What does the critical pressure of a substance indicate?

The critical pressure of a substance indicates the pressure above which a liquid cannot become a vapor by adding heat, regardless of how much heat is applied. At this pressure, the substance exists in a supercritical state where distinct liquid and gas phases do not exist. Therefore, beyond the critical point, increasing temperature does not result in the formation of vapor; instead, the properties of the substance change significantly.

Understanding this concept helps in various refrigeration applications, as it determines the operating limits of refrigerants. When designing or troubleshooting refrigeration systems, an awareness of the critical pressure informs decisions about efficiency and performance under varying thermal and pressure conditions.