The aim of the study is investigating the effect of constructivist approach on students' understanding of the concepts related to hydrolysis subject, comparing constructivist approach with traditional teaching method and determining the differences between student success in constructivist approach and traditional teaching method. Totally 100 students have participated in the study. The age average of the students is 18-21. The control and the treatment group have been determined randomly. Traditional teaching applications have been conducted with control group and constructivist teaching applications have been conducted with treatment group. Hydrolysis Concept Test has been administered as pre test to control and treatment groups to determine the understanding level of the students related to hydrolyzes concepts. The data has been analyzed by using statistical analysis techniques. The results have displayed that the constructivist teaching applications has had contributions on students' understanding of the concepts related to the hydrolysis subject. (C) 2011 Published by Elsevier Ltd. Open access under CC BY-NC-ND license.