Here's why:

* Electronegativity: Oxygen is more electronegative than hydrogen. Electronegativity is the ability of an atom to attract electrons towards itself in a chemical bond.

* Electron Sharing: In the H-O bond, oxygen attracts the shared electrons more strongly than hydrogen. This means the electrons spend more time around the oxygen atom.

* Partial Charges: As a result of this unequal electron sharing, oxygen develops a partial negative charge (δ-) and hydrogen develops a partial positive charge (δ+).

This unequal distribution of charge creates a polar covalent bond in the water molecule.