Question 22N.2.SL.TZ0.2b.ii
| Date | November 2022 | Marks available | [Maximum mark: 2] | Reference code | 22N.2.SL.TZ0.2b.ii |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | b.ii | Adapted from | N/A |
The water is heated. Explain why the quantity of air in the storage tank decreases.
[2]
ALTERNATIVE 1
«constant p and V imply» nT = const ✓
T increases hence n decreases ✓
ALTERNATIVE 2
«constant p and n imply» V is proportional to T / air expands as it is heated ✓
«original» air occupies a greater volume OR some air leaves through opening ✓
MP2 in ALT 2 must come from expansion of air, not from expansion of water.
Award [0] for an answer based on expansion of water.
Award [1] max for an answer based on convection currents.
It was surprising to see a large number of answers based on the expansion of water, as the stem of the question clearly states that the level of water remains constant. Most successful candidates scored by quoting pV constant so concluding with the inverse relationship of n and T, others also managed to score by explaining that the volume of air increases and therefore must go out through the opening. Answers based on convection currents were given partial credit.
