The critical temperature of a substance is the maximum temperature at which it can exist in the liquid state, regardless of how much pressure is applied.
Key details:
- Above this temperature, the kinetic energy of the molecules is too high for intermolecular forces to hold them together in a liquid.
- Even if you increase the pressure, the substance will not condense into a liquid—it becomes a supercritical fluid instead.
Examples:
- For water, the critical temperature is about 374°C.
- Carbon dioxide’s critical temperature is about 31°C, which is why it cannot be liquefied at room temperature no matter how high the pressure.
Understanding critical temperature is vital in thermodynamics, chemical engineering, and supercritical fluid extraction, where substances above their critical point behave with properties of both gases and liquids.