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P4 General Studies: Air, Combustion and Rusting (Paper 1 (basics))
Tutor Prep Guide · the make-up of air and oxygen, burning needing oxygen and how fires are put out, the two conditions for rusting, rust prevention and the mass gained by rust
P4 General Studies: Air, Combustion and Rusting (Paper 1 (basics))
Paper one covers the make-up of air, burning needing oxygen, and rusting needing oxygen and water.
Direct answers Ask first which gas is involved, then how much, and only then work out the share.
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, Combustion and Rusting |
| Level | parts of a closed circuit, conductors against insulators, series against parallel, adding up battery voltage, and electrical safety |
02 Questions (10 items)
- FoundationWhich gas is most abundant in air?
- FoundationWhich gas in the air does burning need?
- FoundationWhich two conditions must both be present for an iron nail to rust?
- IntermediateOxygen is about 21 per cent of air. How much oxygen is there in 100 mL of air?
- IntermediateAir is about 78 per cent nitrogen and 21 per cent oxygen. What share do the remaining gases take?
- IntermediateWhy does a candle go out when a glass is placed over it?
- ChallengeA sealed bottle holds 200 mL of air with about 21 per cent oxygen. If burning uses all the oxygen, how many mL of gas are lost?
- ChallengeNine of twelve objects are made of iron. What share is that?
- ChallengeFive hundred mL of air contains 105 mL of oxygen. What share is oxygen?
- Error redoError clinic: iron rusts only because it touches water. Is that right?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Nitrogen, about 78 per cent of the air. | Air is mostly nitrogen; oxygen takes about 21 per cent and the rest is a small share. |
| 2 | Oxygen. | Without oxygen a fuel cannot keep burning, which is why fire fighting often cuts off the oxygen. |
| 3 | Oxygen and water. | Water alone or oxygen alone seldom rusts iron; rust forms when both are present. |
| 4 | 21.0 mL. | One hundred multiplied by 21 and divided by 100 gives 21.0 mL. |
| 5 | 1 percentage points. | One hundred minus 78 and minus 21 leaves 1 percentage points. |
| 6 | The oxygen inside the glass is used up. | The glass keeps fresh air out, so once the oxygen inside is gone the burning stops. |
| 7 | 42.0 mL. | Two hundred multiplied by 21 and divided by 100 gives 42.0 mL. |
| 8 | 75.0 percentage points. | Nine divided by twelve, then multiplied by 100, gives 75.0 percentage points. |
| 9 | 21 percentage points. | One hundred five divided by 500 and multiplied by 100 gives 21, matching the usual share of oxygen. |
| 10 | No. | Rusting needs oxygen and water together; with no oxygen at all, water alone does not rust iron. |
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.
After paper one, take paper two and sort out series against parallel in one pass.Tutor Registration →
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