GCSE Chemistry exam guide.

Timing strategy

• Budget about 1 minute per mark, leaving 5 minutes at the end to check calculations.
• Move fast through recall questions (definitions, test results, colours). They're quick marks if you know them.
• Multi-step calculations take longer. Moles and concentration questions may need 4–6 minutes; budget that in.
• Allow 6–8 minutes for 6-mark questions, planning the order of points first.
• If a calculation stalls, write what you can (the formula, the Mr) and come back. Early steps often score marks.

Showing working

• Write the equation first, then substitute values, then the answer with units. For example, moles = mass ÷ Mr.
• Show your Mr working (adding relative atomic masses) so you can still earn marks if you slip.
• Balance equations carefully and include state symbols when asked.
• Use error carried forward: if part (a) is wrong but you use it correctly in part (b), you can still earn the marks in (b). So always show the next step.
• Practical descriptions: give steps in order, with equipment and specific measurements ("25 cm³ using a pipette").
• Explain using particles, for example in bonding, rates and energy changes: particles collide more often, with more energy.

Calculator use

• Relative formula mass (Mr): add atomic masses from the periodic table, using brackets for groups like (OH)₂.
• Moles and mass: moles = mass ÷ Mr (Higher).
• Concentration: g/dm³ = mass ÷ volume. Convert cm³ to dm³ by dividing by 1,000.
• Percentage yield and atom economy: keep full values until the final answer.
• Rates: mean rate = quantity ÷ time; use a tangent for the rate at a specific time (Higher).
• Standard form for Avogadro's constant (6.02 × 10²³) and nanoparticle sizes.
• Significant figures: match the data given, and keep units throughout.

Revision checklist

• Atomic structure and the periodic table: atoms, isotopes, electron arrangement, groups 1, 7 and 0
• Bonding, structure and properties: ionic, covalent and metallic bonding, giant and simple structures
• Quantitative chemistry: Mr, conservation of mass, moles, concentration
• Chemical changes: reactivity series, acids and alkalis, salts, electrolysis
• Energy changes: exothermic and endothermic reactions, energy profiles, bond energies (Higher)
• Rate and extent of reaction: factors affecting rate, collision theory, equilibrium
• Organic chemistry: alkanes, alkenes, cracking, fractional distillation
• Chemical analysis: purity, formulations, chromatography, gas tests
• Chemistry of the atmosphere: greenhouse gases and climate change, pollutants
• Using resources: potable water, life cycle assessments, recycling
• Required practicals: method, variables and likely errors for each one
• Timed past papers, with calculation errors logged and redone

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