Case study·Standard multi-step (3/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A teacher describes four processes. Process P: a gas expands very slowly through equilibrium states with negligible friction. Process Q: a gas expands suddenly into an evacuated chamber. Process R: two bodies at different temperatures are placed in contact. Process S: a gas returns to its initial state after a closed path.
Total: 4 marks
(a) Which process is closest to reversible? (1 mark)
(b) Which process is an example of free expansion? (1 mark)
(c) What is the net change in internal energy for process S? (1 mark)
(d) Which process shows spontaneous heat flow toward thermal equilibrium? (1 mark)
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