Surface tension? How does it work?

Surface tension refers to the amount of energy required to increase the surface of a liquid per unit area, this energy is needed since liquids exert resistance when increasing the surface. So we can understand surface tension as a kind of elastic membrane that makes it difficult to enter the liquid. This means, for example, that some insects such as the shoemaker can land on river water.

The superficial tension arises from the forces that act cohesively the molecules of the liquids. These forces are not equal on the surface and inside the liquid, although on average they end up canceling out. Since the surface molecules have more energy, the system tends to minimize the total energy from a reduction of the surface molecules; in this way, the area of ​​the liquid is reduced to a minimum.

One of the properties of surface tension indicates that as the liquid has higher cohesive forces, it will have a higher surface tension. In any case, it must be taken into account that the surface tension is linked to the temperature, the medium and the nature of the liquid.

There are various measurements of what the surface tension of a liquid is. However, one of the most widespread and used is known as the Du Nouy method, which is undertaken using two important tools such as a sheet of the liquid in question and an aluminum ring. Starting from these elements, the calculation is carried out taking into account parameters such as the force or the diameter of the aforementioned ring.

To gain a little more insight into the function of surface tension, let’s perform the following experiment and get to work!