Question

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

• A. Positive work is done by the ice-water system on the atmosphere
• B. Positive work is done on the ice-water system by the atmosphere
• C. The internal energy of ice-water system increases
• D. The internal energy of the ice-water system decreases

Answer 1

Answer: (B), (D)

Positive work is done on the ice-water system by the atmosphere
The internal energy of the ice-water system decreases

In melting Ice to water , heat $Q$ is supplied by air $[Q>0]$

Ice is less dense than water , so when ice melts, its intermolecular distances decreases resulting in lowering of internal energy [ $\Delta$u < 0]

Thus, as $W=Q-\Delta u$, from above , $\Rightarrow$ work done by air is positive.