a piece of copper at 120 degrees celsius has exactly twice the mass of another piece of copper at 40 degrees celsius. The two pieces are brought together and allowed to reach equilibrium. What is the final temperature.

Answer 1

heat lost by 120 C Cu + heat gained by 40 C Cu = 0
I would choose some convenient number like 10 g for one of the pieces and 20 g for the other; substitute into the
[mass x specific heat x (Tfinal-Tinitial)] + [mass x specific heat x (Tfinal-Tinitial)] = 0
Solve for Tfinal.
I obtained an answer approximately 90 C.