This study analyses the evolution of school-level scientific models proposed by prospective pre-primary teachers (PPTs) (a) about the water molecule and its intermolecular bonds, and (b) representing the different states of water molecule aggregation at a microscopic level. The data were acquired from the PPTs' responses at the beginning and at the end of the intervention to two open-ended questions. Given the qualitative and interpretive nature of the study, the responses were analysed and categorised by combining inter- and intra-rater evaluation methods. In general, positive evolution was observed in the models for both questions, progressing from representations that were symbolic, macroscopic, or without differentiating the constituents of the molecule to molecular representations that were more coherent. They ended up presenting a more proportionate ratio between the sizes of the two types of atom involved, considering the approximate angle between the bonds, and even differentiating the intra- from the intermolecular hydrogen bonds characteristic of water to describe the states of water molecule aggregation. The conclusion was that, with interventions of this kind, it is possible to initiate PPTs in the practice of scientific modelling as part of their training as science teachers at the initial levels of education.