A-level Chemistry Exam Study Guide (2027)
Everything the A-level Chemistry Exam tests, topic by topic: what each section covers, the facts that come up most, and how to study it. Pair it with the free 15-question practice test.
The exam at a glance
| Questions | AQA: 3 written papers of 105, 105 and 90 marks (300 marks in total) |
|---|---|
| Time | 6 hours in total (3 × 2 hours) |
| Grades and pass mark | Grades run from A* to E, and grade E is a pass. Boundaries are set after every exam series, so aim for 70% in practice |
| Format | Written exam, calculator allowed, data booklet provided. No tiers. The practical endorsement is assessed by your teacher and reported separately as Pass or Not classified |
| Exam boards | AQA, OCR and Pearson Edexcel |
| Test provider | At your school or college, or as a private candidate at an exam centre that accepts them (and can arrange the practical endorsement) |
Mind map: the whole exam on one screen
Read the complete A-level Chemistry study notes for “Atomic Structure, Amount of Substance and Bonding”
Our first full set of comprehensive notes, about 20 minutes of reading: Sub-shells and electron configurations · Ionisation energies · Time of flight mass spectrometry · Amount of substance · Ionic, covalent and metallic bonding · Shapes of molecules and ions · Electronegativity and intermolecular forces, a worked exam example, the traps examiners use and a one-minute recap. Create a free account to read it and see how premium notes work before you decide.
1. Atomic Structure, Amount of Substance and Bonding
AQA 3.1.1 to 3.1.3: sub-shells and ionisation energies, time of flight mass spectrometry, the mole and the ideal gas equation, titrations and yields, ionic, covalent and metallic bonding, shapes of molecules, electronegativity and intermolecular forces. Assumed everywhere else in the course.
Key facts
- Electron configurations fill 1s 2s 2p 3s 3p 4s 3d; chromium is [Ar] 3d⁵ 4s¹ and copper [Ar] 3d¹⁰ 4s¹. Transition metal atoms lose 4s electrons before 3d when forming ions.
- First ionisation energy: the energy needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions. It generally increases across a period, with dips at Group 3 (new p sub-shell) and Group 6 (spin-pair repulsion).
- Time of flight mass spectrometry: ionisation (electron impact or electrospray), acceleration to constant kinetic energy, ion drift, detection. Lighter ions arrive first; Ar is calculated from m/z values and abundances.
- n = mass ÷ Mr; n = concentration × volume (dm³); pV = nRT with p in Pa, V in m³, T in K and R = 8.31 J K⁻¹ mol⁻¹.
- Percentage yield = (actual ÷ theoretical) × 100; atom economy = (Mr of desired product ÷ total Mr of reactants) × 100. Empirical formula from percentage composition, molecular formula from Mr.
- VSEPR: electron pairs repel to be as far apart as possible; lone pair-lone pair > lone pair-bond pair > bond pair-bond pair. Each lone pair reduces the angle by about 2.5°. Shapes: linear 180°, trigonal planar 120°, tetrahedral 109.5°, trigonal bipyramidal 90° and 120°, octahedral 90°.
- Electronegativity is the power of an atom to attract the pair of electrons in a covalent bond. Polar bonds in a symmetrical molecule (CO₂, CCl₄) cancel, so the molecule is non-polar.
- Intermolecular forces: induced dipole-dipole (van der Waals) forces increase with the number of electrons; permanent dipole-dipole; hydrogen bonding between a δ+ H on N, O or F and a lone pair on N, O or F. Hydrogen bonding explains the high boiling point of water and why ice is less dense than liquid water.
Flashcards
Exam tip: In the ideal gas equation, unit conversion is where most marks are lost: cm³ × 10⁻⁶ and dm³ × 10⁻³ give m³, kPa × 1000 gives Pa, and °C + 273 gives K.
2. Energetics, Kinetics and Equilibria
AQA 3.1.4 to 3.1.7 (Year 1 physical chemistry): enthalpy changes, calorimetry, Hess's law, bond enthalpies, collision theory and the Maxwell-Boltzmann distribution, catalysts, equilibrium position, Kc and redox.
Key facts
- Standard conditions: 100 kPa and a stated temperature, usually 298 K. ΔfH is the enthalpy change when 1 mol of a compound forms from its elements in their standard states; ΔcH when 1 mol of a substance is completely burned in oxygen.
- Calorimetry: q = mcΔT (q in J, m is the mass of water or solution in g, c = 4.18 J g⁻¹ K⁻¹); ΔH = −q ÷ n, converted to kJ mol⁻¹.
- Hess's law: the enthalpy change for a reaction is independent of the route. From combustion data, ΔH = Σ ΔcH(reactants) − Σ ΔcH(products); from formation data, ΔH = Σ ΔfH(products) − Σ ΔfH(reactants).
- Mean bond enthalpies give less accurate values than Hess cycles because they are averages over many compounds.
- Maxwell-Boltzmann distribution: area under the curve is the total number of molecules; raising the temperature moves the peak right and lower, so more molecules have energy ≥ Ea. A catalyst lowers Ea.
- Le Chatelier's principle: if a factor affecting an equilibrium changes, the position shifts to oppose the change. Catalysts do not change the position, only the time to reach equilibrium.
- Kc = [products]^coefficients ÷ [reactants]^coefficients for a homogeneous equilibrium. Only temperature changes the value of Kc.
- Redox: oxidation is loss of electrons, reduction is gain. Oxidation states: elements 0, O usually −2 (−1 in peroxides), H usually +1 (−1 in metal hydrides). Combine half-equations by balancing electrons.
Flashcards
Exam tip: Write the Hess cycle or the formula line before you substitute numbers. Sign errors are the main cause of lost marks, and the method mark is still available if the arithmetic slips.
3. Further Physical Chemistry
AQA 3.1.8 to 3.1.12 (Year 2 physical chemistry): Born-Haber cycles, enthalpies of solution, entropy and Gibbs free energy, rate equations and the Arrhenius equation, Kp, electrode potentials and cells, and acids, bases, pH and buffers.
Key facts
- Born-Haber cycles calculate lattice enthalpy from atomisation, ionisation energies, electron affinities and ΔfH. Differences between theoretical (perfect ionic model) and experimental values show covalent character.
- Enthalpy of solution = lattice dissociation enthalpy + sum of enthalpies of hydration of the ions.
- ΔG = ΔH − TΔS, with ΔS in kJ K⁻¹ mol⁻¹ when ΔH is in kJ mol⁻¹. A reaction is feasible when ΔG ≤ 0; the temperature at which it becomes feasible is T = ΔH ÷ ΔS.
- Rate = k[A]^m[B]^n. Orders come from experiment, not the equation. Zero order: rate does not change with concentration; first order: rate doubles when concentration doubles; second order: rate quadruples. The rate-determining step contains the species in the rate equation.
- Arrhenius equation: k = Ae^(−Ea/RT); ln k = −Ea/RT + ln A, so a plot of ln k against 1/T has gradient −Ea/R.
- Kp uses partial pressures: partial pressure = mole fraction × total pressure. Like Kc, only temperature changes Kp.
- Standard electrode potentials are measured against the standard hydrogen electrode (1.00 mol dm⁻³ H⁺, 100 kPa H₂, 298 K, Pt electrode). EMF = E(right, more positive) − E(left). The more positive electrode is reduced.
- pH = −log[H⁺]; Kw = [H⁺][OH⁻] = 1.00 × 10⁻¹⁴ mol² dm⁻⁶ at 298 K; Ka = [H⁺][A⁻] ÷ [HA] and pKa = −log Ka. At half-neutralisation pH = pKa. Buffers resist pH change when small amounts of acid or base are added.
Flashcards
Exam tip: Rate-equation questions from tables: change one concentration at a time and compare the rates. Write the factor change in concentration and in rate side by side before deciding the order.
Test yourself on these topics
Take the free 15-question A-level Chemistry test, then save your results to unlock your Readiness Score and the mistakes bank.
4. Periodicity, Group 2 and the Halogens
AQA 3.2.1 to 3.2.3 and 3.2.4 (inorganic chemistry, Paper 1): trends across Period 3, the alkaline earth metals and their compounds, the halogens and halide ions, and the reactions of Period 3 elements and oxides.
Key facts
- Across Period 3 atomic radius decreases and first ionisation energy generally increases because nuclear charge increases with similar shielding. Melting points peak at silicon (macromolecular).
- Down Group 2 atomic radius increases, first ionisation energy decreases and reactivity increases. Mg reacts with steam to form MgO and H₂; the others react with cold water to form hydroxides.
Flashcards
Exam tip: Learn the halide and sulfuric acid reactions as a table of products and oxidation-state changes for sulfur (+6 to +4, 0 and −2). Questions often ask for an equation and the role of each reagent.
5. Transition Metals and Inorganic Reactions
AQA 3.2.5 and 3.2.6: properties of transition metals, complex ions and their shapes, ligand substitution and the chelate effect, colour, variable oxidation states, redox titrations, catalysis, and reactions of metal-aqua ions.
Key facts
- Transition metals (Ti to Cu) have an incomplete d sub-shell in an atom or ion. Characteristic properties: complex formation, coloured ions, variable oxidation states and catalytic activity.
- A complex is a central metal atom or ion with coordinately bonded ligands. Coordination number 6 is usually octahedral, 4 is tetrahedral (for example [CuCl₄]²⁻) or square planar (cisplatin), and 2 is linear ([Ag(NH₃)₂]⁺, Tollens').
Flashcards
Exam tip: Make one table of metal-aqua ion reactions with columns for NaOH (some and excess), NH₃ (some and excess) and Na₂CO₃. Learn colours and formulae together, since equations are usually required.
6. Organic Chemistry: Alkanes to Alcohols
AQA 3.3.1 to 3.3.6 (Year 1 organic chemistry): nomenclature and isomerism, alkanes and cracking, free-radical substitution, halogenoalkanes, alkenes and electrophilic addition, alcohols, and organic analysis using tests, mass spectrometry and infrared.
Key facts
- IUPAC naming: longest chain, lowest locants, substituents in alphabetical order. Structural isomers differ in chain, position or functional group; E/Z isomers arise from restricted rotation about C=C with two different groups on each carbon (Cahn-Ingold-Prelog priority by atomic number).
- Fractional distillation separates crude oil; thermal cracking (high T and P) gives mainly alkenes, catalytic cracking (zeolite, slight pressure, about 450 °C) gives branched alkanes and aromatics for motor fuels.
Flashcards
Exam tip: For every reaction learn reagent, conditions, mechanism name and product as one unit. 'KOH' on its own scores nothing; 'aqueous, warm' or 'ethanolic, hot' is what decides the product.
7. Organic Chemistry: Aromatics, Carbonyls and Synthesis
AQA 3.3.7 to 3.3.16 (Year 2 organic chemistry): optical isomerism, aldehydes and ketones, carboxylic acids and derivatives, benzene and electrophilic substitution, amines, polymers, amino acids, proteins and DNA, organic synthesis, NMR and chromatography.
Key facts
- A chiral carbon has four different groups; the two enantiomers rotate plane-polarised light in opposite directions. A racemic mixture (50 : 50) is optically inactive. Nucleophilic addition to a planar C=O gives a racemic product.
- Aldehydes and ketones are reduced by NaBH₄ (nucleophilic addition of H⁻) to primary and secondary alcohols. KCN then dilute acid adds a CN group to form hydroxynitriles.
Flashcards
Exam tip: Build a reaction map of all functional groups with arrows labelled reagent and conditions. Synthesis and 'identify the unknown' questions both depend on it.
8. Practical Skills and Data Analysis
The 12 AQA required practicals, practical endorsement skills, uncertainty, significant figures, graphs and evaluating methods. At least 15% of A-level marks assess practical knowledge, much of it in Paper 3.
Key facts
- Required practicals include making a volumetric solution and acid-base titration, measuring an enthalpy change, rate by an initial-rates or continuous method, tests for ions, distillation and reflux, preparing and purifying an organic solid, an electrochemical cell, pH curves, and thin-layer chromatography.
- Percentage uncertainty = (uncertainty ÷ measured value) × 100. A burette or temperature change uses two readings, so the uncertainty doubles. Add percentage uncertainties when values are multiplied or divided.
Flashcards
Exam tip: When asked to evaluate a method, name a specific error, state its effect on the result (too high or too low), and give a specific improvement. Vague answers such as 'human error' score nothing.
How to pass
- Papers 1 and 2 give you 105 marks in 120 minutes, a little over 1 minute per mark. Spend about 30 seconds on each 1-mark multiple-choice question in Paper 3 to leave time for the practical questions.
- In calculations, keep full calculator values until the end and give the answer to the number of significant figures the data justifies, with units. Mark schemes often penalise wrong significant figures and missing units.
- Draw mechanisms with curly arrows starting from a lone pair or a bond and ending at an atom or bond. Missing lone pairs and partial charges are the most common lost marks.
- Learn the exact wording of definitions such as first ionisation energy, electronegativity, standard enthalpy of formation and Brønsted-Lowry acid. They are quick marks that are often only half remembered.
- Paper 3 can test any content plus the 12 required practicals. Learn each practical's method, the apparatus, sources of error and how to calculate percentage uncertainty.
Frequently asked questions
How long should I study for the A-level Chemistry exam?
Most students do best starting 10 to 12 weeks before the first paper, with 30 to 45 minutes a day per subject. You're ready once your Readiness Score has stayed at 80 or higher for about a week.
Can I take the A-level Chemistry exam online?
No. A-level Chemistry is a written exam sat in person at your school, college or an approved exam centre. Format: written exam, calculator allowed, data booklet provided. No tiers. The practical endorsement is assessed by your teacher and reported separately as Pass or Not classified. Check your exam board's timetable for dates.
What score do I need to pass the A-level Chemistry exam?
Grades run from A* to E, and grade E is a pass. Boundaries are set after every exam series, so aim for 70% in practice. The exam has aqa: 3 written papers of 105, 105 and 90 marks (300 marks in total) and a time limit of 6 hours in total (3 × 2 hours).
What are the most tested topics?
The outline covers atomic structure, amount of substance and bonding, energetics, kinetics and equilibria, further physical chemistry, periodicity, group 2 and the halogens, transition metals and inorganic reactions, organic chemistry: alkanes to alcohols, organic chemistry: aromatics, carbonyls and synthesis, practical skills and data analysis. Use the free practice test to see which ones you need most.
The premium A-level Chemistry study path
Premium A-level Chemistry prep is studied one topic at a time. Each step starts with that topic's key notes and flashcard deck, then its own question sets of 25, so you master one topic before you move to the next. When every topic is strong, the 6 full mock exams show you're ready.
Your step-by-step study path
- 1Atomic Structure, Amount of Substance and Bonding8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Notes free with an account
- 2Energetics, Kinetics and Equilibria8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 3Further Physical Chemistry8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 4Periodicity, Group 2 and the Halogens8 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 5Transition Metals and Inorganic Reactions7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 6Organic Chemistry: Alkanes to Alcohols7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 7Organic Chemistry: Aromatics, Carbonyls and Synthesis7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- 8Practical Skills and Data Analysis7 key notes, 100 flashcards, then 375 practice questions in 15 sets of 25Premium
- Final step: 6 full mock exams50 questions each, timed like exam day. Hit your target on them before your first paper.Premium
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Summarised from the exam boards' published specifications and the rules cited, checked November 2026. Confirm current requirements with AQA, OCR and Pearson Edexcel.