LAUSR

The paper presents a study in which 54 university students were introduced to a newly developed, free, web-based 3DChemMol molecular editor with a toolbar, which they then evaluated. The tool aims to increase representational competence related to submicroscopic representations. Students who used the software for the first time, were instructed to create molecular models using the model building/editing tools in three activities with varying levels of difficulty: 1) building a simple model (butanoic acid), 2) converting one model (hexane) into two models, 3) converting from a non-cyclic to a cyclic structure (glucose). It took students from two up to 15 minutes to accomplish each of the activities. Several types of help were available in the 3DChemMol molecular editor toolbar to assist students during their activities, including a video tutorial, button hovering, action status display, and a help menu. Undo/redo and restart options were also available. Students' completion level, difficulties, and use of the help features were investigated using student self-evaluation questionnaires. The 3DChemMol molecular editor proved to be a useful support for students in completing simple chemistry activities. Students were successful in model building, although they encountered some specific difficulties, especially in steps that involved spatial operations, such as rotating the selected part of molecule around the bond. In students' perception, the video tutorials were the preferred and most frequently used type of help, and the undo function was considered essential. The results suggest that the 3DChemMol molecular editor can be used effectively in introductory chemistry courses at the tertiary level, whether for direct instruction, self-study, or other forms of support in the pedagogical process. The results and new findings of this study will be used to further optimize the interface in future versions of the evaluated tool.