Environmental and Atmospheric Chemistry
This topic is really six chemistry problems wearing one trench coat: clean water, a stable atmosphere, burning fuel, trapping heat, acidifying rain, and a hole in the ozone layer — and every single one traces back to the same handful of gases (N, O, CO, SO, NOx, CFCs) doing different things in different places. Examiners love data tables here — altitude vs. gas %, bond energies, electron configurations — so the real skill isn't memorising facts, it's reading a table and explaining the pattern, not just describing it.
Overview — how the chapter fits together
Everything in this topic sits on one baseline: the composition of the atmosphere is remarkably constant, not because its gases refuse to react, but because production and removal processes are balanced — a steady state. Human activity (combustion, refrigerants, industry) tips that balance in specific, traceable ways: burning fuel adds CO/SO/NOx, CFCs release Cl radicals in the stratosphere, and untreated water/waste disrupts local ecosystems. Sustainability is the thread that runs back through all of it — reduce the demand, and you reduce every downstream problem.
- Water treatment and recycling are about human systems intervening to manage resources responsibly.
- Atmospheric composition, combustion and greenhouse gases are about what's actually in the air and where it came from.
- Acid rain and ozone depletion are the two classic 'unintended consequence' stories — both driven by gases that seemed harmless where they were released.
The shape of the chapter
Command terms you'll actually meet in this topic
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| Identify | Give a name/term/value straight from data or memory — no reasoning | Criterion A | 1 mark for the correct word/value only; adding explanation you weren't asked for doesn't earn extra marks |
| State | Give a brief, precise fact or definition | Criterion A | Full credit for a concise correct statement — a long paragraph wastes time, not marks |
| Describe | Give a detailed, ordered account with relevant detail, no reasoning required | Criterion A | Marks awarded per correct relevant point given, often in the order they occur |
| Explain | State what happens AND why it happens — mechanism, not just outcome | Criterion A/D | Giving only the 'what' typically earns half the marks; the 'why' is the second mark |
| Deduce | Reach a conclusion using the data given, not general background knowledge | Criterion B | Marks require you to reference specific figures/trends from the source given |
| Analyse | Break down data to identify patterns, relationships, or components | Criterion B | Must quote actual numbers/trends from the table — describing the topic generally scores nothing |
| Evaluate | Weigh strengths and limitations and reach a justified judgement | Criterion D | A concluding judgement sentence is required for top marks — a list of pros/cons alone is capped |
Key point
Overview