The presence of 2 extra pairs of electrons on the oxygen in water molecule results in-

Though water molecule appears to be neutral, it is an electric dipole, i.e. have both positive and negative charges on the same molecule. The electric dipolar nature of the water molecule is due to its structure which consists of two hydrogen atoms linked covalently to an oxygen atom. Each of the hydrogen atom shares a pair of electrons with the oxygen atom. Oxygen has a strong electron - withdrawing tendency and therefore it pulls shared electrons away from the hydrogen nuclei to lie more towards oxygen. Consequently, hydrogen atom acquires a localized partial positive charge. Oxygen has two more pairs of electrons which remain unshared. These electrons impart a partial negative charge to oxygen.