boiling points and are more flammable
  • apply knowledge of named fractions and their typical uses, including refinery gases, petrol, kerosene, diesel, fuel oil and bitumen

• Alkanes, combustion and cracking

  ≈ 2%1 h 30 min

  This topic covers alkanes as saturated hydrocarbons, their complete and incomplete combustion, and cracking as a process that converts less useful hydrocarbons into shorter alkanes and alkenes. Exams test formula patterns, word and symbol equations, explanations of cracking, and evaluation of combustion products and their effects.

  • define alkanes as saturated hydrocarbons and use the homologous-series pattern for simple alkane formulae and structures
  • represent methane, ethane, propane and butane using molecular formulae, displayed formulae and simple structural formulae
  • write and interpret equations for the complete combustion of hydrocarbons to form carbon dioxide and water
  • explain incomplete combustion in limited oxygen and identify carbon monoxide and carbon, as well as water, as possible products
  • evaluate the risks and environmental effects associated with combustion products, including carbon monoxide as a toxic gas and carbon dioxide as a greenhouse gas
  • describe cracking as the thermal decomposition of long-chain hydrocarbons to produce shorter-chain alkanes and alkenes and explain why cracking is economically useful

• Alkenes, addition reactions and addition polymerisation

  ≈ 2.5%1 h 45 min

  This topic covers alkenes as unsaturated hydrocarbons, their reactions by addition, the bromine water test, and the formation of addition polymers. Exams test recognition and drawing of alkene structures, equations for addition reactions, and explanation of how monomers form polymers.

  • define alkenes as unsaturated hydrocarbons containing a carbon-carbon double bond and distinguish them from alkanes
  • represent ethene, propene and butene using molecular formulae, displayed formulae and simple structural formulae
  • describe and explain the reaction of alkenes with bromine water as a test for unsaturation, including the decolourisation of orange bromine water
  • write and interpret equations for addition reactions of alkenes with hydrogen, halogens and steam to form saturated products
  • describe addition polymerisation as the formation of very long molecular chains from many alkene monomers and explain that the double bond opens to form single bonds in the polymer chain
  • draw and interpret the repeating unit of an addition polymer from a given alkene monomer and identify the monomer from a simple polymer structure

• Alcohols, ethanol and fermentation

  ≈ 1.5%1 h 15 min

  This topic covers alcohols with ethanol as the main example, including structure, combustion, production by fermentation, and hydration of ethene. Exams test comparison of production methods, required conditions, balanced equations in simple cases, and uses of ethanol as a solvent, fuel and beverage alcohol.

  • identify ethanol as an alcohol and represent it using molecular, structural and displayed formulae
  • describe the complete combustion of ethanol and write the equation for its combustion to produce carbon dioxide and water
  • describe the production of ethanol by fermentation of aqueous sugar solutions using yeast under suitable conditions, including a warm temperature and the absence of oxygen
  • explain that fermentation produces a dilute ethanol solution and that ethanol can be obtained from the mixture by fractional distillation
  • describe the production of ethanol by hydration of ethene with steam and state the need for high temperature, a catalyst and pressure
  • compare fermentation and hydration of ethene as methods of manufacturing ethanol in terms of feedstocks, conditions, rate, purity and sustainability

• Carboxylic acids, esters and condensation polymers

  ≈ 2%1 h 45 min

  AQA onlyPearson Edexcel onlyOCR Chemistry A (Gateway) onlyOCR Chemistry B (Twenty First Century) onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA onlyEdexcel International GCSE Chemistry only

  This topic covers carboxylic acids and esters, esterification, and condensation polymerisation such as polyester formation. Exams test naming and recognising functional groups, describing characteristic properties and reactions, and interpreting how small molecules are eliminated during condensation polymerisation.

  • identify carboxylic acids by the -COOH functional group and represent simple examples such as ethanoic acid using molecular, structural and displayed formulae

About 7 h 30 min of study, lessons and core practice

• Qualitative analysis of gases, cations and anions

  ≈ 2%2 h

  This topic covers the standard GCSE/IGCSE qualitative tests used to identify common gases and selected cations and anions from observations, reagents and confirmatory results. Exams test recall of reagents and observations, interpretation of practical evidence, ionic equations in some specifications, and selection of suitable tests to distinguish unknown substances.

  • describe and apply the standard tests for hydrogen, oxygen, carbon dioxide and chlorine, including the reagent or method used and the positive observation
  • describe and apply tests for ammonia where required, including recognition from its characteristic smell, damp red litmus turning blue, or production during warming with alkali
  • identify metal cations from flame tests, including lithium, sodium, potassium, calcium and copper, using the characteristic flame colours
  • identify common metal cations using sodium hydroxide and, where required by the specification, aqueous ammonia, including observations for aluminium, calcium, magnesium, copper(II), iron(II) and iron(III) ions
  • identify carbonate, sulfate and halide ions using the standard test reagents and observations, including acid plus carbonate tests, acidified barium salt tests for sulfate, and acidified silver nitrate tests for chloride, bromide and iodide
  • interpret sequences of qualitative tests to deduce the identity of unknown salts, solutions or gases, and distinguish between similar ions using valid chemical evidence

• Purity, formulations, chromatography and Rf values

  ≈ 1.5%1 h 30 min

  This topic covers pure substances and formulations, plus paper chromatography as a method for separating and identifying soluble substances. Exams test definitions, practical procedure, interpretation of chromatograms, and calculation or use of $R_f$ values where included by the specification.

  • define a pure substance as a single element or single compound not mixed with any other substance, and distinguish purity from mixtures and formulations
  • define a formulation as a useful mixture designed as a product with components present in measured quantities to give required properties
  • explain how melting point and boiling point data can be used to assess purity, including that pure substances have sharp melting and boiling points while mixtures show a range
  • describe and apply the method of paper chromatography, including drawing a pencil baseline, placing spots correctly, choosing a suitable solvent, and allowing the solvent front to rise
  • interpret chromatograms to determine the number of substances present, identify whether samples are pure or mixtures, and compare unknowns with known reference substances

• Instrumental analysis and flame emission spectroscopy

  ≈ <1%1 h

  AQA onlyPearson Edexcel onlyOCR Chemistry A (Gateway) onlyOCR Chemistry B (Twenty First Century) onlyWJEC (Wales; updated spec with new Unit 3 from Sept 2026) onlyCCEA onlyEdexcel International GCSE Chemistry only

  This topic covers why instrumental methods are used and the core GCSE application of flame emission spectroscopy for detecting metal ions. Exams test advantages and limitations of instrumental analysis, recognition of spectral evidence, and interpretation of calibration data in specifications that include quantitative treatment.

  • explain why instrumental methods are often preferred to simple chemical tests, including their speed, sensitivity and ability to analyse small sample sizes

• Atmospheric composition, climate change and air pollution

  ≈ 2%1 h 30 min

  This topic covers the composition of Earth’s atmosphere, how it has changed over time, the greenhouse effect, climate change and major air pollutants. Exams test recall of atmospheric composition, explanation of environmental changes and pollutant effects, and evaluation of evidence and proposed solutions.

  • state the approximate composition of the present atmosphere and identify nitrogen and oxygen as the main components, with smaller amounts of argon, carbon dioxide and variable water vapour
  • describe the evidence-based stages in the evolution of Earth’s early atmosphere, including volcanic activity, formation of oceans, carbon dioxide decrease, and oxygen increase due to photosynthesis
  • explain the greenhouse effect in terms of infrared absorption and re-emission by greenhouse gases, and describe the role of carbon dioxide, methane and water vapour
  • evaluate evidence for climate change, including human activities that increase greenhouse gas concentrations such as combustion of fossil fuels, deforestation and agriculture
  • describe the sources and effects of major air pollutants, including carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates

• Water treatment, resource use and sustainable materials

  ≈ 1.5%1 h 30 min

  This topic covers potable water, wastewater treatment, finite and renewable resources, life-cycle thinking, and strategies for reducing environmental impact through reuse, recycling and sustainable material choices. Exams test process description, comparison of options, and evaluation of environmental, social and economic trade-offs.

  • describe how potable water can be produced from fresh water sources by filtration and sterilisation, and explain why desalination is used where fresh water is limited
  • describe the main stages of sewage and wastewater treatment, including screening, sedimentation, aerobic biological treatment and safe handling of sludge where specified
  • distinguish between finite and renewable resources and apply these ideas to fuels, metals, water and manufactured materials
  • evaluate the benefits and drawbacks of reusing and recycling materials, including reduced energy use and conservation of raw materials balanced against costs, collection and processing
  • apply life-cycle assessment ideas to compare products or materials, considering extraction, manufacture, use and disposal, while recognising that such assessments depend on the data and weighting used

• Practical skills, planning, measurement, evaluation and exam strategy

  ≈ 1.5%2 h

  This topic covers the cross-topic practical skills assessed in written papers and, for some specifications, separate practical components: planning methods, selecting apparatus, taking measurements, processing data, evaluating quality and working safely. Exams test these skills in unfamiliar contexts through method-writing, variables, graphing, calculations, error analysis and improvements.

  • plan an investigation by stating the aim, identifying independent, dependent and control variables, and selecting a valid method with appropriate apparatus
  • select and use suitable apparatus for measuring mass, volume, temperature, time and gas volume or gas production, considering precision, resolution and range
  • record observations and measurements appropriately, present data in suitable tables, and process results by calculating means, rates, concentrations or other derived quantities
  • interpret data using graphs and lines of best fit, identify patterns and anomalies, and draw conclusions that are consistent with the evidence
  • evaluate an experimental method by identifying sources of error, distinguishing random and systematic error, assessing accuracy, precision and repeatability, and suggesting realistic improvements

About 9 h 30 min of study, lessons and core practice