Answer:
Molecules cohere even though their ability to form chemical bonds has been satisfied. The evidence for the existence of these weak intermolecular forces is the fact that gases can be liquefied, that ordinary liquids exist and need a considerable input of energy for vaporization to a gas of independent molecules, and that many molecular compounds occur as solids. The role of weak intermolecular forces in the properties of gases was first examined theoretically by the Dutch scientist Johannes van der Waals, and the term van der Waals forces is used synonymously with intermolecular forces. Under certain conditions, weakly bonded clusters of molecules (such as an argon atom in association with a hydrogen chloride molecule) can exist; such delicately bonded species are called van der Waals molecules.
