When students plan and carry out experiments, they draw on experience and on technical concepts constructed from this experience. This is not only visible in verbal interactions, but also in nonverbal actions, for example in interactions with experimental apparatus. The nonverbal interactions have hardly been the subject of conceptual research so far. The documentary method enables an analysis of multimodal interactions and thus allows insights into subject-specific conceptions and challenges in learning that have not yet been reconstructed on the topic of ‘distilling’. From the available data material (video recordings of chemistry lessons in an eighth grade), a documentary analysis of the students’ interactions with the experimental apparatus and with each other showed that the students drew on subject-specific concepts in different ways during the experiment when interpreting observations and subsequently adapted their actions. Three types of interaction were reconstructed: A) Observations are evaluated as incidental and do not entail interactions. B) Observations are expectant and successful interactions with the apparatus are reinforced. C) Observations are irritating. Discarding previous assumptions or recourse to previously unconsidered experiences follow in discourse. From the interactions, conclusions can be drawn about technically appropriate and inappropriate ideas.

After the analysis, the students’ action-guiding ideas are related to the scientific perspective and the educational structuring of the topic ‘distillation’ in the sense of educational reconstruction, which becomes visible in the teaching setting. Overall, it can be concluded that the distillation of an ethanol-water mixture is not a comprehensible example of substance separation for students at this school level.