Specification references covered: C2.8 (choosing appropriate separation technique); C2.12 (sedimentation, filtration, chlorination; seawater distillation; distilled water for analysis)

The 6-mark water treatment question is one of the most reliably assessed extended writing questions in Combined Science Chemistry.

The Topic Mastery Sheet covers the three-stage process with particle-level explanations for each, the limitation of filtration (does not remove soluble substances), the exact required wording for the chlorination answer (and the three rejected alternatives), the full LoR indicative content for the 6-mark question, and the 2-mark explanation for using distilled water in analysis. Seawater treatment by distillation and aquifer extraction are also covered.

The Student Exam Practice Sheet (20 marks) covers: sedimentation description, why water isn’t pure after filtration, chlorination reason, distilled water explanation, seawater distillation, safety, potable water definition, aquifer knowledge, technique selection, and the full 6-mark LoR water treatment question with Level descriptor rubric.

The Teacher Answer Key gives the complete Level 3 indicative content and highlights the three common chlorination answers that are rejected by Edexcel.

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