🌍 Environment Masterclass: Past Paper Exam
Fertilisers · Eutrophication · Water Treatment · Synoptic Analysis
15
Questions
48
Total Marks
3
Sections
The Eutrophication Pipeline
Visual overview — trace the journey from farm fertiliser to lake catastrophe to water treatment
The Farm to River Pipeline
15 marksNPK fertilisers are highly soluble. Explain why this solubility is beneficial for the plant, but poses a risk to nearby rivers.
State TWO nutrients in NPK fertilisers and name ONE compound that could supply EACH of them.
Ammonia is reacted with nitric acid to produce ammonium nitrate fertiliser. Write a balanced symbol equation for this reaction, including state symbols.
Calculate the percentage by mass of nitrogen in ammonium nitrate, NH₄NO₃. Give your answer to 3 significant figures. [Ar: N=14, H=1, O=16]
A farmer applies fertiliser before a heavy rainstorm. Explain why this application is poor agricultural practice.
The Ecological Impact
15 marksDescribe the sequence of events (eutrophication) that occurs when excessive nitrate ions enter a lake. Your answer should be in the correct chronological order.
Explain why eutrophication causes a decrease in BIODIVERSITY, not just a decrease in fish numbers.
Distinguish between a 'point source' and a 'diffuse source' of water pollution. Give ONE example of each.
Suggest THREE ways farmers could reduce the risk of fertiliser leaching into rivers without stopping fertiliser use.
The pH of a eutrophic lake is often higher during the day and lower at night. Explain this observation.
Making It Safe
18 marksRiver water contaminated with algae and bacteria is extracted for drinking. State the TWO essential treatment stages required and the purpose of EACH.
Explain why SEDIMENTATION is used as a step BEFORE filtration in large-scale water treatment plants.
Evaluate the use of chlorine to treat drinking water. Include both benefits and risks in your answer.
A water treatment plant adds chlorine at a concentration of 0.5 mg per litre of water. Calculate the mass of chlorine required to treat 2,000,000 litres of water. Give your answer in kg.
Extended Writing: 'Human agricultural activity is the primary cause of water pollution.' Using your knowledge of fertilisers, eutrophication, and water treatment, assess the extent to which you agree with this statement. [6 marks — Quality of Extended Response assessed]
📊 Key Examiner Vocabulary — Must Use These Words
leaching
ions washed through soil by rain
eutrophication
excess nutrients → ecological disruption
algal bloom
rapid multiplication of algae
deoxygenation
removal of dissolved O₂ from water
aerobic bacteria
O₂-consuming decomposers
filtration
removal of solid particles
chlorination
adding Cl₂ to kill bacteria
biodiversity
variety of species in an ecosystem
Limitless IGCSE Chemistry · Environment Exam · Cambridge 0620 (2026-2028) · Topic 10.3
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