Unknown and variable: the semiotic potential of a digital balance-model.

The aim of this paper is to analyse a specific digital environment designed to introduce equations. More specifically, through the instruments provided by the Theory of Semiotic Mediation, I study the semiotic potential of an artifact constituted of two balances, one fixed and the other movable, to mediate the mathematical meanings of unknown and variable. Having conducted preexperimentation, I present some excerpts to highlight artifact-signs emerging during the activities that, with appropriate intervention of an expert, could evolve into mathematical signs. An excerpt from an artifact-integrated activity with a low-achieving student is analysed in more detail to show the complexity of the relation between artifact signs and mathematical signs.