In the present paper, we describe and discuss an approach to the teaching of the conceptually demanding topic of fluids which focuses on promoting student teachers' conceptual evolution towards a suggested scientific model. We discuss a comprehensive conceptual model about fluids to be taught to primary education student teachers based on the interrelation of content analysis and students' domain specific conceptions and reasoning. We also present features of a relevant instructional strategy, involving conflict and enhancement procedures, as well as of the experimental field linked to the conceptual model to be taught. This teaching sequence was applied to a small sample of student teachers aiming at the in-depth description of their conceptual development. Comparison of the intended sequence with student teachers' actual constructions in the course of teaching revealed unexpected intermediate steps in their evolution towards differentiation of the intensive variable pressure and the extensive variable force.