At room temperature, water is a liquid with a molar volume of 18 \(\mathrm{mL}\) . At \(105^{\circ} \mathrm{C}\) and 1 atm pressure, water is a gas and has a molar volume of over 30 \(\mathrm{L}\) . Explain the large difference in molar volumes.

The large difference in molar volumes of water at room temperature (liquid state) and at 105°C and 1 atm pressure (gaseous state) can be explained by the changes in intermolecular forces during the phase transition. In its liquid state, water molecules are held closely together by hydrogen bonding, resulting in a smaller molar volume (18 mL). When the temperature is raised and water becomes a gas, hydrogen bonding is no longer effective, causing the water molecules to be much more dispersed and leading to a significantly larger molar volume (over 30 L). The increase in kinetic energy and the breaking of intermolecular forces result in a much larger separation between molecules in the gaseous state compared to the liquid state.