The critical temperature of a liquid is the greatest temperature at which a liquid and its vapor can exist in equilibrium. Beyond this temperature, no amount of pressure will allow the chemical to exist as a liquid. It is an important notion in understanding phase transitions, especially for liquids and gases, because it denotes the point at which the distinction between liquid and gaseous phases disappears.
Density Convergence: As the critical point approaches, the densities of the liquid and vapor phases converge, becoming almost identical.
Compressibility: The liquid phase, which is generally incompressible, becomes more compressible around its critical temperature
Thermal Expansion: The thermal expansion coefficient, which is usually low for liquids, rises dramatically.
Dielectric Properties: As liquid and vapor grow more similar in molecular structure, the substance’s capacity to operate as a dielectric (electric current insulator) decreases.
Solvent Properties: As the liquid approaches the critical point, it becomes a poor solvent for electrolytes (ions and polar substances) and begins to dissolve more nonpolar gasses and organic molecules with ease.