Q 11-11-170JEE MainJEE Main 2025 (3 Apr, Shift 1)Medium
During the melting of a slab of ice at $273\ \text{K}$ at atmospheric pressure:
Answer: (D) Positive work is done on the ice-water system by the atmosphere.
Ice is less dense than water, so the volume **decreases** on melting. The atmosphere therefore pushes in and does positive work on the system (the work done by the system, $P\Delta V$, is negative).
Heat is absorbed ($Q > 0$) and work is done on the system, so by the first law $\Delta U = Q - W_{\text{by}} > 0$: the internal energy increases.
Only statement (4) is correct.
Solution by Sreeraj P, M.Sc Physics