States of matter. Illustration showing three states of matter for water; solid (ice), liquid (water) and gas (steam). The state of matter (or phase) of a substance depends on the ambient temperature and pressure. At any combination, there is a dynamic equilibrium between two or more phases. Water at a temperature of 0. 072 Celsius and an ambient pressure of 612 Pascal has a dynamic equilibrium between all three phases - this is known as its triple point. A fourth phase, the plasma, exists at extremely high temperatures and is normally seen only in elements.