For a given system, vapor pressure can be defined as the pressure exerted by the vapor phase in equilibrium with the condensed phase.
In this case, as water sits in an open beaker it tends to evaporate thereby forming water vapor. This vapor phase then exerts a pressure over the liquid water, which is termed as the vapor pressure of water at that temperature and pressure. As water continues to evaporate, more and more molecules escape into the vapor phase which thereby increases the vapor pressure.
Ans: The vapor pressure of water increases as the water evaporates.
