A supercritical fluid is a fluid at temperature and pressure above its liquid-gas critical point. There is then no liquid–vapor coexistence boundary separating distinct bulk liquid and gas states. Density can change continuously from relatively gas-like to relatively liquid-like values along a suitable path.
This continuity does not mean that all supercritical states have identical properties. Density, compressibility, viscosity and solvent behavior can vary strongly, particularly near the critical region. Pressure can therefore tune a supercritical solvent's ability to dissolve material without crossing a boiling boundary. The absence of a liquid–vapor boundary applies to that transition; freezing or other transitions can still occur elsewhere in the phase diagram.
A supercritical fluid is a state of matter that occurs when a substance is subjected to temperatures and pressures above its critical point. At this state, the fluid exhibits properties of both liquids and gases. Specifically, supercritical fluids have the ability to diffuse through solids like a gas while also dissolving materials like a liquid. The critical point is the temperature and pressure at which the distinctions between liquid and gas phases become indistinguishable.
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