The elaboration of the salt hydrolysis concept by cooperative learning

Abstract

In this paper the elaboration of the concept of salt hydrolysis by cooperative studying with the first grade Gymnasia students (general secondary school; science – mathematics orientation; aged 15) is presented. Eight different experimental tasks had been prepared (for eight groups of students) the results of which, in combination with the previously acquired theoretical knowledge (Bronsted – Lowry theory), had been expected to enable students to form and internalize their own notions of salt hydrolysis. By comparing the acid – base properties of the aqueous solutions of the given salts (the selection of which had been made according to specific criteria), as well as the properties of their constituent cations and anions, the students were able to deduce which protolytic reactions take place in aqueous solutions of salts. Upon the completion of the experimental phase, and through extensive discussions on the results obtained by all the groups (a considerably larger number of examples than that which is usually used at the elaboration stage), the students were able to draw general conclusions on the properties of aqueous solutions of different salts. The effects of this approach were tested by a parallel-group pedagogic experiment. The approach was the most successful at the understanding level (61% of correct answers more in the experimental group than in the control group), as well as at the level of the active use of theoretical knowledge in explaining changes perceived in experiments (23% of correct answers more in the experimental group than in the control group).