A capillary tube is partially filled with liquid water at 40C, evacuated to remove all air, and sealed, after which the liquid fills 20% of the tube (by volume). The tube is then gradually heated until a temperature is reached for which the vapor-liquid interface in the tube disappears. a) Use information from the steam tables and your understanding of the P-V behavior of pure fluids to estimate the pressure at which the interface disappears from the tube. At that point, is the phase a liquid or a vapor? b) Repeat (a) for the case where the tube is initially filled 50% of the way with liquid water at 20C