In this work, we developed an ontological tool, based on the scientific realism of Mario Bunge, for the analysis of the presentation of natural processes in science textbooks. This tool was applied to analyze the presentation of the concept of osmosis in 16 chemistry and biology books at different educational levels. The results showed that more than 50% of the books present the process of osmosis connected just with concentration properties associated with the hydrodynamic state of the osmotic process, forgetting the properties of osmotic pressure to define the state of osmotic equilibrium. This omission creates confusion between the state of osmotic equilibrium with the isotonic state by reducing the entire osmosis process to a mere process of diffusion by differences in concentrations. Moreover, in 4 of the biology textbooks, the presentation of the osmosis concept and osmotic equilibrium in cell system illustrations generates confusion between hydrostatic pressure generated by gravity vs. hydrostatic pressure generated by membrane tension or turgor pressure. Our results show that in most of the texts, the osmotic process is not connected with the non-equilibrium state, macroscopic dynamic state or equilibrium state, whereas in other textbooks, equivalence between these states and hypo-hyper and isotonic states is incorrectly presented.