A Level Chemistry

• Enthalpy changes and calorimetry

  ≈ 1.9%1 h 30 min

  This topic covers enthalpy changes, standard enthalpy terms and experimental determination of enthalpy changes by calorimetry. Exams test definitions, sign conventions, energy profile ideas and calculations using $q=mc\Delta T$ and related assumptions about heat transfer.

  • Define and use the terms exothermic, endothermic, enthalpy change, standard enthalpy change, standard enthalpy change of reaction, formation, combustion and neutralisation.
  • Represent and interpret enthalpy changes on labelled energy level diagrams, including activation energy and the sign of $\Delta H$.
  • Calculate heat energy changes from experimental data using $q=mc\Delta T$ and relate this to molar enthalpy changes.
  • Determine enthalpy changes from calorimetry results for reactions in solution and for combustion experiments, including appropriate unit conversions.
  • Explain assumptions and sources of error in calorimetry, including heat loss, incomplete combustion and the use of water to model the surroundings.
  • Evaluate the reliability and accuracy of calorimetry data and suggest improvements to apparatus or method.

• Hess cycles, bond enthalpies and lattice energetics

  ≈ 2.8%2 h

  This topic develops indirect methods for finding enthalpy changes using Hess’s law, mean bond enthalpies and lattice energetics. Exams test construction and use of Hess cycles, Born–Haber cycles, and explanation of trends using ionic model ideas and covalency.

  • Apply Hess’s law to calculate unknown enthalpy changes from known enthalpy data, including formation and combustion cycles.
  • Construct and interpret Hess cycles using correct state symbols, directions and algebraic signs.
  • Use mean bond enthalpies to estimate enthalpy changes of reactions by comparing bonds broken and bonds formed.
  • Define lattice enthalpy and distinguish between lattice formation enthalpy and lattice dissociation enthalpy.
  • Construct and use Born–Haber cycles to calculate lattice enthalpy or related quantities such as electron affinity and enthalpy of formation.
  • Explain discrepancies between theoretical and experimental lattice enthalpy values in terms of ionic size, charge density and covalent character or polarisation.

• Entropy and Gibbs free energy

  ≈ 1.9%1 h 45 min

  This topic covers entropy change, feasibility and the use of Gibbs free energy to predict thermodynamic favourability. Exams test qualitative entropy reasoning and calculations involving $\Delta S$, $\Delta G=\Delta H-T\Delta S$ and the effect of temperature.

  • Define entropy as a measure related to the dispersal of energy or disorder in a system and describe entropy changes for changes of state and for reactions.
  • Predict the sign of system entropy change from changes in state, number of gaseous molecules and molecular complexity.
  • Calculate total entropy change from system and surroundings terms, using $\Delta S_{\text{total}}=\Delta S_{\text{system}}+\Delta S_{\text{surroundings}}$ and $\Delta S_{\text{surroundings}}=-\dfrac{\Delta H}{T}$ where appropriate.
  • Define Gibbs free energy change and use $\Delta G=\Delta H-T\Delta S$ with consistent units to calculate feasibility under stated conditions.
  • Interpret the sign of $\Delta G$ and explain how temperature can change whether a process is thermodynamically feasible.
  • Distinguish thermodynamic feasibility from reaction rate when discussing whether a reaction will occur.

• Reaction rates and collision theory

  ≈ 1.9%1 h 15 min

  This topic introduces rate of reaction, methods for measuring rate and collision theory explanations for factors affecting rate. Exams test experimental interpretation, graph-based rate determination and particle-level explanations using successful collisions and activation energy.

  • Define rate of reaction in terms of change in concentration of a reactant or product per unit time.
  • Measure or calculate rate from experimental data, including gas volumes, mass change, colour change, precipitate formation or concentration-time information.
  • Determine mean rate and estimate initial rate from graphical data using tangents or gradients.
  • Explain reaction rate in terms of collision frequency, energy of collisions and activation energy.
  • Explain the effects of concentration, pressure, surface area, temperature and catalysts on rate using collision theory.
  • Interpret and sketch Maxwell–Boltzmann distributions to show the effect of temperature and catalysts on the number of particles with energy greater than or equal to activation energy.

• Rate equations, orders, mechanisms and Arrhenius treatment

  ≈ 2.8%2 h 30 min

  This topic develops quantitative kinetics, including orders of reaction, rate equations, mechanisms, rate-determining steps and Arrhenius treatment. Exams test deduction of orders from data, half-life links, integrated graphical reasoning in some specifications, and calculations involving rate constants and activation energy.

  • Determine the order with respect to a reactant and the overall order from initial-rate data or other kinetic evidence, and write the corresponding rate equation.
  • Calculate the rate constant $k$ from rate data and concentrations, including correct units for different overall orders.
  • Interpret the effect of changing concentration on rate for zero-, first- and second-order behaviour and identify order from concentration-time, rate-concentration or half-life information.
  • Use half-life relationships for first-order reactions and, where required by the specification, apply integrated first-order treatment such as plotting appropriate linear graphs.
  • Relate a proposed reaction mechanism to the observed rate equation and identify the rate-determining step consistent with kinetic data.

• Dynamic equilibrium and Le Chatelier’s principle

  ≈ 1.9%1 h 15 min

  This topic covers reversible reactions, dynamic equilibrium and the prediction of equilibrium shifts using Le Chatelier’s principle. Exams test precise equilibrium language and application of changes in concentration, pressure and temperature to both yield and system response.

  • Define a reversible reaction and dynamic equilibrium in terms of equal forward and reverse reaction rates in a closed system.
  • Recognise when an equilibrium is established and distinguish equilibrium from completion of reaction.
  • Apply Le Chatelier’s principle to predict the effect of changing concentration, pressure or temperature on the position of equilibrium.
  • Explain equilibrium shifts for gaseous equilibria in terms of changes in total amount of gaseous substance and opposing imposed change.
  • Predict the effect of catalysts on the time taken to reach equilibrium and explain why catalysts do not change the equilibrium position.
  • Interpret experimental or industrial conditions in terms of equilibrium yield and compromise conditions.

• Equilibrium constants Kc and Kp

  ≈ 1.9%1 h 45 min

  This topic introduces quantitative equilibrium constants for homogeneous systems in terms of concentration and pressure. Exams test writing equilibrium expressions, calculating $K_c$ and $K_p$, deducing equilibrium composition and linking the magnitude of equilibrium constants to the extent of reaction.

  • Write expressions for $K_c$ and $K_p$ for homogeneous equilibria using stoichiometric coefficients correctly.
  • Calculate $K_c$ from equilibrium concentrations and calculate equilibrium concentrations from an initial mixture and a value of $K_c$.
  • Calculate $K_p$ from equilibrium partial pressures and determine partial pressures from mole fractions or total pressure where needed.
  • Interpret the magnitude of $K_c$ or $K_p$ to describe the position of equilibrium and the extent to which reactants are converted into products.
  • Explain how changes in temperature affect the value of an equilibrium constant and distinguish this from shifts caused by concentration or pressure changes.
  • Use appropriate units conventions for equilibrium constants where required by the specification and recognise cases where constants are treated as unitless.

• Acids, bases and pH calculations

  ≈ 1.9%1 h 45 min

  This topic covers Brønsted–Lowry acid–base theory, strong acids and bases, and pH calculations for fully dissociated species. Exams test definitions, ionic equations, neutralisation stoichiometry and calculations of pH, $[\text{H}^+]$ and $[\text{OH}^-]$.

  • Define acids and bases using the Brønsted–Lowry model and identify conjugate acid-base pairs.
  • Write ionic equations for acid-base reactions, including proton transfer and neutralisation.
  • Distinguish strong and weak acids and bases in terms of extent of dissociation, not concentration.
  • Calculate $\text{pH}$, $[\text{H}^+]$, $\text{pOH}$ and $[\text{OH}^-]$ for strong monoprotic acids and strong bases.
  • Calculate the concentrations of species after dilution or mixing for acid-base systems involving complete dissociation.
  • Use stoichiometric relationships to solve acid-alkali neutralisation and titration calculations for strong acids and strong bases.

• Weak acids, buffers and titration curves

  ≈ 1.9%2 h

  This topic extends acid–base chemistry to weak acids, acid dissociation constants, buffer solutions and titration curves. Exams test equilibrium-based pH calculations, buffer action, indicator choice and interpretation of strong/weak acid-base titration profiles.

  • Define acid dissociation constant $K_a$ and use it to compare the strengths of weak acids, including use of $\text{p}K_a$ where specified.
  • Calculate the pH of a weak acid solution from concentration and $K_a$, using appropriate approximations where justified by the specification.
  • Explain the action of a buffer solution in terms of equilibrium and the presence of a weak acid with its conjugate base, or a weak base with its conjugate acid where relevant.
  • Calculate the pH of buffer solutions from component concentrations and acid dissociation data using the required equilibrium relationships.
  • Interpret and sketch titration curves for strong acid-strong base, weak acid-strong base and other required combinations, identifying key regions such as initial pH, buffer region, equivalence point and end point.

• Solubility product and precipitation equilibria

  ≈ <1%1 h

  Cambridge International onlyPearson Edexcel International A Level only

  Equilibria involving sparingly soluble salts, including $K_{sp}$ expressions, solubility calculations and prediction of precipitation.

  • Write equilibrium expressions for the solubility product of sparingly soluble salts.
  • Calculate molar solubility from $K_{sp}$ and vice versa.
  • Use ionic concentrations to predict whether precipitation will occur.
  • Explain the effect of a common ion on solubility where required.
  • Apply precipitation equilibria to analytical and synthetic contexts.

About 16 h 45 min of study, lessons and core practice

• Oxidation states, redox equations and disproportionation

  ≈ 1.9%1 h 30 min

  This topic covers oxidation states, oxidation and reduction, balancing redox equations, and disproportionation in aqueous and inorganic systems. Exams test it through oxidation-number changes, ionic and half-equation construction, identification of oxidising and reducing agents, and explanation of disproportionation reactions.

  • assign oxidation states to atoms and ions in elements, compounds and complex ionic species using standard rules
  • identify oxidation and reduction from changes in oxidation state and electron transfer, and distinguish oxidising agents from reducing agents
  • balance redox equations in terms of atoms, charge and electrons using half-equations, including acidic conditions and ionic equations
  • construct and combine half-equations to produce overall redox equations for reactions of metals, halogens, halide ions and common inorganic oxidants or reductants
  • explain disproportionation as simultaneous oxidation and reduction of the same species and recognise examples involving halogens, halates or related inorganic species
  • interpret redox chemistry in experimental and written contexts, including feasibility clues from colour change, oxidation-state change and products formed

• Electrode potentials, electrochemical cells and feasibility

  ≈ 2.8%2 h 15 min

  This topic covers standard electrode potentials, electrochemical cell representation, and the prediction of reaction feasibility from electrochemical data. Exams test it through cell diagrams, calculation of $E^\circ_{\text{cell}}$, interpretation of redox trends, and evaluation of whether reactions are thermodynamically feasible under standard conditions.

  • define a standard electrode potential $E^\circ$ as the emf of a half-cell compared with the standard hydrogen electrode under standard conditions
  • describe the standard hydrogen electrode and the standard conditions used for electrode potentials, including solutions at about $1.0\ \text{mol dm}^{-3}$, gases at about $100\ \text{kPa}$ and a stated temperature, typically $298\ \text{K}$
  • interpret standard electrode potential data to compare oxidising and reducing strength of species and to rank species accordingly
  • construct conventional cell diagrams for electrochemical cells from given half-cells and identify the direction of electron flow
  • calculate standard cell potentials using $$E^\circ_{\text{cell}} = E^\circ_{\text{right}} - E^\circ_{\text{left}}$$ or equivalent reduction-potential conventions, and relate the sign and magnitude to feasibility

• Electrolysis and Faradaic calculations

  ≈ 1.9%1 h 30 min

  Cambridge International onlyPearson Edexcel International A Level only

  Electrolytic cells, electrode processes, product prediction and quantitative relationships between charge, amount of substance and mass or volume produced.

  • Predict the products formed at anode and cathode for molten and aqueous electrolytes.
  • Write half-equations and overall equations for electrolytic processes.
  • Calculate charge using $Q=It$ and relate charge to amount of substance using the Faraday constant.
  • Determine masses of metals or volumes of gases produced during electrolysis.
  • Apply electrolysis to contexts such as electroplating, purification or manufacture where specified.

About 5 h 15 min of study, lessons and core practice

• Periodic trends and Period 3 chemistry

  ≈ 1.9%1 h 45 min

  This topic covers periodicity across Period 3 and the chemistry of the Period 3 elements and their oxides/chlorides where specified at A Level. Exams test explanation of trends using nuclear charge, shielding and atomic structure, and application of these ideas to bonding, structure, acid-base behaviour and reactions with water.

  • Explain the trends across Period 3 in atomic radius, first ionisation energy, melting point, electrical conductivity and the transition from metallic to covalent character in terms of effective nuclear charge, shielding, atomic structure and bonding.
  • Interpret the physical properties of the Period 3 elements from $\text{Na}$ to $\text{Ar}$ by relating giant metallic, giant covalent and simple molecular structures to melting point and conductivity.
  • Describe and explain the reactions of Period 3 elements with oxygen to form oxides, and classify the oxides as basic, amphoteric, acidic or neutral where applicable.
  • Predict, write equations for and explain the reactions of Period 3 oxides with water, acids and bases, including the trend from strongly basic oxides through amphoteric aluminium oxide to acidic oxides.
  • Describe, compare and explain the reactions of Period 3 chlorides with water, including hydrolysis, acidity of the resulting solution and the contrasting behaviour of ionic and covalent chlorides.
  • Apply knowledge of Period 3 trends and compounds to unfamiliar examples, practical observations and exam data, including identifying likely structures, bonding types and acid-base behaviour.

• Group 2 chemistry

  ≈ 1.9%1 h 30 min

  This topic covers the chemistry of the Group 2 metals $\text{Be}$ to $\text{Ba}$, including trends in reactivity, compounds and some industrial and environmental applications. Exams test trend explanation, equation writing, qualitative observations and use of solubility and thermal stability ideas in practical and applied contexts.

  • Describe and explain the increasing reactivity of Group 2 metals down the group in terms of atomic radius, shielding and decreasing first and second ionisation energies.
  • Write equations for and explain the reactions of Group 2 metals with water and oxygen, and state the products formed with steam or air where relevant.
  • Describe the properties and uses of Group 2 oxides and hydroxides, including the trend in hydroxide solubility and alkalinity down the group.
  • Describe and explain the trend in thermal stability of Group 2 carbonates and nitrates, and write equations for their decomposition on heating.
  • Describe and explain the trend in solubility of Group 2 sulfates and the limited solubility trend of hydroxides, and apply these trends to compounds such as barium sulfate in medical imaging.

• Halogens and halide ions

  ≈ 1.9%1 h 30 min

  This topic covers the chemistry of the Group 17 halogens and halide ions, including redox trends, displacement reactions, disproportionation and analytical tests. Exams test prediction of reaction feasibility, writing ionic equations, explaining observations and linking oxidising power and reducing power to periodic trends.

  • Describe and explain the trends in colour, physical state, melting point, boiling point and oxidising ability of the halogens down Group 17.
  • Explain the decreasing reactivity of the halogens down the group in terms of atomic radius, shielding and attraction for an incoming electron, and relate this to electron affinity where appropriate.
  • Predict and write ionic equations for displacement reactions of halogens with aqueous halide ions, and identify the oxidising agent and reducing agent.
  • Describe and explain the reactions of halogens with water and alkalis, including disproportionation in cold dilute and hot concentrated alkali where specified.
  • Describe and explain the trends in reducing power of halide ions, including their reactions with concentrated sulfuric acid and the differing redox behaviour of $\text{Cl}^-$, $\text{Br}^-$ and $\text{I}^-$.

• Nitrogen, ammonia and nitrogen compounds

  ≈ 1.9%1 h 30 min

  Cambridge International only

  This topic covers the properties of nitrogen, the manufacture and reactions of ammonia, ammonium compounds and the chemistry of nitrogen oxides and nitrates where included by the specification. Exams test equilibrium and industrial conditions in the Haber process, acid-base and redox chemistry of nitrogen compounds, and interpretation of environmental and practical contexts.

  • Describe the bonding and relative lack of reactivity of nitrogen, and explain this in terms of the strength of the $\text{N} \equiv \text{N}$ bond.
  • State and explain the conditions and catalyst used in the Haber process, and evaluate the compromise between rate, yield, cost and sustainability in the manufacture of ammonia.
  • Write equations for and explain the reactions of ammonia as a base, as a ligand where treated elsewhere by the course, and as a reducing agent with metal oxides or oxygen where specified.
  • Describe the formation and reactions of ammonium ions and ammonium salts, including their behaviour with alkalis to release ammonia and their role in fertilisers.

• Sulfur, sulfuric acid and sulfates

  ≈ 1.9%1 h 30 min

  Cambridge International only

  This topic covers the allotropy and reactions of sulfur, the Contact process, sulfuric acid chemistry and the properties and uses of sulfates. Exams test industrial-process conditions, acid-base and redox reactions, thermal stability and solubility ideas, and application to analytical and environmental contexts.

  • Describe the structure, allotropy and key reactions of sulfur, including combustion in air and the formation of sulfur dioxide and sulfur trioxide.
  • State and explain the conditions and catalyst used in the Contact process, and evaluate the compromise between rate, yield, equilibrium position and economic or safety considerations.
  • Write equations for and explain the acid-base, oxidising and dehydrating reactions of sulfuric acid, distinguishing between dilute and concentrated sulfuric acid.
  • Describe and explain the reactions of sulfates and sulfites where specified, including thermal decomposition patterns, precipitation reactions and oxidation or reduction behaviour.

About 7 h 45 min of study, lessons and core practice

• Transition-metal properties, oxidation states and colours

  ≈ 1.9%1 h 30 min

  This topic covers the defining properties of transition elements, including variable oxidation states, coloured ions and key physical characteristics arising from $d$-subshell behaviour. Exams test explanation of these properties from electron configuration, prediction of oxidation states, and interpretation of colour changes in ions and compounds.

  • Define a transition element in terms of formation of at least one stable ion with an incomplete $d$ subshell, and distinguish transition metals from $d$-block elements that do not meet this definition.
  • Describe and explain the characteristic physical properties of transition metals, including relatively high melting points, high densities, strength, and catalytic behaviour, in terms of metallic structure and electron arrangement.
  • Deduce and write electron configurations for transition-metal atoms and ions, including loss of $4s$ electrons before $3d$ electrons in first-row transition-metal ions.
  • Determine and justify oxidation states of transition metals in ions, compounds and complex ions, and explain the occurrence of variable oxidation states.
  • Explain why many transition-metal ions and compounds are coloured in terms of splitting of $d$ orbitals and absorption of visible light causing $d$-$d$ electronic transitions.
  • Interpret observed colour changes for transition-metal ions in different oxidation states and use these observations in redox and identification contexts.

• Transition-metal complexes, ligands and stereochemistry

  ≈ 2.8%2 h 15 min

  This topic covers the structure and bonding of transition-metal complexes, the behaviour of ligands, and the shapes and stereoisomerism of coordination compounds. Exams test naming and formula writing, ligand substitution and complex formation equations, and analysis of geometrical and optical isomerism.

  • Define the terms ligand, coordinate bond, coordination number and complex ion, and classify ligands as monodentate, bidentate or multidentate using named examples such as $\ce{H2O}$, $\ce{NH3}$, $\ce{Cl^-}$, $\ce{CN^-}$, $\ce{en}$ and $\ce{EDTA^{4-}}$.
  • Draw, interpret and construct formulae for transition-metal complexes, including charges, oxidation states, coordination numbers and the number of ligands attached to the metal centre.
  • Predict and explain the shapes of common complexes, especially octahedral, tetrahedral and square planar, from coordination number and ligand arrangement.
  • Write equations for formation of complex ions and for ligand substitution reactions, including replacement of water ligands by $\ce{NH3}$, $\ce{Cl^-}$ or other ligands, and relate these changes to observed colour changes.

• Transition-metal redox, catalysis and related chemistry

  ≈ 2.8%2 h

  This topic covers the redox chemistry of transition metals, their role as homogeneous and heterogeneous catalysts, and related chemistry of selected ions and compounds. Exams test redox equations, interpretation of oxidation-state changes, explanation of catalytic action, and application of transition-metal chemistry in industrial and electrochemical contexts.

  • Write and balance redox equations involving transition-metal species using oxidation states, half-equations or electron transfer, including reactions of ions in different oxidation states.
  • Explain why transition metals readily undergo redox reactions in terms of the similar energies of their oxidation states and the relative ease of electron gain and loss.
  • Describe and explain the catalytic action of transition metals and their compounds, including heterogeneous catalysis at metal surfaces and homogeneous catalysis involving changes in oxidation state or formation of intermediates.
  • Apply knowledge of named transition-metal catalysts to familiar industrial and laboratory examples, such as iron in the Haber process, nickel in hydrogenation, and transition-metal ions in redox catalysis.

• Qualitative inorganic analysis of cations, anions and gases

  ≈ 1.9%1 h 45 min

  This topic covers the identification of inorganic ions and gases using standard qualitative tests, observations and confirmatory procedures. Exams test recall and application of reagent sequences, ionic equations, interpretation of precipitate and colour changes, and deduction of unknown ions from practical evidence.

  • Apply the standard test with aqueous sodium hydroxide and aqueous ammonia to identify common metal cations, including $\ce{Al^{3+}}$, $\ce{Ca^{2+}}$, $\ce{Cu^{2+}}$, $\ce{Fe^{2+}}$, $\ce{Fe^{3+}}$, $\ce{Cr^{3+}}$, $\ce{Zn^{2+}}$ and $\ce{NH4^+}$, from precipitate formation, colour and solubility in excess reagent.
  • Interpret ligand-exchange and complex-formation observations in qualitative analysis, especially where precipitates dissolve in excess aqueous ammonia or sodium hydroxide to give characteristic solutions.
  • Use acidified silver nitrate and acidified barium salt tests, with the correct prior acidification, to identify halide ions and sulfate ions and to distinguish between similar observations.
  • Describe and apply tests for carbonate, hydrogencarbonate, sulfite and related anions that evolve gases on addition of acid, including identification of the gas produced.

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

• Organic nomenclature, formulae and isomerism

  ≈ 1.9%1 h 45 min

  This topic covers the language and representations of organic chemistry: homologous series, functional groups, formulae and structural isomerism. Exams test accurate naming, drawing and classification of organic compounds, and interpretation of displayed, skeletal and molecular representations.

  • Identify homologous series and functional groups in alkanes, alkenes, halogenoalkanes, alcohols and related simple organic molecules.
  • Apply IUPAC conventions to name and draw organic compounds from displayed, structural, skeletal and molecular formulae.
  • Distinguish between empirical, molecular, general, displayed, structural and skeletal formulae and convert one representation into another.
  • Explain the meaning of homologous series in terms of common functional group, similar chemical properties and trends in physical properties.
  • Recognise and draw structural isomers, including chain isomerism, position isomerism and functional-group isomerism where applicable.
  • Calculate empirical and molecular formulae from percentage composition, masses or combustion data in an organic context.

• Alkanes and free-radical substitution

  ≈ 1.9%1 h 15 min

  This topic covers the structure, sources, properties and reactions of alkanes, including combustion and halogenation by free-radical substitution. Exams test explanation of low reactivity, mechanism recall, equation writing and evaluation of issues linked to fuels and atmospheric pollutants.

  • Describe the structural features of alkanes, including saturated hydrocarbons containing only single $\mathrm{C-C}$ and $\mathrm{C-H}$ bonds.
  • Explain the trend in boiling points of alkanes in terms of increasing molecular size and intermolecular London forces.
  • Write equations for complete and incomplete combustion of alkanes and relate these reactions to the use of alkanes as fuels.
  • Evaluate the environmental and health effects of combustion products, including carbon dioxide, carbon monoxide, unburnt hydrocarbons, particulates, sulfur dioxide and oxides of nitrogen, where these are included by the specification.
  • Describe the reaction of alkanes with chlorine or bromine in ultraviolet light as a free-radical substitution.
  • Apply the mechanism of free-radical substitution using the steps initiation, propagation and termination, with correct use of curly arrows and the dot symbol for radicals.

• Alkenes and electrophilic addition

  ≈ 1.9%1 h 30 min

  This topic covers the structure and reactivity of alkenes, including geometric isomerism and addition reactions across the carbon-carbon double bond. Exams test naming, equation writing, mechanism recall and prediction of products from reactions with bromine, hydrogen, hydrogen halides, steam and oxidising agents.

  • Describe alkenes as unsaturated hydrocarbons containing a $\mathrm{C=C}$ double bond and explain why this bond is the site of reaction.
  • Recognise and draw $E/Z$ or cis-trans isomerism where restricted rotation about the $\mathrm{C=C}$ bond and suitable substituents allow it.
  • Write equations for the reactions of alkenes with hydrogen, halogens, hydrogen halides and steam.
  • Explain the decolourisation of bromine water as a test for unsaturation.
  • Apply the mechanism of electrophilic addition to reactions of alkenes with bromine and hydrogen bromide, using correct curly-arrow notation and identifying the electrophile.
  • Predict major products of alkene addition reactions, including asymmetric addition to unsymmetrical alkenes where carbocation stability is relevant at this level.

• Organic mechanisms and reactive intermediates

  ≈ 1.9%2 h

  This topic develops the common mechanistic language of organic chemistry and the reactive species used across the course. Exams test classification of bond fission, identification of electrophiles, nucleophiles and free radicals, and accurate curly-arrow representation in mechanism questions.

  • Distinguish between homolytic fission and heterolytic fission and relate each process to the formation of free radicals, electrophiles and nucleophiles where appropriate.
  • Define the terms free radical, electrophile and nucleophile using electron-pair language.
  • Represent the movement of electrons in organic mechanisms using full and half curly arrows correctly.
  • Identify bond polarity and partial charges in organic molecules and explain how these influence the site of attack in reactions.
  • Classify unfamiliar organic reaction steps as electrophilic addition, nucleophilic substitution, elimination or free-radical substitution from reagents and products.
  • Use the concept of intermediate species, including carbocations and free radicals, to explain observed reaction pathways and product formation at this level.

• Halogenoalkanes: substitution and elimination

  ≈ 2.8%2 h

  This topic covers the structure and reactions of halogenoalkanes, especially hydrolysis by nucleophilic substitution and elimination to form alkenes. Exams test practical interpretation, comparison of reactivity, mechanism selection and explanation of competing substitution and elimination pathways.

  • Identify primary, secondary and tertiary halogenoalkanes from structure and relate structure to typical reaction behaviour.
  • Explain the polar nature of the $\mathrm{C-X}$ bond and the role of hydroxide ion and other nucleophiles in nucleophilic substitution.
  • Write equations for the hydrolysis of halogenoalkanes and for substitution with hydroxide, cyanide, ammonia and other specified nucleophiles where included by the specification.
  • Apply the mechanisms of nucleophilic substitution, including $\mathrm{S_N1}$ and $\mathrm{S_N2}$ where required by the specification, using correct curly-arrow notation.
  • Describe and explain elimination of hydrogen halides from halogenoalkanes using alcoholic hydroxide to form alkenes.
  • Interpret practical evidence from halogenoalkane hydrolysis, including precipitation with silver nitrate after warming, and compare the relative rates of hydrolysis of chloro-, bromo- and iodoalkanes in terms of bond enthalpy.

• Alcohols and phenols

  ≈ 1.9%1 h 45 min

  This topic covers the structure, preparation, reactions and oxidation of alcohols, together with the distinctive acidity and reactions of phenols. Exams test classification, practical oxidation conditions, substitution and dehydration reactions, and comparison of alcohols with phenols using equations and explanations.

  • Classify alcohols as primary, secondary or tertiary from their structures and relate classification to oxidation behaviour.
  • Describe methods of preparing alcohols, including hydration of alkenes and hydrolysis of halogenoalkanes, where these routes are specified.
  • Write equations for the combustion, oxidation, substitution and dehydration reactions of alcohols under stated conditions.
  • Explain oxidation of primary alcohols to aldehydes and carboxylic acids and of secondary alcohols to ketones, including the choice of oxidising agent, distillation or reflux, and observation of colour change where applicable.
  • Describe elimination of water from alcohols to form alkenes and substitution by hydrogen halides or phosphorus halides to form halogenoalkanes where required by the specification.

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

• Arenes and electrophilic substitution

  ≈ 1.9%1 h 30 min

  This topic covers the structure, bonding and characteristic reactions of arenes, especially benzene, and the mechanisms and conditions for electrophilic substitution. Exams test explanation of benzene’s stability, interpretation of directing effects, and application of nitration, halogenation, Friedel–Crafts and side-chain oxidation in synthesis routes.

  • Explain the bonding in benzene using a delocalised $\pi$ electron model, describe its planar hexagonal structure and account for its unusual stability and tendency to undergo substitution rather than addition.
  • Compare the reactions of benzene with alkenes and apply this comparison to predict products and conditions for electrophilic substitution.
  • Describe and write equations for the nitration and halogenation of benzene, including reagents, catalysts, conditions and the generation of the electrophile.
  • Explain and apply the mechanism of electrophilic substitution in benzene, including attack by the electrophile, formation of the intermediate and loss of $\text{H}^+$ to restore aromaticity.
  • Describe Friedel–Crafts acylation and alkylation of benzene, including the role of halogenoalkanes or acyl chlorides and $\text{AlCl}_3$/$\text{FeCl}_3$-type catalysts, and predict the products formed.
  • Interpret the directing and activating effects of substituents already attached to the benzene ring, including phenol, phenylamine, halogens and alkyl groups, and apply oxidation of alkylbenzene side chains to carboxylic acids in synthetic contexts.

• Carbonyl compounds and nucleophilic addition

  ≈ 1.9%1 h 45 min

  This topic covers aldehydes and ketones: their structure, naming, physical properties, oxidation, reduction and nucleophilic addition reactions. Exams typically test reaction prediction, reagent choice, mechanism writing and distinction between aldehydes and ketones using oxidation tests and spectra.

  • Identify and name aldehydes and ketones, describe the polar $\text{C}=\text{O}$ bond and explain how the carbonyl group affects physical properties and reactivity.
  • Apply oxidation reactions of aldehydes and ketones, including oxidation of aldehydes to carboxylic acids with acidified dichromate(VI), Tollens’ reagent or Fehling’s/Benedict-type reagents where required by the board, and explain why ketones are resistant under these conditions.
  • Apply reduction of aldehydes and ketones to primary and secondary alcohols using suitable reducing agents such as $\text{NaBH}_4$, and write balanced equations for these transformations.
  • Explain and apply nucleophilic addition to aldehydes and ketones, including reaction with hydrogen cyanide to form hydroxynitriles and reaction with $2,4$-dinitrophenylhydrazine to form derivatives where specified.

• Carboxylic acids, esters and acyl derivatives

  ≈ 1.9%2 h

  This topic covers the structures, reactions and preparations of carboxylic acids, esters and reactive acyl derivatives such as acyl chlorides and acid anhydrides. Exams test equations, mechanisms, reagent choice, hydrolysis and acylation reactions, often within practical or multistep synthesis contexts.

  • Identify, name and describe the structures and physical properties of carboxylic acids, esters and acyl derivatives, relating acidity and boiling temperature to bonding and intermolecular forces.
  • Describe and apply the preparation and reactions of carboxylic acids, including oxidation of primary alcohols and aldehydes, reaction with metals, bases, carbonates and alcohols, and reduction where required by the specification.
  • Explain and apply esterification and hydrolysis of esters under acidic and alkaline conditions, including the use of reflux, catalysts and the formation of carboxylic acids, alcohols or carboxylate salts.
  • Describe the structure and high reactivity of acyl chlorides and acid anhydrides, and write equations for their reactions with water, alcohols, phenols, ammonia and amines.
  • Explain and apply nucleophilic addition-elimination mechanisms for acylation reactions of acyl derivatives, using correct intermediates and elimination steps.

• Organic nitrogen compounds: amines, amides and aromatic amines

  ≈ 2.8%2 h

  This topic covers aliphatic and aromatic amines, amides and related nitrogen chemistry, including basicity, preparation, acylation and diazonium chemistry where specified. Exams test comparison of basicity, mechanism and equation writing, and use of nitrogen compounds in synthesis and identification.

  • Identify and name primary, secondary and tertiary amines and amides, and explain the physical properties and bonding of these organic nitrogen compounds.
  • Explain the basicity of amines, compare the basic behaviour of aliphatic amines, ammonia and aromatic amines, and justify trends using availability of the lone pair and delocalisation.
  • Describe the preparation of aliphatic amines from halogenoalkanes, nitriles or reduction routes, and of aromatic amines from nitroarenes where specified, including suitable reagents and conditions.
  • Write equations for reactions of amines with acids, halogenoalkanes and acylating agents, and explain the formation of ammonium salts and substituted amides.
  • Describe and apply the chemistry of amides, including their formation from acyl chlorides, acid anhydrides, carboxylic acids or esters with ammonia or amines, and their hydrolysis under acidic or alkaline conditions where specified.

• Amino acids and proteins

  ≈ 1.9%1 h 30 min

  This topic covers the structure and behaviour of amino acids and proteins, including zwitterions, acid-base properties, peptide bond formation and hydrolysis. Exams test structure drawing, pH-dependent behaviour, condensation reactions and interpretation of protein-related hydrolysis or biochemical data.

  • Describe the general structure of $\alpha$-amino acids, recognise optical isomerism where present and classify amino acids as compounds containing both amine and carboxylic acid functional groups.
  • Explain the amphoteric behaviour of amino acids and represent their ionic forms, including cationic, zwitterionic and anionic species at different pH values.
  • Interpret the effect of pH on amino acid behaviour, including reactions with acids and bases and, where specified, migration or lack of migration in electric fields relative to the isoelectric point.
  • Explain condensation reactions between amino acids to form peptides and proteins, identify the peptide link, and write equations for dipeptide and polypeptide formation.
  • Describe hydrolysis of peptides and proteins to amino acids and apply this to analysis or synthesis questions.

• Addition and condensation polymers

  ≈ <1%1 h

  This topic covers the formation, structure, properties and disposal considerations of addition and condensation polymers. Exams test repeat-unit drawing, monomer identification, polymerisation equations and comparison of polymer types in terms of linkages, hydrolysis and environmental impact.

  • Explain addition polymerisation of alkenes and substituted alkenes, draw repeat units and identify monomers from polymer structures.
  • Explain condensation polymerisation, including formation of polyesters and polyamides from monomers with two functional groups, and draw the repeating structures produced.
  • Compare addition and condensation polymers in terms of monomer type, by-products formed, bonding and susceptibility to hydrolysis.
  • Describe hydrolysis of condensation polymers such as polyesters and polyamides under acidic or alkaline conditions and predict the organic products formed.
  • Evaluate issues related to polymer use and disposal, including persistence, recyclability, feedstocks and biodegradable alternatives, using chemistry to justify points where required.

• Organic synthesis, multistep routes and retrosynthesis

  ≈ 2.8%2 h 30 min

  This topic integrates the organic chemistry course into planning, evaluating and executing multistep syntheses using functional-group interconversions, mechanisms and analytical evidence. Exams test route design, retrosynthetic disconnections, reagent selection, feasibility, yield and purification across unfamiliar but specification-faithful contexts.

  • Apply functional-group interconversions across the A Level organic specification to convert starting materials into target molecules using feasible reagents, conditions and intermediates.
  • Plan multistep synthetic routes, including order of reactions, chemoselectivity and the use of oxidation, reduction, substitution, elimination, addition, acylation and hydrolysis steps.
  • Use retrosynthetic analysis to identify strategic bond disconnections, suitable precursors and alternative pathways to target compounds.
  • Evaluate competing routes in terms of number of steps, atom economy, yield, availability of reagents, purification and likely side-products.
  • Integrate mechanisms, reaction conditions and analytical data to justify synthetic choices, identify intermediates and confirm structures of products.

• Nitriles and cyanide chemistry

  ≈ 1.9%1 h 30 min

  Preparation and reactions of nitriles, including carbon-chain extension, hydrolysis and reduction, plus cyanide addition to carbonyl compounds where specified by the board.

  • Describe the formation of nitriles from halogenoalkanes using $CN^-$ as a nucleophile.
  • Explain how nitriles are hydrolysed to carboxylic acids or related products under acidic or alkaline conditions.
  • Predict and apply the reduction of nitriles to primary amines in synthesis routes.
  • Use nitriles to extend carbon chains in multistep organic synthesis.
  • Interpret the formation of hydroxynitriles from aldehydes and ketones where required by the specification.

About 13 h 45 min of study, lessons and core practice

• Chromatography and separation techniques

  ≈ 1.9%1 h 30 min

  This topic covers the principles, methods and interpretation of chromatographic and related separation techniques used across A Level chemistry, especially paper/TLC and, where specified by boards, column-based instrumental methods such as gas chromatography. Exams test both practical understanding and the ability to interpret chromatograms, retention data and evidence for identity/purity.

  • Explain the principles of separation by chromatography in terms of differential distribution between a mobile phase and a stationary phase.
  • Carry out and interpret paper chromatography and thin-layer chromatography, including the choice of baseline, solvent level, locating spots and using a chromatogram to compare substances.
  • Calculate and use $R_f$ values from chromatograms, and evaluate the limitations of $R_f$ data for identification under different experimental conditions.
  • Interpret chromatographic evidence to assess the number of components in a mixture and the purity or identity of a substance by comparison with standards.
  • Explain the use of gas chromatography and related retention data for separating volatile compounds, including interpretation of peak position and peak area where required.
  • Select appropriate separation or purification techniques for mixtures and reaction products, including filtration, crystallisation, solvent extraction, distillation and chromatography, with justification based on physical properties.

• Infrared spectrometry, mass spectrometry and structure deduction

  ≈ 2.8%2 h

  This topic covers how infrared spectroscopy and mass spectrometry are used to identify compounds and deduce structures from analytical data. Exams typically combine spectra with formulae, elemental composition and reaction information in multistep structure-deduction questions.

  • Interpret infrared spectra using absorption data to identify characteristic bond vibrations and functional groups, including $\text{O–H}$, $\text{N–H}$, $\text{C=O}$, $\text{C–O}$ and unsaturated bonds where specified.
  • Explain how infrared spectroscopy can be used to confirm the presence or absence of functional groups and distinguish between possible structures.
  • Interpret mass spectra in terms of the molecular ion, fragment ions and relative abundance, and use $m/z$ data to deduce molecular mass and likely fragments.
  • Use high-resolution or accurate-mass data, where specified, to determine molecular formula from exact masses or from a molecular ion together with isotopic information.
  • Interpret isotopic patterns in mass spectra, including characteristic halogen patterns, to infer the presence of elements such as chlorine and bromine.

• NMR spectroscopy for structure determination

  ≈ 2.8%2 h 15 min

  This topic covers the interpretation of $^1\text{H}$ and, where included by specification, $^{13}\text{C}$ NMR spectra for structure determination. Exams test reading spectra, relating chemical shifts to environments and integrating NMR with other analytical evidence to identify unknown organic compounds.

  • Explain the origin of NMR signals in terms of nonequivalent nuclei in different chemical environments and the use of a reference standard.
  • Interpret $^1\text{H}$ NMR spectra using chemical shift, peak area and splitting patterns to determine the number, type and neighbouring relationships of proton environments.
  • Apply the $n+1$ rule to simple spectra and recognise when proton environments do not split or are not split in straightforward ways under A Level conditions.
  • Interpret $^{13}\text{C}$ NMR spectra, where required, to determine the number of distinct carbon environments and identify likely carbon types from chemical shift data.
  • Use NMR data together with molecular formula, infrared spectra, mass spectra and known reactions to deduce complete structures of organic compounds.

• Volumetric analysis, calorimetry and standard laboratory methods

  ≈ 1.9%2 h

  This topic covers core quantitative practical methods, especially titration, solution preparation and calorimetry, together with the standard laboratory procedures that underpin written practical questions. Exams test method knowledge, calculations from practical data and evaluation of accuracy, precision and technique.

  • Prepare a standard solution from a solid or by dilution using appropriate apparatus and technique, including accurate weighing, transfer, rinsing and making up to the mark.
  • Carry out and calculate results from acid-base and redox titrations, including concordant titres, mean titre selection, stoichiometric relationships and concentration determination.
  • Select suitable indicators or detection methods for titrations and justify the choice from the chemistry of the system and the steepness of the titration curve where relevant.
  • Explain the principles of calorimetry for measuring enthalpy changes using temperature change, mass or volume, and specific heat capacity assumptions.
  • Calculate enthalpy changes from calorimetry data and evaluate significant sources of error such as heat loss, incomplete combustion, evaporation and instrument limitations.

• Preparing, purifying and characterising products

  ≈ <1%1 h 15 min

  This topic covers the practical steps used to make, isolate, purify and check the identity or purity of inorganic and organic products. Exams test choice of method, sequencing of operations and interpretation of evidence such as melting point, boiling point, yield and chromatographic or spectral data.

  • Plan or describe laboratory preparations of products using appropriate reagents, conditions and apparatus, including reflux, distillation, controlled addition and heating where relevant.
  • Select and justify methods for isolating products from reaction mixtures, including filtration, separating funnel use, solvent extraction, washing, drying and evaporation.
  • Explain and apply purification methods such as recrystallisation, simple distillation, fractional distillation and chromatography according to the properties of the substance and impurities present.
  • Calculate percentage yield and percentage atom economy where relevant to practical synthesis, and interpret low yield in terms of side reactions, incomplete reaction or product loss during transfer and purification.
  • Use melting point, boiling point and chromatographic or spectroscopic evidence to assess product identity and purity.

• Processing data, uncertainty and graphical analysis

  ≈ 1.9%1 h 15 min

  This topic covers the mathematical and evaluative treatment of experimental data, including uncertainties, errors, graph work and justified conclusions. Exams test numerical processing, presentation of data and the ability to judge reliability and validity from experimental evidence.

  • Process raw experimental data correctly, including unit conversion, use of significant figures, mean values and exclusion of anomalous results only with justification.
  • Distinguish between accuracy, precision, repeatability, reproducibility, random error and systematic error, and apply these ideas to practical data and methods.
  • Estimate, combine and express measurement uncertainties appropriately for practical work, including percentage uncertainty and the effect of uncertainty in derived quantities.
  • Plot and interpret suitable graphs, including selection of axes, scales and best-fit lines or curves, and use graphical methods to determine relationships, gradients, intercepts or end-points.
  • Evaluate the quality of data from scatter, concordance, outliers and uncertainty, and state whether conclusions are supported by the evidence.

• Planning investigations, evaluation and synoptic comprehension

  ≈ 1.9%1 h 45 min

  This topic covers the planning, adaptation and evaluation of chemical investigations and the synoptic use of knowledge from physical, inorganic, organic and analytical chemistry. Exams test unfamiliar practical contexts, extended data-rich questions and the ability to design valid methods and justify conclusions.

  • Plan an investigation to obtain reliable data, identifying the independent, dependent and control variables, the apparatus, the measurements required and the method for processing results.
  • Select suitable reagents, techniques and analytical methods to answer a chemical question, with justification based on the chemistry involved and the precision or validity required.
  • Assess hazards and risks and propose appropriate control measures, including safe handling, heating, disposal and use of personal protective equipment.
  • Evaluate experimental procedures and conclusions by identifying strengths, limitations, sources of error and specific improvements linked to the method or apparatus.
  • Apply synoptic chemical knowledge to unfamiliar contexts, integrating ideas from equilibria, energetics, kinetics, organic reactions, inorganic tests and analytical evidence.

• Qualitative organic analysis

  ≈ 1.9%1 h 15 min

  Test-tube reactions and observations used to identify and distinguish organic functional groups, linked to confirmatory analysis and structure deduction.

  • Select suitable reagents to test for alkenes, halogenoalkanes, alcohols, phenols, aldehydes, ketones and carboxylic acids.
  • Interpret positive and negative observations from common qualitative organic tests.
  • Distinguish between related functional groups using confirmatory sequences of tests.
  • Link reaction observations to likely structures and reaction classes.
  • Evaluate the limits and reliability of qualitative tests alongside spectroscopic evidence.

About 13 h 15 min of study, lessons and core practice