Quick Simpler Start
You learn about the air around us, how pollution happens, and how chemistry explains climate and ozone issues.
When you revise this chapter, ask yourself: "Can I explain this to a friend in one easy paragraph?" If yes, you are in a good place.
Interactive Simulator
This small tool gives you a quick visual check before you move deeper into the chapter notes.
Atmosphere Explorer
Pick a gas and the tool gives a quick explanation of its role or risk.
PREMIUM REVISION NOTES
ILC Higher Chemistry — Option 1B: Atmospheric Chemistry
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1. Learning Objectives
- Describe oxygen, nitrogen and carbon dioxide in the atmosphere and their chemistry.
- Explain nitrogen fixation and the nitrogen cycle.
- Distinguish carbon monoxide from carbon dioxide and explain their formation.
- Describe atmospheric pollution, acid rain and gas-scrubbing methods.
- Explain ozone formation and ozone depletion by CFCs and HCFCs.
- Discuss greenhouse gases, global warming and pollution-control measures.
2. Oxygen and Nitrogen
| Gas | Main facts |
|---|---|
| Oxygen | About 21% of dry air; supports combustion and respiration; made industrially by liquefaction and fractional distillation of air. |
| Nitrogen | About 78% of dry air; relatively inert because of the strong N≡N bond; used in ammonia manufacture. |
3. Nitrogen Fixation and the Nitrogen Cycle
Nitrogen fixation converts atmospheric nitrogen into usable nitrogen compounds.
| Type | Example |
|---|---|
| Industrial | Haber Process |
| Biological | Bacteria in soil or root nodules |
| Atmospheric | Lightning forming nitrogen oxides |
The cycle includes fixation, nitrification, plant uptake, feeding, decay and denitrification.
4. Carbon Dioxide and Carbon Monoxide
Carbon dioxide
Formed in complete combustion, respiration and fermentation. It is an acidic oxide and a greenhouse gas.
Carbon monoxide
Formed in incomplete combustion. It is highly poisonous because it binds strongly to haemoglobin.
5. Carbon Cycle and Greenhouse Effect
The carbon cycle moves carbon between atmosphere, oceans, living things and fossil fuels.
Greenhouse gases absorb outgoing infrared radiation and warm the atmosphere.
| Important greenhouse gases | Examples |
|---|---|
| Natural and enhanced | CO2, H2O vapour, CH4, N2O, CFCs |
6. Atmospheric Pollution and Acid Rain
| Pollutant | Source | Main effect |
|---|---|---|
| SO2 | Burning sulfur-containing fuels | Acid rain, irritation |
| NOx | Engines and high-temperature combustion | Acid rain, smog |
| CO | Incomplete combustion | Toxic poisoning |
| Particulates | Smoke and diesel exhaust | Respiratory problems |
Acid rain forms when SO2 and NOx dissolve in atmospheric moisture.
Waste gases may be scrubbed with limestone or lime.
7. Ozone Layer and CFCs
The ozone layer absorbs harmful ultraviolet radiation.
CFCs release chlorine radicals under UV light, which destroy ozone catalytically.
HCFCs are less damaging than CFCs but still not ideal.
8. Pollution Control
- Use cleaner fuels and lower-sulfur fuels.
- Use catalytic converters.
- Scrub waste gases.
- Reduce fossil-fuel use and improve efficiency.
- Phase out ozone-depleting substances.
9. Revision Sheet
- Know nitrogen fixation and the nitrogen cycle.
- Know the difference between CO and CO2.
- Know SO2, NOx and acid rain.
- Know ozone formation and CFC ozone depletion.
- Know greenhouse gases and pollution-control methods.