Ragionamenti fondamentali nel calcolo stechiometrico: superare le difficoltà con la densità

The ability to solve problems in science subjects is an essential component of student’s education. Solving complex problems is a real difficulty for many students. This study, which extends for decades and involves students from different high schools, has been developed with the aim of finding strategies to increase students’ skills in the chemical problems where density is one of the data in the text. Using the results of various studies to the full, various strategies have been suggested and implemented. A consistent improvement of the results in the written examination tasks was obtained with the use of the ‘worked examples’ method. This method has been developed within the Cognitive Load Theory. A ‘worked example’ provides students with useful information on a solved problem: not only it shows the sequence of steps, but it comments them, illustrates, and explains them by motivating, and arguing them.