ESS Regents Practice Exam

Water is polar because its electrons are shared unevenly. Oxygen is more electronegative than hydrogen, so it pulls electron density toward itself, giving the molecule a bent shape with a partial negative charge on the oxygen end and partial positive charges on the hydrogen ends. This creates a dipole moment, a situation where one side of the molecule is slightly negative and the other slightly positive. That separation of charge explains why water interacts strongly with other polar substances and ions, helping it dissolve many of them. The description of having a slightly negative side and a slightly positive side best captures this idea. The other statements—being nonpolar, having no charge separation, or being unable to dissolve polar substances—don’t fit water’s actual behavior.