Communication of scientific knowledge is ultimately multimodal. In science education, many researchers demonstrated that design of science texts has a great role in meaning-making of communicated scientific knowledge. In order to present message, representations are essential elements that need to be designed consciously by science educators. This study investigates meaning-making practices of pre-service science teachers during learning activities. In a social semiotic approach, multimodality principles were executed to reveal how participants think about meaning-making practices, how they design their learn materials, and how they orchestrate during teaching. 41 preservice science teachers participated to study. 33 of them responded multimodal literacy scale, all of them prepared a PowerPointTM presentation as ten groups to teach a certain general chemistry topic and classroom observations were done. It was seen that, in theory almost all pre-service science teachers have representational competence but the results stemming from real practices showed inverse. Results of this study demonstrated that there is a big gap between pedagogical concerns and meaning-making facilities in the practices of pre-service science teachers during a science instruction. It was implied that, designing learning materials that contain high meaning-making potentials and mastering to communicate it requires a theoretical and pedagogical knowledge.