Kapillaariilmiö

Kapillaariilmiö, often translated as capillary action, describes the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. This phenomenon is driven by a combination of intermolecular forces: adhesion between the liquid and the solid surface of the capillary, and cohesion within the liquid itself. When adhesion is stronger than cohesion, the liquid will "climb" the walls of the capillary tube. The narrower the tube, the higher the liquid will rise, as the surface tension forces become more dominant relative to the weight of the liquid column.

The extent to which a liquid rises in a capillary is determined by the liquid's surface tension, its density, the contact angle between the liquid and the capillary wall, and the radius of the capillary. For example, water, with its high surface tension and strong adhesive forces to glass, exhibits significant capillary action in narrow tubes. Mercury, on the other hand, has weak adhesive forces to glass and strong cohesive forces, causing it to be depressed in a capillary tube rather than rise.

Kapillaariilmiö plays a crucial role in many natural and technological processes. In biology, it is essential for the transport of water and nutrients in plants, from the roots to the leaves, and for the movement of blood in the capillaries of animals. In everyday life, it explains how paper towels absorb spills, how ink spreads on paper, and how oil rises in a lamp wick. Industrially, capillary action is utilized in chromatography for separation processes and in certain types of filters. Understanding kapillaariilmiö is fundamental to explaining a wide range of physical and biological phenomena.