Unit of Surface Tension

Defining Surface Tension

Surface tension is an interesting topic to study. It is defined as the attractive force that is found mostly in liquids which pulls molecules in the surface together, resulting in the minimization of the surface area. In more technical terms, surface tension is the energy required to increase the surface area of a liquid by a unit of area. The surface tension is present due to the imbalance of inter-molecular attractive forces or the cohesive forces between molecules. This phenomenon mostly occurs with water, but it can happen with other liquids as well. Surface tension is represented by the symbol γ (alternatively σ or T) and is measured in force per unit length. However, here we will look at some units of surface tension.

SI Unit of Surface Tension

The SI unit of surface tension is a Newton per meter or N/m.

Other Common Surface Tension Units

The CGS unit of surface tension is dyne per centimetre. It can be represented as;

It can also be measured as surface energy using J/m2 or ergs per square centimetre.

Witnessing Surface Tension in Daily Life

We find various examples of surface tension in nature, and we have listed a few of them below:

  • Small insects such as water striders walk on water because their weight is not enough to penetrate the surface.
  • A small needle when carefully placed over the water surface can be made to float on water though the needle is several times denser than water. If the surface is agitated to break the surface tension, then the needle disturbs the surface tension and will quickly sink.
  • Soaps and detergents lower the surface tension of water so that it can more readily soak into pores and soiled areas.
  • Water droplets acquire its round shape due to surface tension. They are pulled spherical shape by cohesive forces of the surface layer

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