Chemistry and the environment
| English | Chinese | Pinyin |
|---|---|---|
| combustion | 燃烧 | rán shāo |
| greenhouse effect | 温室效应 | wēn shì xiào yìng |
| acid rain | 酸雨 | suān yǔ |
| pollution | 污染 | wū rǎn |
Burning carbon is where the two subjects meet
- Combustion 燃烧 of a fuel combines carbon and hydrogen with oxygen, releasing energy, carbon dioxide and water.
- The carbon in the fuel was removed from the air millions of years ago; burning returns it in a few seconds.
- That single sentence is the whole mechanism behind the greenhouse effect 温室效应 as a chemistry problem.
Where was the carbon in a fossil fuel before it was burned?
Burning returns in seconds what took millions of years to remove, which is the whole mechanism.
The greenhouse effect
- Sunlight passes through the atmosphere and warms the surface. The warm surface radiates infrared.
- Greenhouse gases absorb that infrared and re-emit it in all directions, including back down, so the surface is warmer than it would otherwise be.
- The effect itself is not the problem — without it the planet would be far colder. The problem is a change in its size.
What is the problem with the greenhouse effect?
The effect keeps the planet habitable. The concern is the change, not the mechanism.
Acid rain, and the shape of the answer
- Acid rain 酸雨 forms when sulfur and nitrogen oxides from combustion dissolve in water vapour.
- Pollution 污染 questions have a repeating shape: a substance, a source, a mechanism, an effect, and a mitigation.
- ⚠ Answers that name the substance and jump to the effect skip the two steps carrying the marks.
Put the five parts of a pollution answer in order.
Answers that name the substance and jump to the effect skip the two steps carrying the marks.
One pollutant, all five steps.
Substance: sulfur dioxide. Source: burning coal containing sulfur.
Mechanism: it dissolves in water vapour to form sulfurous and sulfuric acid.
Effect: rain acidifies lakes and soils, damaging fish populations and leaching nutrients.
Mitigation: remove sulfur from the fuel, or scrub it from the flue gases.
Five sentences, five marks. The structure works for any pollutant in the module, including one you have never seen.
Write the mechanism step for nitrogen oxides forming acid rain.
Example: "Nitrogen oxides dissolve in water vapour in the atmosphere to form nitric acid, which then falls as rain."
Chemistry supplies the mechanism; policy chooses the response. Questions expect you to keep them apart — "what happens" and "what should be done" are different claims, and mixing them costs marks in both directions.
Do not confuse the greenhouse effect with the hole in the ozone layer. They are different gases, different mechanisms and different parts of the atmosphere, and the confusion is common enough that examiners test it directly.
The greenhouse effect and the hole in the ozone layer are the same phenomenon.
Different gases, different mechanisms, different parts of the atmosphere — and examiners test the confusion directly.