Saturated vapor pressure and atmospheric pressure
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The saturated vapor pressure is measured under constant temperature in a sealed environment; what happens to the medium if the space is not sealed, that is, if it is connected to the atmosphere? Taking ethanol as an example, it would gradually dissipate completely in an open environment. Well, here’s the problem: at temperatures below its boiling point, the saturated vapor pressure of ethanol is lower than atmospheric pressure. Can ethanol then transition from the liquid phase to the gas phase without any issue?
At 35 degrees, the saturated vapor pressure of ethanol is 13.3 kPa; in other words, when the partial pressure of ethanol in the air reaches 13.3 kPa, gas-liquid equilibrium for ethanol at that temperature is achieved. However, ethanol diffuses into the air, which reduces the partial pressure of ethanol at the ethanol-air interface, causing the ethanol to continue to evaporate until it is all gone. It’s similar to dropping ethanol on a table – it keeps evaporating until nothing remains
It will evaporate completely and turn entirely into a gas phase
The original poster knows too little about the concepts and properties of thermodynamics. The saturated vapor pressure is a function of temperature only and is not affected by the ambient pressure; that is, the saturated vapor pressure of ethanol in a vacuum is the same as that in an environment with a nitrogen pressure of 10 MPa. As long as it is an open system, no matter what the system pressure is, ethanol will evaporate completely given enough time. The same applies to water and other liquids as well.
Gas-liquid equilibrium, basic concepts
Like air, it will of course gradually evaporate away
Well, it will keep evaporating until the partial pressure in the air equals the saturated vapor pressure at that temperature, or until it has completely evaporated^_^