What happens to the liquid phase at the critical temperature?

At the critical temperature, the properties of the liquid and vapor phases become indistinguishable. This means that the liquid phase fundamentally changes as the temperature is increased beyond this point. The critical temperature is the highest temperature at which a substance can exist as a liquid, regardless of the pressure applied. Therefore, as a substance reaches its critical temperature, it cannot remain in the liquid phase; instead, the liquid phase effectively disappears, and the substance transitions into a supercritical fluid.

In supercritical fluids, there is no clear distinction between the liquid and gas phases, which is a unique state of matter that exhibits properties of both phases. This transition at the critical temperature is a crucial concept in thermodynamics and physical chemistry, particularly in understanding phase diagrams and behaviors of substances under varying conditions of temperature and pressure.