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P4 General Studies: Air, Combustion and Rusting (Paper 4 (error clinic))
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 4 (error clinic))
Paper four revisits the mistakes from the first three papers, fixing ideas and numbers together.
Direct answers Ask first what is burning or rusting, then decide whether to use composition, share or 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, 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 three things must all be present for burning?
- FoundationIs rusting a physical change or a chemical change?
- FoundationWhy do aluminium window frames not keep rusting away outdoors like iron?
- IntermediateBurning uses 105 mL of oxygen from 500 mL of air. What is left, and what share was oxygen?
- IntermediateTwelve of fifteen nails in damp conditions rust. What share is that?
- IntermediateHow can iron be kept from rusting?
- ChallengeSix of eight sealed jars show the water rising about a fifth. What share is that?
- ChallengeA 50 g nail weighs 60 g after rusting. How much mass is gained, and what share of the original is that?
- ChallengeIn 500 mL of air, nitrogen is about 78 per cent and oxygen about 21 per cent. How much more nitrogen is there?
- Error redoError clinic: a candle in a sealed jar goes out because all the air has vanished. Is that right?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | A fuel, oxygen and a high enough temperature. | Missing any one of the three and nothing burns; putting out a fire means removing one of them. |
| 2 | A chemical change. | Rusting forms a new substance, rust, which cannot easily be turned back into the original iron. |
| 3 | A tight oxide layer forms on the surface and protects the metal beneath. | That oxide film keeps oxygen and water away from the aluminium, so corrosion is very slow. |
| 4 | 395 mL left; oxygen was 21.0 percentage points. | Five hundred minus 105 leaves 395 mL; 105 over 500 times 100 is 21.0 percentage points. |
| 5 | 80.0 percentage points. | Twelve divided by fifteen and multiplied by 100 gives 80.0 percentage points. |
| 6 | Paint it, oil it, plate it or keep it dry, so the iron is shielded from oxygen or water. | Every method follows one idea: cut off either the oxygen or the water. |
| 7 | 75.0 percentage points. | Six divided by eight and multiplied by 100 gives 75.0 percentage points. |
| 8 | 10 g gained, which is 20.0 percentage points. | Sixty minus 50 gives 10 g; 10 over 50 times 100 is 20.0 percentage points, and the gain is the oxygen joined to the iron. |
| 9 | 285.0 mL more. | Nitrogen is 500 times 0.78, which is 390.0 mL; oxygen is 105.0 mL; the difference is 285.0 mL. |
| 10 | No. | Only the oxygen is used up; plenty of nitrogen remains, but not enough oxygen to keep burning. |
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 the three parts of a closed circuit plus three safety habits.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.