MAE 241 Introduction to Thermodynamics Exam 1 Practice

At a fixed pressure, there is a specific temperature where liquid and vapor are in equilibrium—the boiling (saturation) temperature. If the vapor’s temperature is above that boiling point, it has more energy than needed for the phase change and becomes a superheated vapor. This state means the vapor is not at the boundary with liquid anymore and behaves like a gas with extra sensible heat.

Saturated vapor, by contrast, exists exactly at the boiling point for that pressure and is in balance with liquid. Sublimation is a solid-to-gas transition, not a description of the vapor’s temperature relative to boiling. Quality refers to the fraction of vapor in a liquid-vapor mixture, not to a single vapor state. For example, at 2 bar absolute, the saturation temperature is about 120°C; a vapor at 140°C at 2 bar is superheated.