Exercise 1 — IGCSE 0654 Oct/Nov 2024 Paper 21 Q25
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Correct answer: D
Cambridge IGCSE·Co-ordinated Sciences 0654·Chemistry
Water
Key knowledge — Chemistry Of The Environment
Key facts & rules
- Clean dry air: ~78% N₂, ~21% O₂, ~0.04% CO₂, ~1% Ar and other noble gases.
- Acid rain: caused by SO₂ (burning fossil fuels) and NOₓ (car engines) dissolving in rainwater.
- Greenhouse effect: CO₂, CH₄, H₂O absorb infrared radiation re-emitted from Earth → warming.
- Water treatment: screening → sedimentation → filtration → chlorination.
- Hard water: contains Ca²⁺ or Mg²⁺ ions; forms scum with soap; removed by ion exchange or boiling (temporary hardness).
- Ozone layer (O₃): in stratosphere; absorbs harmful UV radiation; damaged by CFCs.
IGCSE Chemistry — Water
3 Cambridge IGCSE 0654 questions on water, across all three components.
About water on IGCSE 0654
Every Cambridge IGCSE Co-ordinated Sciences 0654 question on water (Chemistry of the environment, Chemistry), across all three exam components. Theory and alternative-to-practical come with full mark schemes; multiple choice is interactive — click an option to check it.
Multiple choice
Water — Extended multiple choice questions2 total · Paper 2
Exercise 2 — IGCSE 0654 May/June 2024 Paper 23 Q24
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Correct answer: B
Alternative to practical
Exercise 1 — IGCSE 0654 May/June 2023 Paper 63 Q3
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