In this study, we examine how bilingual students in elementary school use their languages and what this means for their meaning-making in science. The class was multilingual with students bilingual in different minority languages and the teacher monolingual in Swedish. The analysis is based on a pragmatic approach and the theory of translanguaging. The science content was electricity, and the teaching involved class instruction and hands-on activities in small groups. The findings of the study are divided into two categories, students' conversations with the teacher and student's conversations with each other. Since the class was multilingual, the class instruction was carried out in Swedish. Generally, when the conversations were characterised by an initiation, response and evaluation pattern, the students made meaning of the activities without any language limitations. However, when the students, during whole class instruction, were engaged in conversations where they had to argue, discuss and explain their ideas, their language repertoire in Swedish limited their possibilities to express themselves. During hands-on activities, students with the same minority language worked together and used both of their languages as resources. In some situations, the activities proceeded without any visible language limitations. In other situations, students' language repertoire limited their possibilities to make meaning of the activities despite being able to use both their languages. What the results mean for designing and conducting science lessons in a multilingual class is discussed.