Different States of Water

As with most substances, water can exist in three states or phases: solid (ice), liquid (water itself), and gas (water vapor).

In the case of water, these three phases coexist in nature (it is the only substance on Earth with this property), always observable in pairs and more or less in equilibrium: water-ice, ice-vapor, and water-vapor, depending on temperature and pressure conditions. The corresponding equilibrium curves can be seen in Figure 4 (phase diagram or phase-change diagram), which graphically illustrates the temperature and pressure conditions under which the three phases of water exist, as well as their respective...