Two water droplets coalesce to form a large drop. In this process,

When a big drop breaks up into smaller drops, the total surface area of the smaller drops is more that the surface area of the big drop. The increase in the surface area can be brought about by supplying energy. Thus a big drop has to absorb energy to break up into smaller drops. On the other hand, when smaller drops coalesce to form a big drop, there is a decrease in the surface area. Hence energy is liberated in this process.