Chemistry is usually seen as a difficult subject for secondary school students. One topic they struggle is when they face chemistry formulation for the first time. The concept of oxidation number is difficult for them. The level of abstraction required is still developing in their minds. We must help them visualise it, to understand bonding and, finally, the symbolic representation of chemical compounds.We find in chemistry a visual description for bond formation: Lewis diagrams. They explicitly show molecular bonds as paired electrons. By using this simple idea, we can introduce formulation to secondary school students. Starting with binary chemical compounds, included in 3rd year of secondary schools in Spain, we can set up the foundations for their future chemistry studies. Of course, the difficulty must be progressively introduced.In this work, we show how a visual method based on Lewis diagrams improves the performance of students when writing formulae of binary chemical compounds. One important difference with current literature on how Lewis dot structures are used in education, is that, while they are usually presented as a learning goal, here we use them as a means to an end.Our results suggest that the improvement is higher for students with previous lower academic performance, low scores in linguistic competencies, and high scores in visual and artistic competencies. Most importantly, it does not worsen performance for students with high scores in linguistic competencies and low scores in visual and artistic competencies. Mathematical competencies do not seem to be so good predictors for students’ performance.Finally, within the Cognitive Load Theory framework, we show how cognitive working load, as well as an approximation of extraneous cognitive load, can be estimated by using information theory measures involving the mistakes students make.
A VISUAL DESCRIPTION OF THE CONCRETE EXTERIOR OF THE CACTUS CRATER CONTAINMENT STRUCTURE
