I've got a problem: A piece of copper with mass m1 = 800 g and temperature t1 = 80 ° C is placed in a container with good thermal insulation. The vessel initially contains water with mass m2 = 500 g temperature t2 = 20 C. What is the calorimeter (including thermo meter) heat capacity if the end temperature is tf = 26 C?! The solution is: the specific heat capasity for copper: 0:39 kJ / kg.C and for water: 18.4 kJ / kg.C dQ copper = m1 * CCU * (t1-t0) = 16.85 kJ dQ water = m2* CH20 * (t0-t1) = 12:54 kJ According to the first law of thermodynamics, the amount of heat transferred to the calorimeter and thermometer: dQ = dQ copper - dQ water = 4.31 kJ But how can I find the heat capacity of the calorimeter? I see a solution that I should do this: 4.31 kJ / (26-20) C but why water in this case?! should I always find the specific heat capacity of the calorimeter or the thermometer with respect to the minimum tempraturen?!