Question

How can a non-polar molecule contain polar bonds?

Answer 1

It's all because of electronegativity.

Explanation:

I'll use an example.

Lets say you have a linear shaped molecule. In this case, I'm using CO2.

NOTE: Linear refers to the way that the atoms form a line with an angle of 180 degrees.

Now, you can see that there are no electrons around the central atom. Instead, they are on the outside atoms.

So this means that both sides of the molecule are negatively charged. Meaning the molecule is non-polar because we're missing one side having a positive charge.

If we look at just the bond between the carbon and the oxygen, then we see a polar bond. This is because oxygen is slightly more electronegative than carbon.

So the electrons in the bond are pulled slightly more towards the oxygen atom, giving it a negative charge and giving the carbon a slightly positive charge because electrons are being pulled away from it.

NOTE: Electronegativity = how much an atom 'wants' electrons

In Summary:
The overall atom is non-polar because there are two negatively charged sides instead of one positive side and one negative side.

The bonds in the molecule are polar because electronegativity causes one side of the bond to be positive and the other side to be negative.