QUESTION PAPER 1

Chapter 11: Thermodynamics

Original chapter-specific practice paper

Maximum Marks: 40Suggested time: 60 minutes

Instructions: Answer all 20 questions. Marks are shown in brackets. Show calculation steps and units. These are original practice questions, not an official examination paper.

Section A · 1-mark questions — 8 × 1 = 8 marks

State the zeroth law.[1]
Define internal energy.[1]
First law with W done by system?[1]
Meaning of adiabatic?[1]
Meaning of isothermal?[1]
Can a cyclic heat engine be 100% efficient?[1]
Ideal gas equation?[1]
Carnot efficiency?[1]

Section B · 2-mark questions — 6 × 2 = 12 marks

At constant volume, 500 J heat added: work?[2]
Gas absorbs 800 J and does 300 J work: ΔU?[2]
Carnot T_h=600K,T_c=300K: efficiency?[2]
Ideal-gas isothermal process: ΔU?[2]
1 mol with C_v=20 J/mol K and ΔT=5 K: ΔU?[2]
Isothermal versus adiabatic?[2]

Section C · 3-mark questions — 4 × 3 = 12 marks

Gas absorbs 1000 J and does 400 J work: ΔU?[3]
Carnot T_h=500K,T_c=300K: η?[3]
Isobaric gas expands .01 to .03 m³ at 100 kPa. Work?[3]
Why no real cyclic engine converts all heat to work?[3]

Section D · 4-mark questions — 2 × 4 = 8 marks

Explain reversible and irreversible processes with examples.[4]
Engine absorbs 1500 J from 600K, rejects to 300K; actual work=500J. Find Carnot limit, actual efficiency and Qout.[4]

End of paper — review signs, units and working.

Open marking scheme and model answers

Attempt the paper before opening the key. Model answers show the expected facts and results; mark allocation is a suggested guide and equivalent correct methods should receive credit.

Q1 · 1 mark
Thermal equilibrium is transitive.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q2 · 1 mark
Microscopic energy of molecules and their interactions.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q3 · 1 mark
Q=ΔU+W.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q4 · 1 mark
Q=0.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q5 · 1 mark
Temperature constant.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q6 · 1 mark
No.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q7 · 1 mark
pV=nRT.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q8 · 1 mark
1−T_c/T_h.
1 mark for the correct fact, unit or formula. Accept an equivalent correct method.

Q9 · 2 marks
Zero boundary work.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q10 · 2 marks
500 J.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q11 · 2 marks
50%.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q12 · 2 marks
Zero.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q13 · 2 marks
100 J.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q14 · 2 marks
Isothermal: T constant; adiabatic: Q=0.
Suggested split: 1 mark for the principle/formula and 1 for the answer or explanation. Accept an equivalent correct method.

Q15 · 3 marks
600 J.
Suggested split: 1 for the relation, 1 for working/reasoning and 1 for result with unit. Accept an equivalent correct method.

Q16 · 3 marks
40%.
Suggested split: 1 for the relation, 1 for working/reasoning and 1 for result with unit. Accept an equivalent correct method.

Q17 · 3 marks
W=pΔV=2000 J.
Suggested split: 1 for the relation, 1 for working/reasoning and 1 for result with unit. Accept an equivalent correct method.

Q18 · 3 marks
Second law requires rejected heat or other entropy increase.
Suggested split: 1 for the relation, 1 for working/reasoning and 1 for result with unit. Accept an equivalent correct method.

Q19 · 4 marks
Reversible: ideal quasi-static frictionless; irreversible: friction or finite-temperature heat flow.
Suggested split: 1 for principle, 1 for equation, 1 for working and 1 for result/explanation. Accept an equivalent correct method.

Q20 · 4 marks
Carnot limit 50%; actual efficiency 33.3%; Qout=1000 J.
Suggested split: 1 for principle, 1 for equation, 1 for working and 1 for result/explanation. Accept an equivalent correct method.