<unk> , abbreviated as VLE by some, is a condition where a<unk>  and its<unk>  (gas phase) are in<unk>  with each other, a condition or state where the rate of<unk> ation<unk>  changing to<unk>  equals the rate of condensation<unk>  changing to<unk>  on a molecular level such that there is no net (overall)<unk><unk>  interconversion.  Although in theory<unk>  takes forever to reach, such an<unk>  is practically reached in a relatively closed location if a<unk>  and its<unk>  are allowed to stand in contact with each other long enough with no interference or only gradual intereference from the outside.
Vapor-liquid equilibrium
Electrochemical gradient
Chemical polarity
Isothermal process
Heat transfer
Pressure gradient 
Fluency
Exothermic reaction