Surface tension is a physical property of the surface of a liquid that makes it behave like a stretched elastic membrane. It arises because the molecules at the surface of a liquid experience a stronger attraction to each other (cohesion) than to the molecules in the surrounding air or other phases. This imbalance causes the liquid surface to contract and resist external forces, effectively minimizing its surface area
. More specifically:
- Surface tension is the force exerted along a line of unit length on the surface of a liquid, measured in newtons per meter (N/m), or equivalently, the energy required to increase the surface area of the liquid, measured in joules per square meter (J/m²)
- It is responsible for phenomena such as the spherical shape of small liquid droplets, the ability of some insects (like water striders) to walk on water, and objects denser than water (like razor blades) being temporarily supported on the water surface without sinking immediately
- Water has a relatively high surface tension (~72.8 mN/m at 20 °C) due to strong hydrogen bonding between its molecules, compared to many other liquids
- Surface tension decreases with increasing temperature because molecular attraction weakens
- It plays an important role in processes like wetting, capillarity, droplet formation, and dispersibility of particles in liquids
In essence, surface tension is the liquid's tendency to minimize its surface area by contracting, behaving as if its surface were covered by a stretched elastic film
