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Name: Unknown
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993


Question:
It takes an input of energy to convert liquid to vapor, thus increasing entropy. If an increase in entropy is natural, why does this not happen naturally with less effort on its own?



Replies:
Actually, if you put a bowl of water in a room that was completely empty (no air either - although really the main condition is that there be no water vapor in the room to start with) then the water actually does naturally evaporate until there is a balance between the amount of water vapor and the temperature of the water (basically, it has a natural "vapor pressure" that it tries to achieve, for any given temperature). If the room is big enough, all the water will evaporate with no additional energy input. Depending on the circumstances, the average temperature of the water will also go down in this process, although that is a somewhat separate issue. The higher the water temperature, the higher the vapor pressure. There is actually a concept called "free" energy, which takes into account the entropy, so that any system tries to minimize its free energy - there is a balance between maximizing entropy and going into a higher energy state (the vapor as opposed to the liquid) - the whole field of thermodynamics is based on understanding these rather complex relationships.

A. Smith



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