To determine the surface energy released when two identical water drops coalesce to form a larger drop, let's go through the process step by step:

Volume Conservation:

When two droplets, each with a radius R, merge to form a larger droplet, the total volume is conserved. Therefore:

Solving for , the radius of the larger drop, we find:

Initial Surface Energy ( ):

The initial surface energy of the two smaller droplets is given by the surface area of each multiplied by the surface tension T :

Final Surface Energy ( ):
The surface energy of the larger droplet is given by:

Energy Released:
The energy released in the process is the difference between the initial and final surface energy:

This expression gives us the amount of surface energy that is released when two identical water drops combine to form a single larger drop.