`1000` small water drops, each of radius `r`, combine and form a big drop. In this process, find decrease in surface energy.

Explanation

Suppose radius of big drop is `R`. During this process, mass will be conserved, so volume will also be conserved.
`("Volume")_("initial") = ("Volume")_("final")`
`((4)/(3)pir^(3)) xx 1000 = ((4)/(3)piR^(3)) rArr R = 10r`
loss in surface energy
`DeltaU_("loss") = TDeltaA_("loss") = T((4pir^(2)) xx 1000 - 4pi(10r)^(2))`
`DeltaU_("loss") = (T)(900 xx 4pir^(2))`
this energy loss will be converted into heat. So increase in temperature of the drop can be found from `T(900 xx 4pir^(2)) = msDeltaT`, From this get the incerase in temperature `DeltaT`.