The amount of substance and the mole: a historical approach to their teaching and learning

A new didactic strategy is proposed to teach the base quantity amount of substance and its unit, the mole. The concept of relative atomic weight represents the key for counting elementary chemical species by weighing. According to this view it is suggested that Cannizzaro’s approach based on Avogadro’s hypothesis and the “law of atoms” should be one of the best way to teach the mole concept. A table entitled Advances in the atomic-molecular theory is also presented to help the students to understand the mole concept in a historical perspective.