During the melting of a slab of ice at 273 K at atmospheric pressure: (a) Internal energy of ice-water system remains unchanged. (b) Positive work is done by the ice-water system on the atmosphere. (c) Positive work is done on the ice-water system by the atmosphere. (d) Internal energy of the ice-water system decreases.

Answer: (c). Ice is less dense than water, so the volume decreases on melting. With Δ V < 0 at constant pressure, work done by the system PΔ V is negative, i.e. the atmosphere does positive work on the system. Latent heat is absorbed, so internal energy increases; (a) and (d) are wrong. So the answer is (c).

During the melting of a slab of ice at 273 K at atmospheric pressure: | JEE Main 2025 (3 Apr, Shift 1)

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Heat, Work & First Law of Thermodynamics

During the melting of a slab of ice at 273 K at atmospheric pressure:

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Answer: (c)

Ice is less dense than water, so the volume decreases on melting.
With $\Delta V < 0$ at constant pressure, work done by the system $P\Delta V$ is negative, i.e. the atmosphere does positive work on the system.
Latent heat is absorbed, so internal energy increases; (a) and (d) are wrong.
So the answer is (c).

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