OCR A A-Level Chemistry revision

Work through OCR A in syllabus order. Each specification point has a short explanation, with equations, calculations and exam warnings where they help.

Start at the beginning or jump to the topic you need

The notes stay close to the OCR A course. Open a topic, check each line, then use the linked Chemistry Help questions when you want to test it.

Module 2: Foundations in Chemistry

2.1.1 Atomic structure and isotopes Use atomic number, mass number and ionic charge to count particles, then use isotope data and mass spectra to calculate relative masses. 2.1.2 Compounds, formulae and equations Predict ion charges, write ionic formulae, then balance full and ionic equations with the correct state symbols. 2.1.3 Amount of substance Use moles as the link between particles, masses, solutions and gases, then apply balanced-equation ratios to empirical formulae, yields and multi-step calculations. 2.1.4 Acids Recognise the common acids and alkalis, distinguish strong from weak acids, write neutralisation equations and use accurate titration technique and calculations. 2.1.5 Redox Assign oxidation numbers, use them in formulae and names, then track electron transfer and oxidation-state changes through redox reactions. 2.2.1 Electron structure Move from shells to orbitals and sub-shells, then build electron configurations and box diagrams for atoms and s- and p-block ions. 2.2.2 Bonding and structure Connect ionic and covalent bonding to structure, shape, polarity, intermolecular forces and the physical properties you can observe.

Module 3: Periodic Table and Energy

3.1.1 Periodicity Follow electron structure across the periodic table, then use it to explain ionisation energies, metallic and giant covalent structures, and melting-point trends. 3.1.2 Group 2 Use the ns² outer configuration to explain Group 2 ions, reactions and the increasing reactivity down the group, then apply the hydroxides and carbonates as bases. 3.1.3 The halogens Use electron structure and intermolecular forces to explain halogen trends, then work through displacement, disproportionation, water treatment and halide tests. 3.1.4 Qualitative analysis Use a short sequence of ion tests, observations and ionic equations to identify common anions and ammonium ions. 3.2.1 Enthalpy changes Read enthalpy signs and profiles, use standard enthalpy terms accurately, then calculate energy changes from calorimetry, bond enthalpies and Hess cycles. 3.2.2 Reaction rates Use collision theory, gradients and Maxwell–Boltzmann distributions to explain rates, then connect catalysts to activation energy and practical rate measurements. 3.2.3 Chemical equilibrium Distinguish dynamic equilibrium from equal concentrations, predict equilibrium shifts, and write and use Kc expressions for homogeneous equilibria.

Module 4: Core Organic Chemistry

4.1.1 Basic concepts of organic chemistry Get the language and drawing conventions secure first: names, formulae, isomers, bond fission and curly arrows turn up throughout organic chemistry. 4.1.2 Alkanes Connect alkane structure to shape, physical properties and low reactivity, then learn the radical-substitution chain mechanism. 4.1.3 Alkenes Use the C=C bond to explain alkene shape, E/Z isomerism and electrophilic addition, then connect addition reactions to polymers. 4.2.1 Alcohols Use hydrogen bonding to explain alcohol properties, then distinguish primary, secondary and tertiary alcohols and learn their main Year 12 reactions. 4.2.2 Haloalkanes Use the polar C–X bond to explain nucleophilic substitution and hydrolysis rates, then connect radical chemistry to ozone depletion. 4.2.3 Organic synthesis Choose the right apparatus and purification sequence, then connect functional groups into short OCR Year 12 synthetic routes. 4.2.4 Analytical techniques Use IR and mass spectra as evidence: identify characteristic bonds, read molecular mass and fragments, then make one structure that fits all the data.