The general objective of this thesis was to implement an equipment for the study of the first law of thermodynamics in closed systems, which consists of a three-layer cylinder, an electric resistance, an electric motor with agitator, a temperature controller, and two digital multimeters. The first law of thermodynamics was applied to deduce a model that allows evaluating the variation of internal energy of a liquid, which is related to the voltage and current of the electric resistance, the power of the electric motor, and the heat flow lost by the liquid. The samples used were 5.778 kg of papaya nectar and 5.806 kg of water. The heating of the papaya nectar lasted 660 s, and the variation of internal energy when applying the equations of Choi and Okos and the proposed model was 1.07717 ×106 J and 1.07048 ×106 J, respectively. The heating of water lasted 780 s, and the variation of int...