Question

it is easier to obtain equivalent temperature by adding cold water hot water then doing it the opposite way ?

Answer 1

the cold water is denser than hot water. If you pour it in hot water, the hot water, being lighter, will start moving up and cold water, being heavier will move down. This brings greater mixing.

While on the other hand, if you pour the hot water over cold water, and if you have poured it slowly, then heat transfer will take place gradually from the interface where both meet and eventually equilibrium will be attained. There is relatively much lesser molecular motion and mixing.

HOPE THIS WILL HELP YOU

THANKS