Critical point

Definition

The critical point is the temperature and pressure at which the liquid and gas phases of a substance become indistinguishable. At this point, the properties of the liquid and gas phases converge into a single phase called a supercritical fluid.

5 Must Know Facts For Your Next Test

1. At the critical point, the density of the liquid phase equals the density of the gas phase.
2. The critical temperature is the highest temperature at which a substance can exist as a liquid, regardless of pressure.
3. Critical pressure is the minimum pressure required to liquefy a substance at its critical temperature.
4. Supercritical fluids have unique properties that are different from both liquids and gases.
5. Water's critical point occurs at approximately 374°C and 22.1 MPa.

Review Questions

• What happens to the properties of a substance at its critical point?
• Why is it impossible to distinguish between liquid and gas phases beyond the critical point?
• What are supercritical fluids, and how do they differ from ordinary liquids and gases?

Related terms

Phase Diagram: A graphical representation showing the different states of matter (solid, liquid, gas) of a substance as a function of temperature and pressure.

Triple Point: The specific temperature and pressure where all three phases (solid, liquid, gas) coexist in equilibrium.

Latent Heat: \(\text{The amount of heat absorbed or released during a phase change without changing temperature.}\)