Searching for solutions

Students’ understanding of solutions can be somewhat shallow, even at advanced levels of study, and this has been the subject of a great deal of research in recent years. Kevin de Berg has carried out an investigation to probe how well students in their first year at tertiary level understand the concept of solution concentration, leading to interesting outcomes.

The introduction provides a useful synopsis of previous research in this area, highlighting the challenges faced by students in rationalising the macroscopic phenomenon of solution formation (eg what they see when sugar dissolves in water) and the submicroscopic representations (SMR) used in teaching. Other studies cited identified the difficulties associated with unifying verbal reasoning with visual representation, an issue also encountered in this study.

The diagnostic test was made up of multiple choice questions featuring SMR along with short answer questions presented in verbal form. The author highlights some of the problems inherent in particle diagrams, which will be of interest to teachers at secondary level who use them routinely. These include the issue of increased cognitive load arising from the addition of extra details, and the lack of scale integrity resulting from the inclusion of macroscopic features such as a container outline or a horizontal solution surface.

Interestingly, students fared better on verbal questions than on those which featured SMR tasks. In particular, a number of students failed to account for volume changes in questions based on SMR, instead focusing only on the number of particles. It is notable that some of the students interviewed suggested that ‘verbal questions were easier to interpret’, but there was universal agreement that the use of both question-types provided reinforcement of the concept. In conclusion, it is suggested that educators should continue to increase exposure of students to visual representations, but they must also build links to verbal modes to facilitate the development of deeper understanding.