1. The problem statement, all variables and given/known data Imagine that all the molecular dipoles in a cup of water could be made to point down. Calculate the magnitude of the resulting surface charge density at the upper surface of the water, and express it in electrons per square centimeter. 2. Relevant equations 3. The attempt at a solution Can I just find the number of water molecules per square centimeter of area, knowing the approximate size of an H2O molecules, and then say that since all the dipoles point down we will have 2 electrons for every such molecule along the surface?