Definition of critical point

1) The critical point in thermodynamics is the temperature and pressure at which the gas and liquid phases of a substance become identical and form a single phase.

At this point, properties like density and enthalpy become continuous across the gas and liquid states. The substance at its critical point is called a supercritical fluid, exhibiting properties of both a gas and a liquid.

Category/Context: Physical Chemistry, Thermodynamics, Phase Transitions

Related Terms: Supercritical Fluid, Phase Diagram, Critical Temperature, Critical Pressure, Triple Point

Examples/Applications: Supercritical fluids, existing beyond the critical point, have unique properties useful in various industries. For instance, supercritical carbon dioxide is used for decaffeination in the coffee industry and as a solvent in dry cleaning.

Student: This definition is suitable for undergraduate and graduate chemistry students.

Etymology/History: The concept of the critical point was developed in the 19th century with the advent of thermodynamics and the study of phase transitions.

source: Definition and meaning of Critical Point: Discover the unique state where a substance's gas and liquid phases merge, forming a supercritical fluid with intriguing properties.


  1. Critical point | phase change. (n.d.). Encyclopedia Britannica - Link
  2. Critical Point. (n.d.). Chemistry LibreTexts. Link