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

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

Solution

Volume decreases during melting of ice so positive work is done on ice water system by atmosphere
Heat absorbed by ice water so $\Delta \mathrm{Q}$ is positive, work done by ice water system is negative
Hence by first law of thermodynamics
$\Delta \mathrm{U}=\Delta \mathrm{Q}+\Delta \mathrm{W}=\text { Positive }$
So internal energy increases

Asked in: JEE Main 2025 (03 Apr Shift 1)

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