Yfirborðsspenna

Yfirborðsspenna, or surface tension in English, is a property of liquids that describes the tendency of liquid surfaces to shrink into the minimum surface area possible. It arises from the cohesive nature of liquid molecules. Within the bulk of the liquid, molecules are attracted equally in all directions by neighboring molecules. However, at the surface, molecules are attracted inwards by the molecules below them and to the sides, but not by the gas or vacuum above. This imbalance of forces creates a net inward pull, causing the surface molecules to be held more tightly together.

This phenomenon is responsible for many observable effects. For instance, it allows small insects to walk on water, as their weight is not enough to break the surface tension. It also causes liquids to form droplets, as the spherical shape minimizes surface area for a given volume. Capillary action, the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity, is also a direct result of surface tension working in conjunction with adhesive forces between the liquid and the surface it is in contact with. Surface tension is measured in units of force per unit length, or energy per unit area. It is an important factor in various natural processes and industrial applications, including the behavior of water in soils, the formation of foams, and the design of microfluidic devices.