GCSE Chemistry revision (AQA, Edexcel, OCR)

Weigh the invisible: count protons, neutrons and electrons, place electrons in shells, follow the model of the atom from Dalton to Chadwick, then use the periodic table to predict how Groups 1, 7 and 0 behave — down to the transition metals.

See matter as particles: why solids hold shape, liquids flow and gases fill the room, how pure substances announce themselves through sharp melting and boiling points, and how chemists pick apart any mixture — by filter paper, evaporating dish, distillation column or chromatogram.

Three bonds explain almost every property you will be asked about: electrons transferred in ionic bonding, shared in covalent bonding, and pooled in metallic bonding. Learn the diagrams, the charges, the lattice and molecular structures — and why sodium chloride melts at 801 °C while methane manages −182 °C.

One element, four architectures: the same carbon atoms build the hardest natural solid, a slippery conductor, a one-atom sheet and hollow nanotubes — and, shrunk to nanoparticles, materials start behaving in ways bulk chemistry never predicted.

Chemistry’s bookkeeping: write and balance symbol equations, add state symbols, prove that no atom ever vanishes — even when a beaker seems to lose mass — and turn masses into empirical formulae and Mr values.

Chemistry counts particles it can never see: the mole bundles 6.02 × 10²³ of them into one package you can weigh. Master mol = mass ÷ Mr, ride the equation’s mole ratios to predict masses of products, spot the limiting reactant — and measure gases in 24 dm³ parcels.

How much stuff is dissolved in how much liquid? Weigh it for g/dm³, or — with a burette, a pipette and a drop of indicator — titrate it out to 0.05 cm³ precision and convert through moles to mol/dm³.

Every acid hands out H⁺ ions and every alkali hands out OH⁻ — put them together and neutral water plus a salt appear. Learn the pH logic, the strong/weak trap, the four acid reaction families, and the practical recipe chemists use to bottle a salt as pure dry crystals.

Rank every metal from fist-fighting potassium to gentle gold, then use the ranking twice: to predict who displaces whom, and to choose how each ore is won — carbon for the middling metals, electricity for the furious ones, and even plants and bacteria for the low-grade ores.

Electricity as a crowbar: push a current through a molten or dissolved ionic compound and it splits at the electrodes — metals at the cathode, non-metals at the anode. Learn the competition rules that decide aqueous products, the aluminium cell that runs on cryolite, and the half equations that score the Higher marks.

Every reaction pays an energy bill: bonds break (cost), bonds form (refund). When the refund beats the cost, heat floods out — exothermic. When the bill wins, heat drains in — endothermic. Learn to read reaction profiles, calculate ΔH from bond energies, and meet the cells that bottle the energy for later.

Reactions happen when particles collide hard enough. Every factor that speeds a reaction — hotter, more concentrated, finer powder, or a catalyst — works by making collisions more frequent or more energetic. Measure the fizz, read the graph, draw the tangent.

Some reactions run both ways. In a closed system they settle into a tug-of-war where forward and backward rates match — dynamic equilibrium. Change the conditions and the balance shifts to oppose you; industry exploits that with the Haber process, squeezing out ammonia under a compromise of heat, pressure and an iron catalyst.

Crude oil is bottled ancient plankton — a finite soup of hydrocarbons. Distillation sorts it into useful fractions by boiling point; combustion releases the energy; and cracking slices leftover long chains into the short alkenes industry is desperate for.

Three organic families built from the same small toolbox: –OH makes an alcohol, –COOH makes a weak acid, and C=C double bonds snap together into polymers. Learn the two routes to ethanol, why vinegar only weakly bites, and how monomers zip into plastics, polypeptides and DNA.

Chemists are detectives: chromatography pulls mixtures apart and measures Rf values, gas tests name what bubbles off, precipitate colours and flame colours name the ions, and spectroscopy does it all faster. Start with what "pure" really means — one substance, one sharp melting point.

Earth’s air is a four-billion-year story: volcanoes belched carbon dioxide, oceans drank most of it, and green plants topped the bottle up with oxygen. Learn the composition, how the greenhouse effect works and how it is being enhanced, what counts as evidence for climate change, and the pollutants combustion leaves behind.

Everything we use comes from Earth’s resources — so chemistry runs the supply chain: making water safe to drink, cleaning waste water, weighing a product’s whole life cycle, and designing alloys, ceramics and composites that resist rust and wear. Chemistry only sections cover the materials science.