Question

Water is considered a polar molecule because _____.

Answer 1

Water is polar because of the difference in electronegativity between hydrogen and oxygen. The highly electronegative oxygen atom attracts electrons or negative charge to it, making the region around the oxygen more negative than the areas around the two hydrogen atoms.
http://chemistry.about.com/od/waterchemistry/f/Why-Is-Water-A-Polar-Molecule.htm

Answer 2

oxygen is more electronegative than hydrogen, u call them"dipole molecule," making the oxygen slightly negative because of the unequal sharing of electrons. This makes the hydrogen slightly positive since the oxygen atom is more electronegative ; the electrons spend more time orbiting the oxygen than they do the hydrogens. Therefore the oxygen is slightly (or delta) negative and the hydrogen, since the electrons spend less time in orbit around the hydrogen, is delta (slightly) positive since an electron has a negative charge.

O-H bonds are polar because O and H have different electronegativity values. The vector sum of the two bond dipoles is nonzero. (That is, they are not pointing in exact opposite directions.)