The volume change from liquid to gas is very large

Scientific Explanation

When any liquid vaporizes, its volume increases substantially — that much is normal. For water, however, the expansion is extraordinarily large. One liter of liquid water produces approximately 1,600 liters of steam at atmospheric pressure — a volume increase by a factor of 1,600. By comparison, ethanol expands by a factor of about 500, and acetone by roughly 300.

The reason for this extreme volume change lies in the compact structure of liquid water, held together by hydrogen bonds. In the liquid, these bonds keep molecules closely packed, producing a relatively high density for such a lightweight molecule. Upon vaporization, not only van der Waals forces but also these strong hydrogen bonds must be overcome. In the gas phase, molecules are fully separated and occupy an enormous volume.

The large volume change is closely connected to water’s high enthalpy of vaporization: substantial energy is required to break the hydrogen bond network, and the resulting gas has very low density.

Everyday Relevance

This enormous volume change makes steam an exceptionally effective working fluid. Steam engines and turbines in power plants exploit precisely this effect: a relatively small quantity of water produces a vast volume of steam that drives turbines. Pressure cookers and espresso machines operate on the same principle.

In nature, the large volume change is relevant for volcanism (water in magma vaporizes explosively) and cloud formation (evaporating water carries large amounts of energy into the atmosphere).