Cohesive and Adhesive Liquids

Cohesion and adhesion represent the result of intermolecular attractive forces acting between two adjacent portions of a substance, particularly of a solid or liquid, or two dissimilar substances. These forces originate principally because of electrical forces. When two molecules are close together, they are repelled; when farther apart, they are attracted; and when they are at an intermediate distance, their potential energy is at a minimum, requiring the expenditure of work to either approximate or separate them. Thus, work is required to pull apart two objects in intimate contact, whether they are of the same or different material.