Hydrogen bonds vary in strength from about 4 to 40 kJ/mol. Given that the hydrogen bonds between water molecules are at the high end of this range, how does the strength of a hydrogen bond between water molecules compare with the strength of a H-O covalent bond within a water molecule? Do the values bear out the assertion that hydrogen bonds are about one tenth as strong as covalent bonds? How does such a 'weak' force strongly influence the properties of a hydrogen bonding substance?