Why is water a polar molecule?

Water is a polar molecule due to the combination of its specific bond characteristics and its molecular geometry.

Each oxygen-hydrogen bond in a water molecule is polar because oxygen has a higher electronegativity than hydrogen. This causes the oxygen atom to attract the shared bonding electrons more strongly, resulting in a partial negative charge on the oxygen and a partial positive charge on the hydrogen atoms.12

While the presence of polar bonds is necessary, a molecule's overall polarity also depends on its shape. Unlike linear molecules such as carbon dioxide, where bond dipoles cancel each other out, the water molecule is bent at an angle of 104.5°. Because of this angular geometry, the individual bond dipole moments do not cancel, resulting in a nonzero net electric dipole moment for the molecule as a whole.123