Water as a polar molecule

Because it’s polar, water has a tendency to “wet” substances, like grandma’s fine dining-room table or a baby’s diaper. It’s also a bent molecule , not linear. The hydrogen atoms have a partially positive charge (+); the oxygen atom has a partially negative charge (–). This charge distribution is due to the electronegativity difference between hydrogen and oxygen atoms (the attraction that an atom has for a bonding pair of electrons). The water molecule in Figure 2-1 is shown in its bent shape with a bond angle of about 105°.
Normally, such partial charges result in an intermolecular force known as a dipole-dipole force, in which the positive end of one molecule attracts the negative end of another molecule. The very high electronegativity of oxygen combined with the fact that a hydrogen atom has only one electron results in a charge difference significantly greater than you’d normally expect. This leads to stronger-than-expected intermolecular forces. These unexpectedly strong intermolecular forces have a special name: hydrogen bonds. The term hydrogen bond doesn’t refer to an actual bond to a hydrogen atom, but to the overall interaction of a hydrogen atom bonded to either oxygen, nitrogen, or fluorine atoms with an oxygen, nitrogen or fluorine on another molecule (intermolecular) or the same molecule (intramolecular). Hence the term intermolecular force. (Note that although hydrogen bonds occur when hydrogen bonds to fluorine, you don’t normally find such combinations in biological systems.)