Chemistry revision notes

Calm, exam-focused notes for revising on your own.

Edexcel International A Level Chemistry

  1. Topic 1: Formulae, Equations and Amount of Substance

    The toolkit for the whole course. Every calculation you will ever do in chemistry runs through one quantity, the amount of substance in moles.

    1. Particles and formulae
    2. Relative mass and the mole
    3. Writing equations
    4. Masses from equations
    5. Solutions and parts per million
    6. Gas volumes
    7. Core Practical 1: molar volume of a gas
    8. Yield and atom economy
    9. Formulae and equations by experiment
    10. Test-tube reactions
    11. Topic 1 on a page
  2. Topic 2: Atomic Structure and the Periodic Table

    What is inside an atom, how we know, and how the answer explains the shape of the Periodic Table and the pattern of properties across a period.

    1. Inside the atom
    2. Isotopes
    3. The mass spectrometer
    4. Relative atomic mass from mass spectra
    5. Molecules and 2+ ions
    6. Predicting spectra of diatomic molecules
    7. Ionisation energy
    8. Successive ionisation energies
    9. First ionisation energy of elements 1 to 36
    10. Orbitals, sub-shells and shells
    11. Filling the orbitals
    12. Potassium to krypton, and ions
    13. Blocks of the Periodic Table, and why configuration matters
    14. Explaining ionisation energy trends
    15. Melting and boiling temperatures of Periods 2 and 3
    16. Topic 2 on a page
  3. Topic 3: Bonding and Structure

    How atoms hold together, and how the type of bonding and the shape of the particles explain melting temperatures, conduction, hardness, polarity and the shapes of molecules.

    1. Ions and electron transfer
    2. Giant ionic lattices and ionic bonding
    3. Evidence for ions
    4. Migration of ions
    5. Ionic radius and bond strength
    6. Polarisation
    7. Covalent bonds and dot-and-cross diagrams
    8. Dative covalent bonds
    9. Giant covalent structures and carbon
    10. Electronegativity and bond polarity
    11. Electron-pair repulsion theory
    12. Shapes with no lone pairs
    13. Lone pairs and the shapes of NH3 and H2O
    14. Polar bonds and polar molecules
    15. Metallic bonding
    16. Topic 3 on a page
  4. Topic 4: Introductory Organic Chemistry and Alkanes

    The language of organic chemistry (hazards, families, formulae, names, reaction types, bond breaking) and the first family, the alkanes. Their isomers, their use as fuels, their combustion and the free radical substitution mechanism.

    1. Hazard and risk
    2. Homologous series and functional groups
    3. Ways of writing a formula
    4. Naming organic compounds
    5. Types of organic reaction
    6. Bond breaking, free radicals and electrophiles
    7. Alkanes and cycloalkanes
    8. Structural isomerism
    9. Isomers of alkanes and cycloalkanes
    10. Crude oil and fractional distillation
    11. Cracking and reforming
    12. Combustion of alkanes
    13. Pollutants from burning fuels
    14. Alternative fuels and carbon neutrality
    15. Alkanes and halogens
    16. Free radical substitution: the mechanism
    17. Further substitution and its limits
    18. Topic 4 on a page
  5. Topic 5: Alkenes

    The first unsaturated family. The C=C double bond fixes the shape of the molecule, gives geometric isomers, and makes alkenes react by addition, with a mechanism you can draw. Alkenes also join to make polymers.

    1. Alkenes and the double bond
    2. Restricted rotation around C=C
    3. Which alkenes have geometric isomers
    4. E–Z naming
    5. Adding hydrogen and halogens
    6. Adding hydrogen halides and steam
    7. Oxidation to a diol and the bromine test
    8. Electrophiles and curly arrows
    9. The mechanism for ethene and bromine
    10. The mechanism for ethene and hydrogen bromide
    11. Carbocation stability
    12. The mechanism for propene and hydrogen bromide
    13. Addition polymerisation
    14. From monomer to repeat unit, and back
    15. Polymer disposal
    16. Topic 5 on a page
  6. Topic 6: Energetics

    Chemical reactions move heat between the chemicals and their surroundings. This topic gives that heat a name, a sign and a number, shows how to measure it, and shows how to work it out when it cannot be measured.

    1. Enthalpy change and its sign
    2. Enthalpy level diagrams
    3. Enthalpy changes of reaction and formation
    4. Enthalpy changes of combustion, neutralisation and atomisation
    5. Measuring the energy transferred
    6. From joules to kJ mol⁻¹
    7. Errors, uncertainty and assumptions
    8. Graphs and cooling-curve corrections
    9. Hess's Law and enthalpy cycles
    10. Hess cycles from formation and combustion data
    11. Core Practical 2: method
    12. Core Practical 2: results, cycle and evaluation
    13. Bond enthalpies and enthalpy changes
    14. Limits of bond enthalpy calculations, and finding a mean bond enthalpy
    15. Which bond breaks first?
    16. Topic 6 on a page
  7. Topic 7: Intermolecular Forces

    Molecules attract each other with three kinds of force, in order of strength. This topic names them, shows how to spot each one, and uses them to explain boiling temperatures, the strange properties of water, and what dissolves in what.

    1. Forces between molecules
    2. London forces
    3. Alkane chains and branching
    4. Permanent dipole–permanent dipole interactions
    5. Hydrogen bonds
    6. Predicting hydrogen bonding
    7. Why water melts and boils so high
    8. Why ice floats
    9. Alcohols against alkanes
    10. The hydrogen halides
    11. Water as a solvent for ionic compounds
    12. Alcohols and halogenoalkanes in water
    13. Non-aqueous solvents
    14. Putting the forces together
    15. Topic 7 on a page
  8. Topic 8: Redox Chemistry and Groups 1, 2 and 7

    Redox is the movement of electrons, tracked with oxidation numbers. This topic uses it to explain the metals of Groups 1 and 2 and the halogens of Group 7, and then adds the tests and titrations that identify their compounds.

    1. Oxidation number and the rules
    2. Calculating oxidation numbers
    3. Roman numerals and writing formulae
    4. Oxidation and reduction
    5. Oxidising and reducing agents
    6. Building half-equations
    7. Full ionic equations
    8. Disproportionation and classifying reactions
    9. Ionisation energy and reactivity down Groups 1 and 2
    10. Reactions of Group 1 and 2 metals
    11. Oxides and hydroxides of Groups 1 and 2
    12. Solubility of Group 2 hydroxides and sulfates
    13. Thermal stability: size and charge of the cation
    14. Decomposing carbonates and nitrates
    15. Flame colours and electron transitions
    16. Tests for carbonate, hydrogencarbonate and sulfate ions
    17. Ammonium ions and identifying an unknown salt
    18. Concentration and titration
    19. Titration calculations
    20. Core Practical 3: concentration of hydrochloric acid
    21. Core Practical 4: a standard solution from a solid acid
    22. Measurement uncertainty in volumetric analysis
    23. Trends in Group 7
    24. Colours of the halogens and displacement reactions
    25. Halogens with metals, and chlorine with water
    26. Chlorine with alkali: bleach and chlorate(V)
    27. Halides with concentrated sulfuric acid
    28. Silver nitrate test and hydrogen halides
    29. Predicting fluorine and astatine
    30. Topic 8 on a page
  9. Topic 9: Introduction to Kinetics and Equilibria

    Two questions about any reaction. How fast does it go, and how far? Kinetics answers the first with collisions and activation energy, and equilibrium answers the second with Le Chatelier. Industry has to balance both.

    1. Measuring rate with time
    2. Rate from the gradient of a tangent
    3. Rate practicals
    4. Collisions and activation energy
    5. Concentration, pressure and surface area
    6. The Maxwell–Boltzmann distribution
    7. Temperature and the curve
    8. Catalysts and reaction profiles
    9. Catalysts and the Maxwell–Boltzmann curve
    10. Catalysts in industry
    11. Reversible reactions and dynamic equilibrium
    12. Le Chatelier — concentration and pressure
    13. Temperature, catalysts and writing the justification
    14. Yield, rate and the industrial compromise
    15. Evaluating data on yield and rate
    16. Topic 9 on a page
  10. Topic 10: Organic Chemistry: Halogenoalkanes, Alcohols and Spectra

    Ethane ignores hydroxide, bromoethane does not. This topic explains why, uses the answer on halogenoalkanes and alcohols, and ends with the question every preparation asks: did we make what we meant to make?

    1. Seven types of reaction
    2. Mechanisms and curly arrows
    3. Nucleophiles, electrophiles and bond polarity
    4. Naming and drawing halogenoalkanes
    5. Primary, secondary and tertiary halogenoalkanes
    6. Hydroxide: substitution or elimination
    7. Ammonia and cyanide
    8. Water as the nucleophile
    9. Mechanism: hydroxide and a primary halogenoalkane
    10. Mechanism: ammonia and a primary halogenoalkane
    11. Rates of hydrolysis: primary, secondary, tertiary
    12. Rates of hydrolysis: chloro, bromo, iodo
    13. Core Practical 5: method
    14. Core Practical 5: results and conclusion
    15. Naming and classifying alcohols
    16. Burning alcohols and losing water
    17. Replacing the OH group with a halogen
    18. Heating under reflux and distillation
    19. Separating, drying and checking a liquid
    20. Core Practical 6: chlorination of 2-methylpropan-2-ol
    21. Oxidation of alcohols
    22. Distil to stop, reflux to go on
    23. Telling the products apart
    24. Core Practical 7: propan-1-ol to propanal and propanoic acid
    25. Mass spectra
    26. Infrared spectra
    27. Identifying an unknown
    28. Topic 10 on a page
  11. Topic 11: Kinetics

    Turns "faster" and "slower" into numbers. A rate equation says how the rate depends on concentration, the orders come from experiment, and the equation points to the slow step in the mechanism.

    1. Rate, rate equation and order
    2. The rate constant and its units
    3. Half-life
    4. Activation energy and catalysts
    5. Choosing a technique to follow a reaction
    6. Initial rates and continuous monitoring
    7. Orders from initial-rate data
    8. Orders from concentration–time graphs
    9. Orders from rate–concentration graphs
    10. The rate-determining step and the rate equation
    11. Iodination of propanone: data and predictions
    12. Deducing a mechanism
    13. Primary halogenoalkanes: the SN2 evidence
    14. Tertiary halogenoalkanes: the SN1 evidence
    15. Activation energy from a graph
    16. Activation energy by calculation
    17. Solid catalysts in industry
    18. Core Practical 9a: iodine and propanone by titration, method
    19. Core Practical 9a: results and evaluation
    20. Core Practical 9b: the iodine clock, method
    21. Core Practical 9b: results, order and activation energy
    22. Topic 11 on a page
  12. Topic 12: Entropy and Energetics

    Two questions about energy that enthalpy alone cannot answer. Why do endothermic changes happen, and how strong is the bonding inside an ionic solid? The first is answered by entropy, the second by lattice energy.

    1. Enthalpy is not enough
    2. Entropy and dispersal
    3. Entropy of substances
    4. Why entropy changes
    5. Entropy change of the system
    6. Surroundings and total entropy
    7. Balance and temperature
    8. The feasibility temperature
    9. Thermodynamic and kinetic stability
    10. Three definitions for ionic solids
    11. Building a Born-Haber cycle
    12. Born-Haber calculations
    13. Covalent character in ionic bonds
    14. Enthalpy of solution and hydration
    15. Charge and radius
    16. Will it dissolve?
    17. Group 2 solubility trends
    18. Topic 12 on a page
  13. Topic 13: Chemical Equilibria

    The equilibrium constant turns the Unit 2 rule about which way an equilibrium shifts into a single number. You write it, calculate it, and learn that only temperature changes it, because of entropy.

    1. Writing Kc
    2. Partial pressures and Kp
    3. Heterogeneous systems
    4. Units of K
    5. Kc from equilibrium amounts
    6. Kc from a titration
    7. Calculating Kp
    8. What changes K
    9. Pressure and catalysts
    10. Temperature changes K
    11. Entropy and K
    12. How far does it go
    13. Topic 13 on a page
  14. Topic 14: Acid-base Equilibria

    Two acids at the same concentration can have very different pH. This topic puts numbers on that difference with pH, Ka and Kw, then uses titration curves and buffers to control and measure it.

    1. Acids, bases and conjugate pairs
    2. pH and hydrogen ion concentration
    3. Strong and weak acids
    4. The acid dissociation constant
    5. pH of a weak acid
    6. Ka from a measured pH
    7. Water and strong bases
    8. Measuring pH and dilution
    9. Reading a titration curve
    10. Four monoprotic curves
    11. Diprotic acids and bases
    12. Choosing an indicator
    13. What a buffer is and how it works
    14. pH of a buffer
    15. Making a buffer of a given pH
    16. Buffers on the titration curve
    17. Buffers in blood, cells and food
    18. Core Practical 11: finding the Ka of a weak acid
    19. Topic 14 on a page
  15. Topic 15: Organic Chemistry: Carbonyls, Carboxylic Acids and Chirality

    Mirror-image molecules, the C=O group and everything built on it, and the spectra and chromatography that prove what you have made.

    1. Chiral centres
    2. Drawing enantiomers
    3. Optical activity and racemic mixtures
    4. Optical activity as evidence for a mechanism
    5. Naming aldehydes and ketones
    6. Physical properties of carbonyl compounds
    7. Oxidation tests for aldehydes
    8. Reducing carbonyl compounds with LiAlH₄
    9. Addition of hydrogen cyanide
    10. 2,4-DNPH and the iodoform test
    11. Practical, identifying carbonyl compounds
    12. Naming carboxylic acids
    13. Hydrogen bonding in carboxylic acids
    14. Making carboxylic acids
    15. Reactions of carboxylic acids
    16. Esterification
    17. Naming acyl chlorides and esters
    18. Reactions of acyl chlorides
    19. Hydrolysis of esters
    20. Polyesters
    21. Accurate relative molecular mass
    22. Carbon-13 NMR
    23. Proton NMR, environments and peak areas
    24. Splitting and the (n + 1) rule
    25. Predicting and deducing from proton NMR
    26. Chromatography and Rf values
    27. Column chromatography
    28. Putting the data together
    29. Topic 15 on a page
  16. Topic 16: Redox Equilibria

    Redox reactions move electrons, and the voltage of a cell measures how strongly they are pushed. This topic turns that voltage into predictions, titration results and fuel cells.

    1. Oxidation and reduction
    2. Building redox equations
    3. From a reaction to a cell
    4. The standard hydrogen electrode and half-cells
    5. The electrochemical series
    6. Cell emf and cell diagrams
    7. Core Practical 12: electrochemical cells
    8. Why the conditions matter
    9. Predicting feasibility
    10. Cell emf, entropy and the equilibrium constant
    11. Limits of predictions from standard potentials
    12. Disproportionation
    13. Redox titration reactions and ratios
    14. Core Practical 13a: iron(II) with manganate(VII)
    15. Core Practical 13b: sodium thiosulfate and iodine
    16. Redox titration calculations
    17. Uncertainty and validity
    18. Fuel cells
    19. The hydrogen-oxygen fuel cell
    20. Topic 16 on a page
  17. Topic 17: Transition Metals and their Chemistry

    Why d-block metals are special, how their ions form coloured complexes with ligands, and how the same electrons that give variable oxidation numbers make them good catalysts.

    1. Transition metals and their electrons
    2. Variable oxidation number
    3. Ligands and complex ions
    4. Shapes of complex ions
    5. Bidentate and hexadentate ligands
    6. Why complexes are coloured
    7. No colour, and changes of colour
    8. Vanadium: four oxidation states
    9. Chromium: reduction and oxidation
    10. Chromate(VI) and dichromate(VI)
    11. Three reactions of aqua ions
    12. Eight ions with sodium hydroxide
    13. Eight ions with ammonia
    14. Ligand exchange and colour
    15. Stability and entropy
    16. Haemoglobin and carbon monoxide
    17. Core Practical 14: preparing a transition metal complex
    18. Two kinds of catalyst
    19. V₂O₅ and catalytic converters
    20. Homogeneous catalysis in solution
    21. Topic 17 on a page
  18. Topic 18: Organic Chemistry – Arenes

    Benzene is a ring of six carbon atoms sharing six delocalised electrons. That one idea explains why it is unusually stable, why it resists addition, and why it reacts by electrophilic substitution instead.

    1. Benzene and the energy evidence
    2. Bond lengths and infrared evidence
    3. The delocalised model
    4. Why benzene resists bromination
    5. Reactions of benzene at a glance
    6. Electrophilic substitution and bromination
    7. Nitration and sulfonation
    8. Friedel-Crafts reactions
    9. Phenol and bromine water
    10. Uses and exam technique
    11. Topic 18 on a page
  19. Topic 19: Organic Nitrogen Compounds: Amines, Amides, Amino Acids and Proteins

    Amines, amides, amino acids and the polymers built from them. One atom, nitrogen, with one lone pair, explains the base behaviour, the reactions and the shapes of the molecules in this topic.

    1. Names and formulae
    2. Amines and water
    3. Salts and complex ions
    4. Making and extending amines
    5. Acyl chlorides and amides
    6. Phenylamine and azo dyes
    7. Polyamides and proteins
    8. Addition polymers
    9. Hydrogen bonding in polymers
    10. Amino acids as acids and bases
    11. Amino acids and polarised light
    12. Peptide bonds
    13. Routes and exam technique
    14. Topic 19 on a page
  20. Topic 20: Organic Synthesis

    The topic that pulls the whole organic course together. Work out what an unknown compound is from data, build a bigger molecule from a smaller one, plan a route of up to four steps, and prepare and purify a product in the laboratory.

    1. Formulae from combustion and composition
    2. Tests for functional groups
    3. Infrared and mass spectra
    4. NMR: environments, shifts and areas
    5. NMR splitting and solving structures
    6. Grignard reagents and carbon dioxide
    7. Grignard reagents and carbonyl compounds
    8. Unfamiliar compounds
    9. The reaction map
    10. Planning a route
    11. Reflux, washing and solvent extraction
    12. Drying, distillation and steam distillation
    13. Recrystallisation, melting and boiling temperatures
    14. Choosing a procedure and controlling risk
    15. Core Practical 16: preparing aspirin
    16. Topic 20 on a page