Q12.59P - Chemistry: Molecular Nature Of Matter And Change

Question

Why are units of energy per area $(\mathbf{J}\mathbf{/}{\mathbf{m}}^2)$  used for surface tension values?

 

Step-by-Step Solution

Answer

Surface tension is the force experienced by the surface molecules of the liquid. The quantity is dependent on the number of molecules present on the surface; thus, the units of surface tension is $(\mathbf{N}\mathbf{/}{\mathbf{m}}^{-1})$  i.e., Force per unit meter or energy  $\left({\mathbf{Fm}}^{-1}\right)$ per unit area.

Step 1: Surface Tension

The surface tension is the force experienced by the liquid surface molecules because of the unbalanced forces of attraction on the surface.

 

Step 2: Unit of Surface Tension

As the surface tension is the force experienced by the molecules, its unit should be Newton /meter. In other words, as Energy is the force applied per unit meter, the surface tension is the energy per unit square meter i.e., $(\mathbf{J}\mathbf{/}{\mathbf{m}}^2)$ .