According to the Kinetic Theory of Matter, temperature is nothing but a measure of the kinetic energy of matter. My textbook says that the change in internal energy of a system is the heat gained plus the work done on it. The heat change, apparantly, is measured using the change in temperature in a calorimeter, using the ideas of specific heat capacity.
Let's say a piston is kept inside a calorimeter, and it undergoes a reaction in which volume is increased. Work is done on the molecules of water in the calorimeter, and radiation is emitted in the course of the reaction. Both the radiation and the work increase the KE of the water, and therefore contribute to the temperature change. So what part of this change is due to work, and what is due to "heat"? How exactly are they differentiated?