The study of questions has occupied a prominent role in the research into classroom discourse. For science teaching, questions are fundamental since they can connect students with the patterns of scientific thinking. In this article, we developed analytical tools to investigate the epistemic dimension of questions in chemistry teaching. We draw upon Basil Bernstein's concept of classification and the triadic relationship of the knowledge of chemistry to construct the instruments of analysis, and, through their application, we propose to study the distribution of knowledge through questions in classroom discourse. We validated our instruments in a case study of a chemistry teacher who taught in two Brazilian schools, and whose students came from different socioeconomic backgrounds. The results from the analysis indicated differences in the ways in which knowledge is imparted by the teacher in the two classrooms. In the lower socioeconomic context, the approach and posing of questions explored the symbolic form of knowledge more, whereas the approach in questioning to students from the upper socioeconomic context was more related to the theoretical knowledge base of chemistry. These findings suggest that students from lower social strata have access to a simplified chemistry, one that does not necessarily emphasise the theoretical explanations for the scientific phenomena. Considering that the scope of our study is limited to a single case, further research using the proposed analytical instruments in this article is required to confirm these findings.