Solution chemistry plays an important role in students' understanding of other related abstract chemistry topics such as acids and bases and chemical equilibrium. From this, it was aimed to investigate whether the laboratory activities based on the 5E model of the constructivist approach has a significant effect on academic achievement of 9th grade students. The present study was conducted with a total of 52 9th grade students in a high school located in the province of Trabzon. While 26 of them were randomly assigned to the experimental group, the other was assigned as the control group (26). The same teacher taught both groups. The experimental group students were taught with laboratory activities based on the 5E model of the constructivist approach whereas the students in the control group were taught with the traditional approach. The laboratory activities based on the 5E model were performed during two lesson periods (45-min per lesson). A Chemistry Achievement Test (CAT) consisting of 11 open-ended questions was developed by the authors. It was applied to both groups. The validity of the CAT was examined by a commission involving 3 academicians and 2 chemistry teachers. The data obtained from pre-and post-tests of both groups was compared with the independent t-test. The results from pre-tests showed that there was no significant difference between control group and experimental group. On the other hand, the post-test results showed that there was a significant difference between groups in favor of the experimental group. It is essential that teachers should develop their skills for designing a constructivist-learning environment within class and laboratory activities. With this aim, teachers should be given in-service training. (C) 2013 The Authors. Published by Elsevier Ltd.