Cohesion and Adhesion

The molecules of this liquid form a bubble because they are alike.

Cohesion is the intermolecular attraction between similar molecules. This force is strongest in solids, weaker in liquids, and weakest in gases. Examples: droplets of water and gas clouds.


Duct tape is an example of chemical adhesion.

Adhesion is the intermolecular attraction between unlike molecules. Mechanical adhesion refers to two materials sticking together through interconnecting surfaces. Chemical adhesion occurs when the surfaces of two materials combine through its molecules exchanging or sharing electrons. The two surfaces of a chemical bond must be brought and held close together. Electrostatic adhesion is the attraction between two surfaces with different electrical charges. Dispersive adhesion is explained through van der Waals forces, that molecules may be held together if they are positively and negatively charged. Diffusive adhesion is the joining of molecules that are soluble in each other. Example: duct tape, paste, Velcro, and paper sticking to a television.