Options: Applying Core Chemistry to a Chosen Context
In Paper 3 Section B you answer questions on one of four options: Materials, Biochemistry, Energy or Medicinal chemistry. The option is not isolated facts to memorise; it tests your ability to apply core ideas-bonding, equilibrium, kinetics, organic functional groups and energetics-to a specific context.
Core rules and concepts
- Know the specified content and contexts of your option. Typical examples: Materials (polymers, alloys, unit cells, density, structure–property links); Biochemistry (amino acids, proteins, enzymes, carbohydrates, DNA); Energy (fuels, fuel cells, energy density, efficiency); Medicinal chemistry (drug action, aspirin, penicillin, chirality, solubility).
- Practise data interpretation from tables and graphs, and multi-step calculations using core formulas.
- Be able to draw and interpret structures, and explain structure–property relationships using bonding and intermolecular forces.
- Use correct terminology and units, and show working in calculations.
- Link the context back to core principles rather than giving a vague contextual description.
Worked example
Calculate the atom economy for aspirin synthesis: salicylic acid (M = 138.12) + acetic anhydride (M = 102.09) → aspirin (M = 180.16) + acetic acid (M = 60.05). Atom economy = (molar mass of desired product / total molar mass of reactants) × 100 = 180.16 / (138.12 + 102.09) × 100 = 75.0%. The reasoning shows that atom economy compares the mass of desired product with the total reactant mass; a higher value indicates a greener process. Do not confuse atom economy with percentage yield.
Traps that cost marks
Do not give a generic core answer that ignores the option context. Do not confuse atom economy with percentage yield. Do not omit units in energy density or efficiency calculations. Do not confuse empirical and molecular formulas when interpreting structures. Do not forget that chirality affects drug action in medicinal chemistry.