This exam focus covers Exam Focus within Water Treatment for GCSE Chemistry. Revise Water Treatment in Using Resources for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 11 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 11 of 13
Practice
20 questions
Recall
15 flashcards
🎯 Exam Focus
High Frequency
Water treatment is one of the most frequently examined topics in Using Resources. Expect at least one question on the stages of treatment in every exam series.
Common Question Types:
- Order the stages [2 marks]: "Place the following stages of water treatment in the correct order." — Must know: Screening → Sedimentation → Filtration → Chlorination.
- Explain a stage [2 marks]: "Explain the purpose of chlorination in water treatment." — Kills microorganisms/bacteria/pathogens; acts as a disinfectant.
- Define potable water [1 mark]: "What is meant by potable water?" — Safe to drink; not the same as pure water.
- Compare methods [3-4 marks]: "Compare distillation and reverse osmosis as methods of desalination." — Must compare energy use, cost, and effectiveness.
Key Points Examiners Look For:
- Potable water ≠ pure water (a very common mark-winning distinction)
- Chlorination kills pathogens — not just "cleans" the water
- Sedimentation uses gravity; filtration uses physical barriers
- Desalination is expensive because it is energy-intensive
Quick Check: What is the difference between potable water and pure water?
Potable water is safe to drink but may contain dissolved minerals and small amounts of chlorine — it is NOT chemically pure. Pure water contains only H₂O molecules with nothing else dissolved. Potable water meets health safety standards; it does not need to be chemically pure.
Quick Check: State the four main stages of drinking water treatment in the correct order.
1. Screening — metal grids remove large debris (leaves, twigs). 2. Sedimentation — water sits in tanks; heavy particles settle by gravity. 3. Filtration — water passes through sand and gravel to remove finer particles. 4. Chlorination — chlorine added to kill bacteria and other pathogens.
Quick Check: Explain why desalination is not widely used in the UK to produce drinking water.
Desalination is very energy-intensive and therefore expensive. The UK has sufficient rainfall and freshwater sources (rivers and reservoirs) that can be treated using the much cheaper standard water treatment process. Desalination is mainly used in water-scarce regions such as the Middle East where freshwater sources are limited.