The purpose of the paper is twofold: (1) To contrast the longstanding tradition of private and public courses of chemistry with the public demonstrations of physics. Whether taught in public institutions such as the Jardin du Roi or by apothecaries in their officines chemistry demonstrations were not for the entertainment of their audiences. Rather, they were intended to train people in pharmacy and natural philosophy. (2) By the end of the eighteenth-century, however, pneumatic chemistry prompted a new style of presentation and experimentation more similar to experimental physics, as shown by the famous experiment of water decomposition and recomposition performed by Lavoisier in 1785.