Revision sheets

Short sheets to read the night before the test: the essentials to know by heart, the method in the order that works, and the mistakes that cost the most marks.

Middle school15

Matter and measurement

Middle school8′States of matter and phase transitionsThe three states, the six phase transitions and their names, and why temperature holds steady during a plateau.7 points to remember Middle school8′Mass, volume and densityThe formula ρ = m/V and its two rearrangements, the unit conversions that cost marks, and how to predict whether an object floats or sinks.8 points to remember Middle school8′Mixtures and solutionsHomogeneous or heterogeneous, solute or solvent, saturation — and above all which technique separates which mixture.8 points to remember Middle school7′Mass concentrationThe formula Cm = m/V, the mL → L conversion that costs the most marks, and how it differs from density.7 points to remember

Atoms and molecules

Middle school6′The simplified model of the atomNucleus, protons, neutrons, electrons: which carries which charge, why the atom is neutral, and what the atomic number tells you.7 points to remember Middle school7′Atoms, molecules and ionsThree words that get mixed up: tell them apart at a glance from a formula, and know where an ion's charge comes from.7 points to remember Middle school7′Chemical symbols and formulasCapital, lowercase, subscript, coefficient: the four writing rules, and the method for counting atoms without slipping.7 points to remember

Chemical transformations

Middle school8′Reactants and products of a chemical changeRecognise a chemical change, name what disappears and what appears, and the two identification tests to know.7 points to remember Middle school6′Conservation of massLavoisier's law, why it holds (atoms do not vanish), and how to use it to find a missing mass.7 points to remember Middle school9′Balancing a chemical equationThe one rule — change coefficients, never subscripts — and a step-by-step method for balancing without guesswork.8 points to remember Middle school7′CombustionThe fire triangle, the difference between complete and incomplete combustion, and why carbon monoxide kills without warning.7 points to remember

Electricity and chemistry

Middle school6′Electrical conduction in solutionsWhy salt water conducts and sugar water does not: ions carry the current, not the mere fact of being dissolved.7 points to remember Middle school8′Ions and their chargeWork out an ion's charge from its protons and electrons, and write an ionic formula that respects neutrality.9 points to remember

Toward high school

Middle school8′The mole: counting matter in batchesThe mole, the Avogadro constant, a molecule's molar mass and the relation n = m/M — the foundation for all of high-school chemistry.8 points to remember Middle school7′A first look at the periodic tablePeriods, groups, four families to know — and how an element's column announces the ion it forms.9 points to remember

High school33

Constitution of matter

High school9′Atomic structure: from shells to orbitalsK, L, M shells, the valence shell, orbitals and quantum numbers: distribute an atom's electrons from Z without falling into the potassium trap.9 points to remember High school11′Writing an electron configurationKlechkowski, Pauli, Hund: write the configuration of an atom and then of its ion, count valence electrons, and stop getting copper and iron(II) wrong.9 points to remember High school10′Finding your way around the periodic tablePeriod, group, block, family: place any element in the table from Z and work out its chemical behaviour from there.9 points to remember High school10′Periodic trends: radius, ionisation, electronegativityCompare two elements without a data table: atomic radius, ionisation energy and electronegativity follow from effective charge and the number of shells.9 points to remember High school10′Covalent bonding and Lewis structuresBuild a Lewis structure without guesswork: count the valence electrons, place the pairs, switch to multiple bonds and check with formal charge.9 points to remember High school10′Ionic bonding and ionic solidsFrom electron transfer to crystal: write the formula of an ionic solid, understand where its stability comes from and predict its properties.9 points to remember High school8′Metallic bonding and the properties of metalsOne model — positive ions in a sea of electrons — to explain why a metal conducts, shines, bends without breaking and melts at a higher or lower temperature.9 points to remember High school10′Molecular geometry: the VSEPR methodGo from the Lewis structure to the three-dimensional shape: count the directions around the central atom, name the geometry, give the angle and conclude on polarity.9 points to remember

Amount of substance and solutions

High school12′The mole and amount of substanceThe four relations that give an amount of substance, how to pick the right one, and the unit traps that cost the most marks.7 points to remember High school10′Molar concentration and preparing a solution from a solidC = n/V without picking the wrong volume, the mass to weigh for a volumetric flask, and going from a label's g/L or % to mol/L.9 points to remember High school9′Diluting a solution: dilution factor and protocolThe one idea to hold on to — the amount of solute does not change —, working out the volume to pipette, the right glassware and serial dilutions.9 points to remember High school12′Stoichiometry: limiting reactant, extent of reaction and yieldFrom the balanced equation to the mass of product: finding the limiting reactant without being fooled, reading the progress table and applying a yield.9 points to remember

Chemical transformations

High school10′Brønsted acids and bases: pairs, Ka and pKaSpot an acid/base pair, write a reaction as a proton transfer and tell from the pKa values whether it is favoured.9 points to remember High school11′Calculating a pH: strong acid, weak acid, baseGo from concentration to pH and back, pick the right formula for the strength of the acid or base, and check the assumption you made.9 points to remember High school15′Balancing a redox half-equationThe five-step method, in the order that actually works, and how to combine two half-equations without leaving electrons behind.7 points to remember High school11′Precipitation: solubility product and the Q vs Ksp testWrite a solubility product, turn it into a solubility, and decide by calculation whether a precipitate appears when two solutions are mixed.9 points to remember High school10′Complexes: ligands, formation constant and redissolving a precipitateWrite the formula and charge of a complex, set up its formation constant, and explain why a precipitate vanishes in excess ligand.9 points to remember High school11′Chemical equilibrium: Q, K and the equilibrium compositionWrite a reaction quotient, predict the direction of change by comparing Q with K, and compute an equilibrium composition with an ICE table.8 points to remember High school10′Le Chatelier's principle: predicting how an equilibrium shiftsConcentration, pressure, temperature, catalyst: tell which way the equilibrium shifts, what happens to K, and make sense of the Haber-Bosch trade-offs.9 points to remember

Thermochemistry and kinetics

High school10′Energy of a reaction: exothermic, endothermic, bond energiesTell an exothermic reaction from an endothermic one, and estimate its energy balance by counting bonds broken and formed, without getting the sign wrong.9 points to remember High school11′Reaction enthalpy: enthalpies of formation, Hess's law, calorimetryCalculate a standard reaction enthalpy from enthalpies of formation, combine equations using Hess's law and work up a calorimeter measurement.9 points to remember High school10′Reaction rate: defining it, measuring it, changing itCalculate an average or instantaneous rate from a curve without losing the sign or the coefficient, choose a monitoring method and name the factors that speed things up.9 points to remember High school12′Rate laws, reaction orders and half-lifeRecognise order 0, 1 or 2 from measurements, extract the rate constant and the half-life, and use the Arrhenius equation without unit traps.9 points to remember High school9′Catalysis: what a catalyst changes, and what it does notSpot a catalyst in a mechanism, tell homogeneous, heterogeneous and enzymatic catalysis apart, and read an energy profile without confusing the barrier with the balance.9 points to remember

Organic chemistry

High school9′Carbon skeletons: chains, names and isomersRecognise a saturated, branched or cyclic chain, name a branched alkane without picking the wrong chain, and find the isomers of a molecular formula.9 points to remember High school9′Recognising and naming functional groupsThe eight families to spot at a glance, the one question that separates aldehyde, ketone, acid and ester, and the suffix that goes with each.9 points to remember High school10′Alcohols, aldehydes and ketones: controlled oxidationClassify an alcohol in ten seconds, predict what its controlled oxidation gives, and tell an aldehyde from a ketone with Fehling's solution.9 points to remember High school11′Carboxylic acids, esters and soapsWrite an esterification, name the ester without swapping its two halves, calculate a yield, and know why saponification, unlike it, goes to completion.9 points to remember High school9′Addition, substitution, elimination: classifying a reactionThree categories, two questions to tell them apart — how many species, what happens to the double bond — and Markovnikov's rule for placing the H.9 points to remember High school10′Stereoisomerism: Z/E, asymmetric carbon, enantiomersSpot an asymmetric carbon or a Z/E double bond in a structural formula, and say whether two molecules are enantiomers or diastereomers.9 points to remember

Toward undergraduate chemistry

High school10′Atomic orbitals: quantum numbers and fillingThe four quantum numbers, how many orbitals per subshell, and the method for writing an electron configuration with its orbital boxes.9 points to remember High school12′IR and proton NMR spectra: identifying a moleculeThe IR bands to recognise, then the four pieces of information in an NMR spectrum — signals, integrals, shift, multiplicity — in the order you use them.9 points to remember High school11′Reaction mechanisms: curved arrows, SN2 and SN1Where a curved arrow starts and where it lands, the difference between an intermediate and a transition state, and what sets SN2 apart from SN1.9 points to remember

University38

Advanced atomistics

University12′The quantum atom: wavefunction, quantum numbers, energyThe de Broglie relation, the meaning of |ψ|², the bounds of the four quantum numbers and hydrogen-like energies: the base of every atomic-structure problem.9 points to remember University11′s, p, d, f orbitals: shapes, nodes and countingGo from an orbital's name to its quantum numbers, shape and nodes, and count the orbitals and electrons of a subshell without hesitation.9 points to remember University13′Spin-orbit coupling and term symbolsFind an atom's ground term with Hund's rules, read a term symbol and understand where the yellow sodium doublet comes from.9 points to remember University12′Atomic spectra: levels, lines and the Rydberg formulaCompute the wavelength of a hydrogen line along two routes, place it in its series and say whether the transition is allowed.9 points to remember

Bonding and molecules

University11′Advanced Lewis: formal charges, resonance, hypervalenceCompute a formal charge, choose between two Lewis structures, put a number on a resonance bond order and recognise the three exceptions to the octet.9 points to remember University11′VSEPR: predicting shapes with AXnEmGo from the Lewis structure to the AXnEm label, then to shape and angles: arrangement, where lone pairs sit, departures from the ideal angles.9 points to remember University10′Hybridisation: sp, sp², sp³ and σ/π bondsAssign sp, sp² or sp³ to any atom by counting its domains, then tally the σ and π bonds of a molecule without missing any.9 points to remember University13′Molecular orbitals: LCAO and second-period diatomicsFill the MO diagram of a diatomic, pick the right σ/π ordering for the molecule, compute the bond order and predict magnetism — O₂ included.9 points to remember University12′MO diagrams: bond order, bond length, magnetismRead an MO diagram to predict what ionisation does to a bond: bond order, length, energy and magnetic moment, from O₂⁺ to peroxide.9 points to remember

Chemical thermodynamics

University11′First law and reaction enthalpyThe signs of Q and W, going from ΔU to ΔH, and Hess's law applied the right way round: compute a reaction enthalpy without dropping marks.9 points to remember University11′Second law and entropyPredict the sign of an entropy change, compute it (tables or reversible Q over T) and settle spontaneity with the system + surroundings balance.9 points to remember University11′Gibbs energy and spontaneityCompute ΔG = ΔH − TΔS without falling into the units trap, read the four sign cases and find the temperature at which a reaction tips over.9 points to remember University12′Equilibrium constant, reaction quotient and van 't HoffWrite K with activities, go from ΔrG° to K without a units slip, compare Q with K to predict the direction, and track K with temperature via van 't Hoff.9 points to remember

Advanced kinetics

University11′Complex mechanisms: from elementary steps to the rate lawSpot the intermediate and the slow step, handle a fast pre-equilibrium, and turn a mechanism into a rate law that can be tested against experiment.9 points to remember University13′The steady-state approximation: deriving a rate law cleanlySet d[I]/dt ≈ 0 without slipping on a sign or a factor of 2, and recover step by step the rate law of H₂ + Br₂, of order 3/2 at the start.9 points to remember University11′Homogeneous catalysis: reading a catalytic cycleWhat a catalyst does and does not change, the gain worked out with Arrhenius, and the Wilkinson cycle read step by step: oxidation state, electrons, name.9 points to remember University12′Heterogeneous catalysis and the Langmuir isothermThe five steps of a surface cycle, the Langmuir isotherm and its two regimes (first order, zero order), and how to extract K from adsorption measurements.9 points to remember University13′Enzyme kinetics: Michaelis-Menten and Lineweaver-BurkThe Michaelis-Menten equation and what Km and Vmax really mean, the Lineweaver-Burk line read without slips, and the signature of each type of inhibition.9 points to remember

Electrochemistry

University12′Galvanic or electrolytic cell: electrodes, terminals and Faraday's lawName the anode and cathode without getting the sign wrong, link emf to Gibbs energy, and compute a deposited mass from a current and a duration.9 points to remember University11′Standard potentials: predicting a redox reactionRead a scale of standard potentials, apply the gamma rule and compute a standard emf without slipping on a sign or a coefficient.9 points to remember University13′Nernst equation: from standard potential to actual potentialWrite Nernst for any couple, compute the emf of a cell away from standard conditions and derive an equilibrium constant from it.9 points to remember University13′Potential-pH diagrams: boundaries, slopes and corrosionRecognise the three kinds of boundary, derive a slope from the half-equation, and tell whether a metal is immune, corroding or passivated.9 points to remember

Advanced organic chemistry

University12′Stereochemistry: assigning R/S and Z/ERank substituents with the CIP rules, duplicated multiple bonds included, then read R or S and Z or E without getting the direction wrong.9 points to remember University13′SN1, SN2, E1, E2: choosing the mechanismFour criteria — substrate, reagent, solvent, temperature — to predict the mechanism for a haloalkane, then the stereochemistry and the major alkene.9 points to remember University12′Aromaticity and electrophilic aromatic substitutionCount π electrons to apply Hückel's rule, then predict where the electrophile goes: ortho/para or meta, and why.9 points to remember University11′Multi-step synthesis and retrosynthesisWork back from a target to its precursors by disconnections, order the steps, protect what needs protecting and put a number on the overall yield.9 points to remember

Inorganic chemistry

University12′Crystal field: splitting, spin and CFSECount a complex's d electrons, place them in t2g and eg, decide between high spin and low spin, then work out the CFSE and link colour to Δo.9 points to remember University10′Transition metals: configurations and oxidation statesWrite the configuration of a 3d metal and its ions without slips, find an oxidation state in an oxoanion, and predict a redox reaction from standard potentials.9 points to remember University11′Organometallics: counting to 18 electronsCount a complex's valence electrons without mixing conventions, spot 16- and 17-electron species, and read back-donation from an IR spectrum.9 points to remember University13′Crystallography: cubic cells and densityCount the formula units in a cell, link the parameter a to the atomic radius, recover the packing fractions 0.52 / 0.68 / 0.74 and calculate a crystal's density.9 points to remember

Spectroscopic methods

University12′IR and UV-visible: reading a spectrum, quantifying with Beer-LambertThe IR bands to spot at a glance, a routine for reading a spectrum from left to right, and the Beer-Lambert law without unit mistakes.9 points to remember University13′¹H and ¹³C NMR: from spectrum to structureChemical shift, integration, the n+1 rule: the three readings of a ¹H spectrum, in order, to work back to the structure without guesswork.9 points to remember University12′Mass spectrometry: molecular ion, isotopes, fragmentsFind the molecular ion, recognise a chlorine or a bromine from its isotope pattern, and make the fragments talk — in that order.9 points to remember University10′X-ray diffraction: Bragg's law in practiceBragg's law, the 2θ angle trap, and the method for going from a diffractogram peak to an interplanar spacing, then to the unit-cell parameter.9 points to remember

Toward graduate work

University12′Computational quantum chemistry: choosing a level of theoryPick a functional and a basis set sensibly, read a calculation output and convert hartrees into kJ/mol to compare two structures.9 points to remember University14′Group theory: finding a molecule's point groupThe flowchart that leads to the point group, the C2v character table, the reduction formula and the IR and Raman selection rules.9 points to remember University12′Supramolecular chemistry: analysing a host-guest assemblySpot the non-covalent interactions in an assembly, judge host-guest complementarity and go from the association constant to the energy.9 points to remember University12′Green chemistry and asymmetric catalysis: putting numbers on a synthesisWork out an atom economy, an E-factor, a PMI and an enantiomeric excess, and know what a catalyst changes — and what it does not.9 points to remember