Intermolecular forces: dipole-dipole, London dispersion force

In chemistry, it is important to understand how molecules interact with each other. These interactions are governed by forces known as intermolecular forces. Intermolecular forces are the forces that hold molecules together. They are responsible for many physical properties such as boiling point, melting point, and solubility. In this detailed explanation, we will explore two important types of intermolecular forces: dipole-dipole forces and London dispersion forces.

What are intermolecular forces?

Intermolecular forces are forces of attraction between molecules. They are much weaker than the strong chemical bonds that hold molecules together, but they play an important role in the behavior of substances.

1. Dipole-dipole force

Dipole-dipole forces occur between molecules that have permanent dipoles. These are polar molecules where one end of the molecule is slightly positive and the other end is slightly negative. This is due to the difference in electronegativities (the ability of an atom to attract electrons).

How do dipole-dipole forces work?

Imagine two water molecules (H2O). Each water molecule has a bent shape, and the oxygen atoms are more electronegative than the hydrogen atoms. This creates a dipole moment. The slightly positive hydrogen end of one water molecule is attracted to the slightly negative oxygen end of a nearby water molecule.

   H
  ,
 O -- H+ 

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