In this study, we examine a socio-scientific issue associated with a modelling activity for secondary pre-service science teachers and investigate how the modelling activity promotes the teachers' argumentative practice around the given socio-scientific issue, specifically dam removal. This study utilizes a qualitative research method grounded in a constructivist epistemology (Merriam, 1998). Twenty pre-service science teachers participated in the study and the participants' SSI debate discussions, before and after a physical model activity, were used as a main data source. The results show that the experience of manipulating variables in a physical model helped the pre-service science teachers improve the content and quality of argumentative practice by allowing them to manipulate variables, apply prior knowledge, and develop analogies to compare the model with the real situation.