Critical line (thermodynamics)

In thermodynamics, a critical line is the higher-dimensional equivalent of a critical point.^[1] It is the locus of contiguous critical points in a phase diagram. These lines cannot occur for a single substance due to the phase rule, but they can be observed in systems with more variables, such as mixtures. Two critical lines may meet and terminate in a tricritical point.

References

1. ↑ B. Widom, Theory of Phase Equilibrium, J. Phys. Chem 1996, 13190-13199

States of matter
State	Solid Liquid Gas / Vapor Plasma
Low energy	Bose–Einstein condensate Fermionic condensate Degenerate matter Quantum Hall Rydberg matter Strange matter Superfluid Supersolid Photonic matter
High energy	QCD matter Lattice QCD Quark–gluon plasma Supercritical fluid
Other states	Colloid Glass Liquid crystal Quantum spin liquid Magnetically ordered Antiferromagnet Ferrimagnet Ferromagnet String-net liquid Superglass
Transitions	Boiling Boiling point Condensation Critical line Critical point Crystallization Deposition Evaporation Flash evaporation Freezing Chemical ionization Ionization Lambda point Melting Melting point Recombination Regelation Saturated fluid Sublimation Supercooling Triple point Vaporization Vitrification
Quantities	Enthalpy of fusion Enthalpy of sublimation Enthalpy of vaporization Latent heat Latent internal energy Trouton's ratio Volatility
Concepts	Binodal Compressed fluid Cooling curve Equation of state Leidenfrost effect macroscopic quantum phenomena Mpemba effect Order and disorder (physics) Spinodal Superconductivity Superheated vapor Superheating Thermo-dielectric effect
Lists	List of states of matter