The purpose of this study was to interpret students' participation in terms of social and argumentation norms to improve understanding of social interaction in scientific argumentation. Therefore, the study sought to identify social and argumentation norms formed in group argumentation and to explore changes in students' participation as lessons progressed. Twelve lessons that included argumentation were delivered to 44 eighth graders in Korea. In each lesson, small group argumentation tasks were introduced after the teacher had explained the main concepts or after student-centred hands-on activities. We analysed argumentation in one focus group based on various data, including audiotaped and videotaped conversations, field notes and student interviews. In early lessons, discussions were always teacher-initiated and led by a high-achieving student, while other students rarely presented ideas. Moreover, students struggled to seek answers in a textbook and often used analogies and common sense to explain phenomena. They tended to accept others' opinions unquestioningly or ignore other low achievers' ideas in small group argumentation. In later lessons, we observed student-initiated and more equally distributed discussions, in which students were likely to make claims or statements actively based on experimental results and scientific knowledge. Along with these changes in discussion style, some students were seen to support the building of social norms and argumentation norms in a group. Also, performing tasks and receiving guidance from the teacher helped to build students' epistemological norms about scientific argumentation.