Uses Of Electronegativity Values - To Predict Polarity Of Covalent Bonds

Question 1

How can some molecules that are polar covalent bonds not be polar?

Answer 1

They can be symmetrical molecules.
The polar molecules have centres of partial positive charge and centres of partial negative charge that coincide, i.e. the polarities of the bonds cancel each other out due to the symmetry of the molecules.

Question 2

Why is a water molecule polar?

Answer 2

The V-shape means that the partial positive and negatives charges do not cancel out and hence water is a polar molecule.