Definitions
Surface and interfacial tensions

The most common manifestations of surface tension are the formation of drops or gas bubbles rising in a liquid, the trickling of water over impermeable fabrics, for example, but also the penetration of liquids into narrow spaces. The rise of water in vertical tubes placed in water was already observed by Leonardo da Vinci. This phenomenon was called capillarity (from the Latin capillus, meaning hair); today, the word refers to all phenomena linked to the shape of a liquid surface.

Surface tension is defined as the force, existing at the surface of a liquid, due to the attraction between molecules that oppose surface rupture. Surface tension $\sigma$ is the tensile force acting on a surface element located in a plane tangent to the...