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1. Chemistry 11–12 · Year 12

   Precipitation titration of chloride in seawater with silver nitrate and a chromate indicator (Mohr method)

   Silver ions precipitate chloride quantitatively, and the first excess of silver forms red-brown silver chromate, marking the end point so the chloride concentration can be found by titration.

   Practical, model not builtMedium risk

2. Chemistry 11–12 · Year 12

   Preparing a red cabbage indicator and mapping its colours across the pH scale

   An indicator is a weak acid whose acid and base forms differ in colour, so its colour reports the pH and changes reversibly as the pH is moved back and forth.

   PracticalMedium risk

3. Chemistry 11–12 · Year 12

   Preparing an ethanoic acid and ethanoate buffer and testing how it resists added acid and base

   A mixture of a weak acid and its conjugate base holds its pH when small amounts of acid or base are added, because the added ions are absorbed by the equilibrium between the two forms.

   Practical, model not builtMedium risk

4. Chemistry 11–12 · Year 12

   Reversible or not: copper(II) sulfate hydration, iron(III) thiocyanate, burning magnesium and burning steel wool

   Some changes can be driven back to the starting substances by reversing the conditions and some cannot; the difference decides whether a system can reach equilibrium.

   PracticalMedium risk

5. Chemistry 11–12 · Year 12

   Solubility rules from mixing ionic solutions, and predicting precipitates from Ksp

   Whether two ionic solutions give a precipitate follows a small set of solubility patterns, and quantitatively from comparing the ion product with the solubility product.

   Practical, model not builtMedium risk

6. Chemistry 11–12 · Year 12

   Substitution against addition: bromine water with cyclohexane in sunlight and in the dark

   An alkene takes up bromine at once and in the dark, because the double bond adds bromine directly, while an alkane takes up bromine only in light, because that reaction is a substitution which cannot begin until a photon splits a bromine molecule into two atoms. Light is therefore the variable that separates the two mechanisms.

   Practical, model not builtMedium risk

7. Chemistry 11–12 · Year 12

   Synthesising aspirin: percentage yield and purity by melting point

   An ester made in the school laboratory can be weighed against the mass its equation predicts, and its purity read from the temperature and the width of its melting range, so yield and purity become measured quantities with stated uncertainties rather than claims.

   Teacher-led demonstrationPractical, model not builtHigh risk

8. Chemistry 11–12 · Year 12

   Testing for carbon-carbon double bonds with bromine water and acidified permanganate on a microscale

   An alkene adds bromine across its double bond and decolourises bromine water at once, while an alkane needs light and time to substitute; the difference identifies unsaturation.

   PracticalMedium risk

9. Chemistry 11–12 · Year 12

   Testing organic unknowns for carbon-carbon double bonds, hydroxyl groups and carboxylic acids

   Three quick bench tests sort small organic molecules by functional group: bromine water for alkenes, an acidified oxidant for alcohols, and hydrogen carbonate for carboxylic acids.

   PracticalMedium risk

10. Chemistry 11–12 · Year 12

    The nylon rope trick (condensation polymerisation) with a model of addition and condensation polymer chains

    Monomers join into long chains either by adding across double bonds or by condensing with loss of a small molecule; the repeat unit fixes the chain's composition and the properties follow from the chain's structure.

    Teacher-led demonstrationPractical, model not builtHigh risk

11. Chemistry 11–12 · Year 12

    Titrating sodium hydroxide of unknown concentration against a standard acid

    The volume of a standard solution needed to reach the end point, with the mole ratio of the equation, fixes the unknown concentration to four significant figures.

    Practical, model not builtLow risk

12. Chemistry 11–12 · Year 12

    Titration curves with a pH probe and a conductivity probe: strong and weak acids against a strong base

    Logging pH and conductivity as base is added reveals the shape of the curve, the equivalence point, the buffer region of a weak acid and the pH at which an indicator must change.

    Practical, model not builtLow risk