In an open pot,the molecules of water can get the kinetic energy to free themselves from the intermolecular force and evaporate from the air molecules that are over the surface of the water are bumping into the water molecules. I suppose , If the air pressure decreases,the air molecules will bump less frequently into the water molecules.In that case water molecules should take more time to get that necessary kinetic energy to free themselves. If my assumption is correct,shouldn't the water evaporation rate be lower? Please correct me if my assumptions are inccorrect. Thank you.
The water molecules get the kinetic energy to break the vapor barrier by bumping into other water molecules, not air molecules. Lower air pressure causes less exertion on the surface and lets the water molecules break the vapor barrier easier, thereby speeding up evaporation. You might want to read https://en.wikipedia.org/wiki/Evaporation#Factors_influencing_the_rate_of_evaporation