An exploratory study was to determine the effectiveness of discussion sessions as a teaching strategy of thermodynamics in basic physical chemistry of fundamental concepts in this area as spontaneity by explaining students according to their ideas. A previously validated questionnaire was used as an instrument on thermochemistry, enthalpies of bonding, and Gibbs function. The performance of the students who participated in the intervention was compared with that of a control group to which the afore mentioned teaching strategy was not applied. The students of the intervened group explained with a higher academic level the concept of spontaneity than those of the control group reaching the level of the development of the process of effective chemical reasoning (DECRP) of the taxonomy of barrow and bloom.