In order to use and understand a scientific language students need the ability to move between everyday and scientific discourses. This article analyses exploratory talks, and use of language when students collaboratively discuss a science assignment. The aim is to develop an analytical tool that can facilitate understanding and visualization of students' language use. The concepts of discursive mobility (Nygård Larsson, 2011) and semantic waves (Martin, 2013; Maton, 2013) constitute the starting point in the analysis and the students’ discussions are explored by using the concepts of semantic gravity and semantic density. The results display that all of the students’ conversations contain a certain degree of discursive mobility. However, there exists differences in how the conversations move between everyday and scientific languages and in terms of how successful the students are to formulate a specific subject language. In some conversations, everyday expressions become a productive resource and a bridge to a more scientific language.