1. The problem statement, all variables and given/known data In a copper calorimeter of mass m=100g, there is water of mass m1=200g with a temperature of t1=4°C. A copper body of mass m2=300g and temperature t2= - 20°C is inserted into the calorimeter. a) What will be the final temperature inside the calorimeter? b) Show that one fraction of water would turn into ice if the inserted copper body were to have a temperature of t2= - 50 °C. Calculate the mass of the formed ice. 2. Relevant equations Q=mcΔt and second law of thermodynamics 3. The attempt at a solution To solve a) I wrote the equations for the heat that will leave the water+copper calorimeter system and for the heat that the inserted copper body will receive. Then I set them equal and found for what temperature are those two quantities the same (t=1,2°C). That is correct. For b) I don't have an idea how to solve it since I don't know how can I check whether there will be a phase transition of water during the process, and whether all water will turn into ice or just a portion. I don't either quite understand the solution of a), since I apply equations for calculating heat without phase transitions etc., but don't quite know how can I prove that there won't be a phase transition. Shouldn't that be the first step of the solution, and only then applying equation? Also, I tried working with maximum heat that water can give to copper, but the problem is that I don't have any lower or upper value of temperature so I could calculate the maximum heat.