Revise: Chemistry and Green Environment
Earth's atmosphere, hydrosphere and lithosphere, air/water/soil pollutants, the greenhouse effect, radioactive substances in the environment, and how chemistry supports sustainable development.
CO blocks oxygen transport; SO₂/NOₓ cause acid rain; NOₓ + sunlight → smog.
Vehicle exhaust NOₓ reacts in sunlight to form ground-level ozone.
Fertiliser runoff causes eutrophication — oxygen depletion, not direct poisoning.
Algal blooms die and decompose, suffocating fish.
Greenhouse gases trap infrared radiation the Earth re-emits.
CO₂ has risen from ~280 ppm to over 420 ppm since industrialisation.
Chemistry drives environmental SOLUTIONS too — not just problems.
Catalytic converters reduce harmful vehicle emissions.
Earth's three spheres constantly exchange chemicals — pollution spreads between them.
Acid rain moves SO₂ pollution from atmosphere to hydrosphere and lithosphere.
Each pollutant has its own distinct chemical mechanism of harm.
CO binds haemoglobin more strongly than oxygen does.
Heavy metals/pesticides are directly toxic and can bioaccumulate up the food chain.
Fertiliser runoff → algal bloom → decomposition → oxygen depletion.
The natural greenhouse effect is essential; the problem is its human-caused enhancement.
Sunlight passes through; re-radiated infrared gets trapped by CO₂.
Radioactivity occurs naturally AND from human sources; half-life determines hazard duration.
Caesium-137 (decades half-life) persists far longer than iodine-131 (days).
Green chemistry prevents pollution at the source, not just cleans it up after.
Biodegradable plastics break down via designed polymer chemistry.