Chemistry · THERMODYNAMICS

In an isolated system containing liquid water in equilibrium with its vapor at \( 100^\circ\text{C} \), if the volume of the container is suddenly doubled, which of the following is true regarding \( \Delta U \) of the isolated system immediately after the expansion?

1. \( \Delta U = 0 \) because no energy as heat or work can cross the boundary of an isolated system.
2. \( \Delta U > 0 \) because vaporization is an endothermic process.
3. \( \Delta U < 0 \) because the system expands against vapor pressure.
4. \( \Delta U = w_{\text{ad}} \neq 0 \) because boundary work is performed on the walls.