中文（繁體）
中文（简体）
English
P4 General Studies: Air, Burning and Rusting (Paper 4: mistake clinic)
Tutor Prep Guide · composition of air, conditions for burning, conditions for rusting and ways to prevent rust
P4 General Studies: Air, Burning and Rusting (Paper 4: mistake clinic)
The fourth paper redoes the points most often missed: rusting needs water, rusting is a chemical change, and mass is conserved.
Direct answers Read each question aloud and check whether it asks about the conditions for rusting or about mass.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: P4 General Studies: Air, Burning and Rusting |
| Level | composition of air, conditions for burning, conditions for rusting and ways to prevent rust |
02 Questions (10 items)
- FoundationWhich gas is the second most abundant in air?
- FoundationWhy does carbon dioxide from a fire extinguisher put out a fire?
- FoundationWhat must iron have at the same time in order to rust?
- IntermediateHow much oxygen is in 200 cubic centimetres of air?
- IntermediateDoes a nail rust in a dry sealed jar for a week?
- IntermediateIs rusting a physical change or a chemical change?
- ChallengeHow much nitrogen is in 1 000 millilitres of air?
- ChallengeWrite down two ways of preventing rust.
- ChallengeWhere does the extra mass of rusted iron come from?
- Error redoA pupil says rusting has nothing to do with burning. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Oxygen, about 21 per cent | Nitrogen at about 78 per cent comes first and oxygen at about 21 per cent second. |
| 2 | It does not support burning and is heavier than air, so it blankets the fire | It keeps oxygen away and the fire cannot carry on. |
| 3 | Oxygen and water | Take away either one and no rust forms, which is exactly how rust prevention works. |
| 4 | 42 cubic centimetres | 200 times 21 per cent gives 42 cubic centimetres. |
| 5 | No, because there is no water | The drying agent takes the water vapour away, so only one condition is left. |
| 6 | A chemical change | A new substance, rust, is formed, so it is a chemical change. |
| 7 | 780 millilitres | 1 000 times 78 per cent gives 780 millilitres. |
| 8 | Painting and oiling (or keeping it dry, or galvanising) | Anything that shuts out oxygen or water will prevent rust. |
| 9 | From oxygen in the air | The oxygen combines with the iron and stays in the rust, so the mass rises. |
| 10 | Both need oxygen and both are oxidation | One is fast and one is slow, but they are the same kind of reaction. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
With all four done, go back to the chapter page and revise air and rust prevention.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.