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Paper short abstract:

In natural science lessons substances are omnipresent. Chemicals and everyday substances take part in 'experiments'. My paper explores two ways of representation: firstly, in form of practical experimentation and secondly in form of the chemical notation on the blackboard.

Paper long abstract:

Chemical substances are ubiquitous in natural science lessons and entwined in laboratory practice. So far the use of substances has not been examined in detail. Therefore, the aim of my paper is to discuss, how the use of substances can theoretically and empirically concep-tualised using natural science lessons as an empirical case.

My paper explores the following two aspects in more detail: the ontological one in the context of school experimentation, the formal one by the writing on the blackboard using chemical symbols. The direct manipulation of the chemicals must be learned and a sense for their ap-propriate handling must be developed. Chemicals become relevant through their sensual perception and can communicate information through chemical reactions, for example a change in colour or smell. Based on this chemicals become also relevant in their sensual perception. Hence, substances can be used through their representations. Secondly, chemi-cal reactions produce visual indicators which have to be observed, articulated and re-presented in 'chemical writing'. I am going to explore how students are trained to transform the bodily perceived reactions of substances into characters i.e., the chemical equation.

The participation of students in the practical management and manipulation of (dangerous) chemicals, their semiotic representation and their discursive embedment produce knowledge through the material entanglement. The presented empirical data derive from participant ob-servations of school lessons and guided experimentations in a university student lab.