The objective of this study is to identify the difficulties encountered by Moroccan high school students concerning the modeling of chemical reactions, microscopic and macroscopic concepts. The symbolic register of the balanced equation represents a chemical reaction; its reading can be done at a macroscopic level and/or at a microscopic level. The originality of our study consists in suggesting, for the first time, a progression between microscopic and macroscopic phenomena. This study allowed us to face the fact that both learners and new teachers have great difficulty in understanding the basic concepts related to chemical reactions and basic redox concepts. It became clear to us that it is necessary to conduct a thorough and integrated study of the elements involved in the educational process: curriculum - official instructions - professional experience of the teachers in order to know the deficiencies and therefore to seek ways of regularization and remediation.