The relationship between surface tension and the shape of a liquid drop is fundamentally linked to the minimization of free energy, which favors a spherical shape in the absence of gravity due to positive interfacial energy. In contrast, negative interfacial energy promotes mixing and increases interfacial area. The discussion highlights that the atomic origins of interfacial energy are complex, but the focus can remain on the concept of dividing surfaces without delving into atomic details. When a drop is on a surface, both cohesion (intermolecular attractions within the liquid) and adhesion (attraction between the liquid and the surface) play crucial roles. The contact angle is a key factor; a higher attraction between the liquid molecules and the surface results in a less spherical shape, emphasizing the importance of these forces in determining the drop's geometry.
