Surface tension
Liquids tend to adopt shapes that minimize their surface area.
This places the maximum number of molecules in the bulk.
Droplets of liquids tend to be spherical because a sphere is
the shape with the smallest surface-to-volume ratio. The work
needed to change the area by ds is:
The coefficient g is called the surface tension. It has dimensions
of energy per unit area (J/m2). At constant volume and temperature
the work of surface formation is equal to the Helmholtz free energy:
Since dA < 0 is a spontaneous change surfaces tend to contract.