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JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Heat & Thermodynamics

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During the melting of a slab of ice at 273 K at atmospheric pressure :
  1. (A)Internal energy of ice-water system remains unchanged.
  2. (B)Positive work is done by the ice-water system on the atmosphere.
  3. (C)Internal energy of the ice-water system decreases.
  4. (D)Positive work is done on the ice-water system by the atmosphere.✓ Correct

Answer: (D)

Solution

When ice melts at constant temperature and pressure, its volume decreases (ice is less dense than water). Since the volume decreases, the atmosphere does positive work on the ice-water system: (work done on the system is positive). Heat is absorbed during melting, so . By the first law of thermodynamics, , meaning the internal energy increases. Therefore, positive work is done on the ice-water system by the atmosphere.

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Single correct option

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