Question

if steam & water each at 100c are taken as two systems and made to be in contact with each other, does the heat flow takes place or not? if heat flows my question is "how can heat flow without temp diff in contrast to the conventional definition?" if it doesn't, how can these systems attain equilibrium?

Answer 1

Heat energy will only if there is temperature difference between two system. Objects at the same temperature are said to be in thermal equilibrium (no heat flow). Heat leaving from one object will be gained by the same amount from the other object so the net flow of heat is equal to 0.