An experimental work carried out within the framework of research on the development of devices for teacher training in physics at the National University of General Sarmiento is presented. The device allows the determination of the coefficient of elasticity "K" of a metallic spring when its temperature is modified. The variation of the coefficient has as a direct consequence a variation of the internal energy. It is established, from the theoretical model, the way to calculate it. Finally, the construction of the device used is described and the results obtained are presented.