440 Rebbeca Liang.
Surface tension is responsible for the spherical shape of a bubble.
Surface tension is also responsible for the formation of spherical droplets, the rise of water in a capillary, and the movement of a liquid through a porous solid. The molecules at the surface of a liquid are attracted into the body of the liquid because the attraction of the underlying molecules is greater than the attraction by the vapour molecules on the other side of the surface. This inward attraction causes the surface to contract if it can and gives rise to a force in the plane of the surface. The surface tension of a liquid is the force per unit length on the surface that opposes the expansion of the surface area. The surface tension of a bubble acts so that the bubble has a natural tendency to contract and reduces its surface area.