Abstract : Our work intends to use the visit of a factory so that the students work out an empiric referent for the starting of the learning of chemical thermodynamics. Leaning on the modelization diagram by J.-L. Martinand (1995), the work includes the analysis of the working of the factory to build up modelizing elaborations accessible to the students, from the speech delivered by a technician in charge of the maintenance and the technical documents put at our disposai. In parallel with the analysis of these data, one test of a teaching sequence including a visit gave information about what students identify, about the questions they ask themselves, the ones in which they advance, about the links they try to set up with their theorical knowings. The articulation of those two points allows to work out activities which will be suggested to the students. This is a work based on the empiric referent in its différent shapes : objects, phenomenons, phenomenography, phenomenotechnics, phenomenology.