A complete revision and exam practice pack for SC2e Drinking Water, covering the full Pearson Edexcel GCSE Chemistry (9–1) Separate Science specification for this topic (C2.8, C2.12).

Topic Mastery Sheet (PDF) - a comprehensive student reference that opens with the important distinction between potable (safe to drink) and pure (chemistry definition): tap water is a mixture containing dissolved minerals and chlorine - it is potable but not pure. The three-stage treatment process for river and reservoir water is explained with genuine understanding of what each stage does and why it is necessary. Sedimentation allows large insoluble particles to settle under gravity, sometimes aided by alum which causes fine particles to clump together. Sand and gravel filtration then removes smaller suspended particles that did not settle. Chlorination kills bacteria and other microorganisms - but importantly, neither filtration nor chlorination removes dissolved salts, which is why treated tap water still contains minerals. A clear table shows what each stage removes and what it leaves behind. The sea water section explains the simple distillation process for desalination and discusses why large-scale distillation is expensive (enormous energy requirement to boil water at scale) and why fractional distillation is not appropriate (water is the only liquid in sea water). The water purity for analysis section explains the problem with using tap water in chemical tests: dissolved ions such as chloride will trigger false positive results, so distilled or deionised water must be used to get reliable results. The stretch section covers reverse osmosis, water fluoridation, and the chemistry of water hardness.

Student Exam Practice Sheet (PDF + DOCX) - seven exam-style questions covering reasons for chlorination, what sedimentation removes, why water is not pure after filtration, disadvantages of large-scale distillation, why fractional distillation is not used for sea water, water purity for analysis, and a six-mark extended writing question on the full water treatment process.

Teacher Answer Key (PDF + DOCX) - full tick-point mark scheme including Level of Response descriptors and indicative content for the six-mark question.

©BoxsiderResources. Licensed for classroom use by the purchasing teacher. Not for redistribution or resale.