How much work is done by the steam when $1.00 \mathrm{~mol}$ of water at $100^{\circ} \mathrm{C}$ boils and becomes $1.00 \mathrm{~mol}$ of steam at $100^{\circ} \mathrm{C}$ and at $1.00$ atm pressure? Assuming the steam to be an ideal gas, determine the change in internal energy of the steam as it vaporizes.