What characterizes a saturated vapor?

A saturated vapor is characterized by being in equilibrium with its liquid form. This means that at a specific temperature and pressure, the rate at which molecules are evaporating from the liquid phase is equal to the rate at which they are condensing back into the liquid phase. This dynamic equilibrium allows for a stable concentration of vapor in the air above the liquid.

When a vapor is saturated, it has reached the maximum concentration of vapor that can exist at that temperature and pressure without further condensation occurring. If more vapor is added to this system, it will begin to condense into a liquid. Thus, option B correctly captures the essence of a saturated vapor by emphasizing the balance between evaporation and condensation.

In contrast, other choices reflect misunderstandings of the properties of saturated vapors. For instance, a saturated vapor cannot hold more vapor without condensation (as indicated in the first choice), and it is definitely influenced by temperature—raising the temperature can increase the saturation pressure and the amount of vapor that can exist. Finally, while saturated vapors can exist at varying pressures, they do not necessarily have a higher pressure than the surrounding atmospheric pressure; their relationship to atmospheric pressure depends on the specific conditions.