I am not a novice at thermodynamics but still the following question made me think over my status more than twice. I have to find the equilibrium temperature when a 50 Kg block of copper at 80C is placed in a container which as 120L of water at 25C. I made simple equations of heat lost = heat gained. Used Specific Heat for water = 4.18 and for copper 0.285 (and 0.391) and used mcdelT. But the answer I get is below 25C. Where as it should be between 25 and 80.