Internal energy — UPSC Physics Optional IFoS 2025 Paper I

One gram of water (1\text{ cm}^3) becomes 1671\text{ cm}^3 of steam when boiled at constant pressure of 1\text{ atm} (1\cdot 013 \times 10^5\text{ Pa}). The heat of vapourisation at this pressure is \text{L} = 2\cdot 256 \times 10^6\text{ J/kg}. Calculate :

(i) The work done by the water when it vapourizes, and

(ii) Increase in its internal energy.