surface tension

Surface tension is a fascinating phenomenon that many of us can observe in everyday life, whether in the form of a drop of water attached to a leaf or in the form of insects that can walk on the surface of water. But what exactly is surface tension and why is it so important?

Surface tension is a material property that is used to characterize liquids. It is caused by the attractive forces between the molecules of a liquid. These forces ensure that the liquid strives to keep its surface area as small as possible. Therefore, water droplets can stick to surfaces and insects, such as water striders, can walk on water without sinking.

An interesting example of surface tension is mercury. It has a high surface tension of 484 mN/m. This means that mercury tends to form spherical shapes when placed on a surface. This high surface tension also allowed mercury to be used in ancient thermometers because it could easily rise in narrow tubes.

Oils, on the other hand, generally have a lower surface tension, around 30 mN/m. This means that oils tend to spread more easily across surfaces and do not form spherical shapes as easily as mercury. This is why oil is often used as a lubricant, as it can easily spread between machine parts.

Another common example is distilled water. It has a surface tension of 72 mN/m. This makes water an ideal solvent for many substances.