pinnajännityksen

Pinnajännitys, also known as surface tension, is a property of liquids that causes the surface of the liquid to behave like a stretched elastic membrane. This phenomenon arises from the cohesive forces between 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 more strongly to the molecules below and beside them than to the molecules in the air above. This imbalance of forces pulls the surface molecules inward and sideways, creating a net inward force that minimizes the surface area.

This inward pull is responsible for several observable effects. For instance, small insects like water striders can walk on water because their weight is not enough to break the surface tension. Water droplets tend to form spherical shapes because a sphere has the smallest surface area for a given volume. Pinnajännitys also plays a crucial role in capillary action, where liquids rise in narrow tubes. The adhesion between the liquid molecules and the tube walls, combined with the cohesive forces of the liquid (pinnajännitys), allows the liquid to overcome gravity and move upwards. The strength of pinnajännitys varies depending on the liquid and the surrounding environment, being influenced by factors such as temperature and the presence of dissolved substances.