The bonding force between a polymer of n molecules in liquid A, (A)ln, is subject to an internal tension, τAn, attributable to the polymers of all sizes in liquid A. This tension exceeds the internal tension between pure polymer (A)lon, τ0An, and this enhanced tension, πAn=τAN—τAn, changes all partial molar quantities of (A)lnwithin liquid A with respect to the molar quantities of pure (A)lon, including the chemical potential of polymer (A)ln(such that μlAn(T, pl, xlAn) is equal to μloAn(T,pl—πAn)). When the vapor of A is in equilibrium with liquid A, the vapor of (A)nmust also be in equilibrium with liquid (A)nfor every n from 1 to N. Even when the mole fraction of polymer (A)lnis altered by changing the pressure applied to liquid A, its mole fraction must equal the mole fraction of (A)vnin the vapor phase with which it is in equilibrium, i.e., xlAn=xlAnfor an)T or pv. Since water vapor is monomeric, liquid water must also be monomeric.