Oberflächenspannungen

Oberflächenspannung is a physical 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, which are attracted to each other. At the surface of a liquid, molecules are pulled inwards by the bulk of the liquid, creating a net inward force. This inward force causes the surface to behave like a stretched elastic membrane, resisting external forces and minimizing its area.

The unit of surface tension is typically measured in Newtons per meter (N/m) or dynes per centimeter (dyn/cm). Several factors can influence surface tension, including temperature and the presence of solutes. Generally, surface tension decreases as temperature increases because molecular motion becomes more energetic, weakening the intermolecular forces. Dissolved substances can also alter surface tension. Surfactants, for example, are substances that significantly lower the surface tension of a liquid.

Surface tension is responsible for many observable phenomena. 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 a direct consequence of surface tension and adhesive forces between the liquid and the surface of the tube. Droplet formation, where liquids form spherical or near-spherical drops, is another manifestation of surface tension minimizing surface area. The way insects can walk on water is also attributed to surface tension, as their weight is not enough to break the surface.