Why do simple covalent molecules have low boiling points even though they consist of strong covalent bonds?

Even though simple covalent molecules consist of strong covalent bonds, these bonds are NOT broken when the substance is heated. Upon heating, the forces between the simple molecules (known as intermolecular forces) are weakend. However, because simple molecules are so small, these forces are weak and therefore don't need much energy to overcome. This is why simple molecules have low boiling points.