中文（繁體）
中文（简体）
English
P4 General Studies: Air, Burning and Rusting (Paper 3: challenge)
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 3: challenge)
The third paper practises reasoning and multi-step work: use volumes, times and masses to explain what happens.
Direct answers In a multi-step question write the number for each step before adding units, and the answer stays reliable.
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)
- FoundationA candle burns under a jar and water rises about one fifth of the way. What share of air is oxygen?
- FoundationA room holds 50 cubic metres of air and oxygen is about 21 per cent. What volume of oxygen is that?
- FoundationWhat do rusting and burning have in common?
- IntermediateInhaled air is 21 per cent oxygen and exhaled air about 16 per cent. How much oxygen is used from 100 litres?
- IntermediateA 250 millilitre cup holds about 52.5 millilitres of oxygen and the candle uses 10 millilitres a minute. How long can it burn?
- IntermediateA nail grows from 5.6 grams to 8.0 grams as it rusts. What is the extra 2.4 grams?
- ChallengeWhy does galvanising protect iron?
- ChallengeTube A holds dry air, tube B salt water, tube C boiled distilled water sealed with oil. After a week how many rust?
- Challenge12 grams of carbon burn in 32 grams of oxygen. What mass of carbon dioxide forms?
- Error redoA pupil says matter disappears when it burns. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | About 20 per cent, one fifth | The oxygen is used up and water fills its volume, so the water rises about one fifth. |
| 2 | 10.5 cubic metres | 50 times 21 per cent gives 10.5 cubic metres. |
| 3 | Both need oxygen and both are oxidation | Burning is fast and rusting is slow, but both are combinations with oxygen. |
| 4 | 5 litres | 21 per cent minus 16 per cent is 5 per cent, and 5 per cent of 100 litres is 5 litres. |
| 5 | About 5.25 minutes | 52.5 divided by 10 gives 5.25 minutes. |
| 6 | Oxygen from the air that has combined with the iron | The extra mass is oxygen that has joined the iron, not more iron appearing. |
| 7 | Zinc is more reactive than iron, so it is oxidised first and protects the iron | The zinc corrodes first and the iron is protected, which is called sacrificial protection. |
| 8 | Only B rusts | A lacks water and C lacks oxygen, so only B has both water and oxygen. |
| 9 | 44 grams | 12 plus 32 is 44 grams, which is conservation of mass. |
| 10 | It turns into gases that spread into the air, and the mass is still there | Mass is conserved; the solid simply becomes invisible gases. |
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.
Paper four revisits the ideas that are most often mixed up.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.