Question

Why is water considered a polar molecule?

Answer 1

Short answer: Because the O–H bonds are polar (oxygen is much more electronegative than hydrogen) and the molecule’s bent shape prevents the bond dipoles from canceling, so water has a net dipole moment.

Explanation:
- Electronegativity: Oxygen pulls shared electrons toward itself more strongly than hydrogen does, so each O–H bond has a dipole with a partial negative charge (δ–) on oxygen and partial positives (δ+) on the hydrogens.
- Geometry: Water’s electron geometry is roughly tetrahedral (oxygen has two bonding pairs and two lone pairs). The molecular shape is bent (H–O–H ≈ 104.5°), not linear.
- Vector addition: The two bond dipoles point toward the oxygen and, because of the bent angle, they add together rather than cancel. That gives water a net dipole moment (~1.85 Debye) pointing from the hydrogens toward the oxygen.

Consequences: The polarity explains water’s hydrogen bonding, high boiling point, excellent solvent ability for ionic and polar substances, high surface tension, etc.

Contrast: In CO2 the bonds are polar but the molecule is linear, so the bond dipoles cancel and CO2 is nonpolar — illustrating that both bond polarity and molecular shape determine overall polarity.