What explains the concept of surface tension in liquids?

Surface tension in liquids is primarily explained by the attraction between molecules of the same substance, a phenomenon known as cohesion. In a liquid, molecules are attracted to each other due to intermolecular forces, such as hydrogen bonding in water. This cohesive force causes the molecules at the surface to experience a net inward force since they are only partially surrounded by other liquid molecules, which creates a sort of "film" at the surface that resists external force.

This cohesive property leads to various observable phenomena, such as the ability of small objects to float on the surface (despite being denser than the liquid) and the formation of spherical droplets, as the surface tension minimizes the surface area. The cohesive attraction also explains why liquids tend to minimize their surface area, forming droplets rather than spreading out in a thin layer.

The other concepts mentioned do not accurately capture the essence of surface tension. For example, magnetic attraction among molecules does not play a role in typical liquid interactions, and repulsion between non-polar molecules would involve different principles of molecular forces that are not pertinent to surface tension. Similarly, the equality of thermal properties does not describe the molecular interactions that result in surface tension.