Question

The hydrogen bond between two water molecules arises because water is what?

Answer 1

Because the water molecule is polar, i.e. electron density is unequally shared within the molecule.

Explanation:

The water molecule is polar: i.e. `""^(delta+)H-O^(delta-)-H^(delta+)` is a reasonable representation of this polarity, this charge separation.

Hydrogen bonding arises because of this polarity; i.e. alignment of the individual `O-H` dipoles. This acts as an extra intermolecular interaction. Such hydrogen bonding also occurs where hydrogen is bound to other strongly electronegative elements, i.e. `H-F`, and `NH_3` also exhibit some degree of polarity, and intermolecular hydrogen bonding occurs.