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S5 Physics Gas Laws, Paper 2: Charles law and the combined gas law
S5 Physics Gas Laws, Paper 2: Charles law and the combined gas law
At constant pressure the volume is proportional to absolute temperature, and temperatures must be converted to kelvin first.
Focus Add 273 to reach kelvin, then use V1/T1 = V2/T2 or the combined law.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 3 · Intermediate 4 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Physics: Gas Laws |
| Level | S4 to S5 |
02 Questions (10 items)
- Foundation2.0 L of gas at 300 K is heated to 600 K at constant pressure. Find the volume.
- FoundationConvert 27 degrees Celsius to absolute temperature.
- Foundation3.0 L of gas at 80 kPa is compressed to 1.5 L at constant temperature. Find the pressure.
- Intermediate1.0 L of gas at 273 K is heated to 546 K at constant pressure. Find the volume.
- IntermediateA gas in a fixed 400 cm3 container is at 90 kPa and 200 K. It is heated to 300 K. Find the pressure.
- Intermediate2.0 L of gas at 100 kPa and 300 K changes to 200 kPa and 400 K. Find the volume to 3 significant figures.
- IntermediateA gas at 4.0 L has a pressure of 50 kPa. It expands to 8.0 L at constant temperature. Find the pressure.
- Challenge3.0 L of gas at 250 K is cooled to 200 K at constant pressure. Find the volume.
- Challenge2.0 L of gas at 27 C is heated to 127 C at constant pressure. Find the volume to 3 significant figures.
- Error redoCorrect the claim: a gas heated from 27 C to 54 C at constant pressure doubles its volume.
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 4.0 L | At constant pressure V is proportional to T, so doubling the temperature doubles the volume. |
| 2 | 300 K | Add 273 to the Celsius value: 27 + 273 = 300 K. |
| 3 | 160 kPa | Halving the volume doubles the pressure to 160 kPa. |
| 4 | 2.0 L | The absolute temperature doubles from 273 K to 546 K, so the volume doubles. |
| 5 | 135 kPa | At fixed volume P is proportional to T: 90*300/200 = 135 kPa. |
| 6 | 1.33 L | Combined law: 2.0*(100/200)*(400/300) = 1.33 L. |
| 7 | 25 kPa | PV stays at 200, so 200/8.0 = 25 kPa. |
| 8 | 2.4 L | V is proportional to T: 3.0*200/250 = 2.4 L. |
| 9 | 2.67 L | Convert to kelvin first: 300 K rises to 400 K, then 2.0*400/300 = 2.67 L. |
| 10 | It should read: 27 C is 300 K and 54 C is 327 K, so the volume only rises to 1.09 times. | Compare kelvin values: 327/300 = 1.09, so the volume rises by only about 9 percent. |
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.
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