A phase diagram shows the preferred physical states of matter at different temperatures and pressure. Within each phase the material is uniform with respect to its chemical composition and physical state. At typical temperatures and pressure (marked by an 'E' below) water is a liquid, but it becomes solid (i.e. ice) if its temperature is lowered below 273 K and gaseous (i.e. steam) if its temperature is raised above 373 K, at the same pressure.
