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Fluids

Phase diagram


Substances normally can appear in three different phases (states): solid, liquid and gas (vapor).
Their state depends on temperature and pressure.

Schematic appearance of a phase diagram that shows for which combination of temperature and pressure a substance appears in which state.

In the past physicists and chemists have made diagrams, phase diagrams, for many different substances, as for example water, where it is indicated, as in the schematic figure above, at which combination of temperature and pressure the substance appears as a solid, a liquid or a gas. The fat black lines indicate where transitions from one phase to the other take place.

phase transitions