📋 Structured Questions
These questions test key concepts from Topic 10. Attempt each question on paper, then click "Show Mark Scheme" to check your answer.
Question 1: Sacrificial Protection
2 marksMagnesium blocks are fixed to the hull of steel ships to prevent them from rusting.
(a) Explain how the magnesium blocks prevent the steel from rusting. [2]
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- Magnesium is more reactive (than iron/steel) [1]
- Magnesium corrodes / oxidises instead of the iron / provides sacrificial protection [1]
Question 2: The Haber Process
3 marksAmmonia is produced in the Haber process: N₂ + 3H₂ ⇌ 2NH₃
(a) Name the sources of nitrogen and hydrogen used in the Haber process. [2]
(b) How is ammonia separated from the unreacted gases? [1]
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- (a) Nitrogen: from the air / atmosphere [1]
- Hydrogen: from natural gas / methane [1]
- (b) The mixture is cooled (so that ammonia liquefies / condenses while H₂ and N₂ remain as gases) [1]
Question 3: Sustainable Recycling
4 marksCopper can be obtained by recycling scrap copper wire.
(a) Describe how scrap copper wire can be recycled to make new copper water pipes. [2]
(b) Suggest two reasons why recycling scrap copper is more sustainable than extracting copper from copper ores. [2]
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- (a) Copper is heated until it melts [1]
- Recast / reformed / reshaped into pipes [1]
- (b) Any two: Uses less energy [1]
- Conserves copper ore / Less waste / Less landfill / Less habitat destruction from mining [1]
Question 4: Producing Potable Water
4 marksIn the UK, potable (drinking) water is produced from different sources of fresh water.
(a) Explain how potable water is produced from fresh water. [4]
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- Choose an appropriate source of fresh water (rivers, lakes, boreholes) [1]
- Pass the water through filter beds [1]
- To remove undissolved solids [1]
- Sterilise the water using chlorine / ozone / UV light to destroy harmful microbes [1]
Question 5: Waste Water Treatment
4 marksSewage is waste water. Sewage contains organic matter.
(a) Describe how sewage is treated to remove organic matter. [4]
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- Screening / grit removal to remove large solids [1]
- Sedimentation to produce sewage sludge and effluent [1]
- Anaerobic digestion of (solid) sewage sludge [1]
- Aerobic biological treatment of (liquid) effluent [1]
Question 6: Phytomining
4 marksCopper is extracted from low-grade ores by phytomining.
(a) Describe how copper is extracted from low-grade ores by phytomining. [4]
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- Grow plants on land containing copper ores [1]
- Plants are burnt to produce ash [1]
- Ash is dissolved in acid to produce a solution of a copper compound [1]
- Electrolysis of the solution OR displacement using scrap iron [1]
Question 7: Potable Water & Desalination ⭐ Extended Response
6 marksIn many parts of the world, drinking water is produced by desalination of sea water. In the UK, potable water is predominantly produced from fresh water sources such as groundwater.
(a) Describe how potable water is produced from fresh water, and explain why desalination is not commonly used in areas with adequate supplies of fresh water. [6]
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Level 3 (5–6 marks): Clear, logically sequenced description of fresh water treatment, along with justified evaluation comparing the energy and cost requirements of desalination.
Level 2 (3–4 marks): Describes some steps of water treatment or explains the issue with desalination, but lacks detail in one area.
Level 1 (1–2 marks): Relevant but isolated points, such as naming a sterilising agent or stating desalination is expensive.
Indicative content:
- Fresh water is passed through filter beds (sand/gravel) to remove solid particles/undissolved solids
- Water is then sterilised to kill harmful microbes using chlorine, ozone, or UV light
- Desalination removes salt via distillation or reverse osmosis
- Desalination requires large amounts of energy, making it much more expensive
- Therefore it is only used where fresh water is scarce
Question 8: Required Practical — Distillation of Water 🔬
4 marksA student is provided with a sample of salty water and is asked to obtain a sample of pure water from it.
(a) Describe the process of distillation that the student should use to produce pure water from the salty water sample. [4]
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- Heat the salty water until it reaches its boiling point [1]
- The water evaporates / turns into water vapour [1]
- The vapour passes into a condenser where it cools down [1]
- The vapour condenses to form pure liquid water, leaving the salt behind in the flask [1]
Question 9: Required Practical — Analysing & Purifying Water ⭐🔬 Extended Response
6 marksA student collected a sample of impure river water. They know that potable water is safe to drink but is not chemically pure because it contains dissolved substances.
(a) Describe how the student could first analyse the water sample to test its purity, and then outline the full method they would use to safely produce a chemically pure sample of water from the river water. [6]
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Level 3 (5–6 marks): Detailed, logical method including how to test the water sample (pH and/or dissolved solids) and a comprehensive description of the distillation process, correctly linking changes of state to equipment.
Level 2 (3–4 marks): Mentions either purity tests or distillation in good detail, or provides a basic outline of both. Some terminology may be missing.
Level 1 (1–2 marks): Simple statements about heating water or testing it. Logical sequence incomplete, key terms may be omitted.
Indicative content:
- Testing for purity: test pH using a pH meter or universal indicator — potable water: pH 6.5–8.5; pure water: pH 7
- Test for dissolved solids: evaporate a small sample on a watch glass — if pure, no residue left behind
- Purification by distillation: pour impure water into a flask connected to a condenser
- Heat until water reaches boiling point → water evaporates (separating from impurities)
- Vapour travels into the condenser → condenses back into liquid pure water
- Impurities (salt, bacteria) are left behind in the flask