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Chemistry of the Environment | IGCSE Chemistry (0620)

Chemistry of the Environment | IGCSE Chemistry (0620) | SM-Educate
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CS-991 · Module I-10

10 · Chemistry of the Environment

Cambridge IGCSE Chemistry 0620 · Core + Supplement · 2026–2028
Quick Revision
🌬️ Air & Pollutants💧 Water Treatment↻ Nitrogen Cycle

10.1 Composition of Air and Pollutants

GasApproximate %
Nitrogen78%
Oxygen21%
Argon (and other noble gases)~1%
Carbon dioxide~0.04%

Common pollutants: Carbon monoxide (from incomplete combustion, binds to haemoglobin instead of oxygen); Sulfur dioxide and nitrogen oxides (cause acid rain); Carbon dioxide (greenhouse gas, contributes to global warming).

🎥 Video lectures for this sub-topic — coming soon
Q1: The most abundant gas in clean, dry air is:
a) Oxygen b) Carbon dioxide c) Nitrogen d) Argon
Show Answer
✅ c) Nitrogen (about 78%)
Q2: Acid rain is mainly caused by:
a) Carbon dioxide b) Sulfur dioxide and nitrogen oxides c) Oxygen d) Argon
Show Answer
✅ b) Sulfur dioxide and nitrogen oxides

10.2 Water Treatment and the Nitrogen Cycle

Water treatment typically involves: sedimentation (larger particles settle), filtration (removes remaining solid particles), and chlorination (kills harmful microorganisms).

Nitrogen cycle: Nitrogen gas (N₂) is very unreactive. Nitrogen-fixing bacteria in soil convert it into nitrates, usable by plants. Plants use nitrates to build proteins; animals get nitrogen by eating plants; decomposition and denitrifying bacteria return nitrogen to the atmosphere.

🎥 Video lectures for this sub-topic — coming soon
Q1: Chlorination in water treatment is used to:
a) Remove solid particles b) Kill harmful microorganisms c) Reduce pH d) Add nitrogen
Show Answer
✅ b) Kill harmful microorganisms
Q2: Nitrogen-fixing bacteria convert atmospheric nitrogen into:
a) Oxygen b) Carbon dioxide c) Nitrates (usable by plants) d) Water
Show Answer
✅ c) Nitrates (usable by plants)
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