A thermometer is inserted in a small hole in the foil. The body of the calorimeter should insulate the interior from the surroundings. The sum of all energy changes inside the calorimeter must therefore add up to zero. The thermometer measures the change in temperature that results from energy transfers inside the calorimeter. In this experiment, the calorimeter is filled with water at room temperature.
Ice is added.
As the ice melts, it absorbs heat. Since this heat must come from inside the calorimeter, it is extracted from the thermal energy of the liquid water. There are three energy terms involved. Together they should add up to zero . The energy D h fus required to melt the ice.