Critical point

Definition

The critical point is the end point of a phase equilibrium curve, where the properties of gas and liquid phases become indistinguishable. It represents the highest temperature and pressure at which a substance can exist as a liquid and gas in equilibrium.

5 Must Know Facts For Your Next Test

1. The critical point is characterized by a specific critical temperature and critical pressure.
2. At the critical point, the density of the liquid phase equals the density of the vapor phase.
3. The meniscus separating liquid and gas phases disappears at the critical point.
4. Above the critical temperature, no amount of pressure can liquefy a gas.
5. Every substance has its unique set of critical values.

Review Questions

• What happens to the distinction between liquid and gas phases at the critical point?
• Why can't a gas be liquefied above its critical temperature?
• What are two key properties that define a substance's critical point?

Related terms

Phase Diagram: A graph showing the conditions of temperature and pressure under which distinct phases occur and coexist at equilibrium.

Triple Point: The condition on a phase diagram where three phases (solid, liquid, and gas) coexist in equilibrium.

Supercritical Fluid: A state of matter beyond its critical point where distinct liquid and gas phases do not exist.