The teaching of chemical equilibrium requires that teachers have a thorough understanding of this concept and they know its use to predict the evolution of chemical systems. Recent studies have shown that even many teachers seem not able to predict the evolution of a system that has undergone a certain type of perturbations. The goal of this book is to "to testify that it is possible - starting by the history of science and difficulties of student's learning – to design, investigate and improve innovative experimental didactic approaches for the teaching of the concept of chemical equilibrium. This is an attempt to show how it is possible to do engineering didactics for the emancipation of the activity of teachers: from simple loudspeakers of the scientific propositions to promoters of scientific knowledge."