Which term describes a condition of stable equilibrium of vapor and liquid?

The term that describes a condition of stable equilibrium of vapor and liquid is saturation. In the context of thermodynamics and phase change, saturation refers to the point at which a liquid and its vapor are in balance; meaning that the rate of evaporation of the liquid equals the rate of condensation of the vapor. This occurs at specific temperature and pressure conditions for each substance, providing a consistent and stable state.

When a system is at saturation, any heat added to the system can increase the temperature, or it can cause a phase change, but the proportions of liquid and vapor remain consistent until the equilibrium is disturbed. This concept is crucial in understanding how refrigerants operate within air conditioning systems and the principles behind various thermodynamic cycles.

In contrast, condensation involves the process by which vapor turns into liquid, implying a transition that disrupts equilibrium, whereas vaporization and evaporation specifically refer to the processes of liquid turning into vapor, which takes the system away from a state of saturation. Thus, saturation is the proper term for stable equilibrium between vapor and liquid phases.