The study intended to investigate the effectiveness of problem based learning (PBL) on the cognitive development of class IX students’ in the subject of chemistry. The objectives of the study were to; examine the effect of problem based learning on academic achievement of the students in chemistry, examine the effect of problem based learning on academic achievement of the students with different level of achievements, determine the effect of problem based learning on cognitive domain of secondary school chemistry students and to determine the effect of problem based learning on cognitive domain of secondary school chemistry students with different level of achievements. The sample consisted of class IX students of Working Folks Grammar Higher Secondary School No. 1, Haripur. Pre-test, post-test equivalent group design was used for this study. On the basis of pre-test results, students were divided into two groups and named randomly as experimental and controlled group having 45 students in each group. The same test was also given to experimental and controlled groups as a post-test to compare the effects of teaching chemistry through problem solving method and traditional method on students‟ achievements. Before the application of PBL, 5 groups were made in which there were 9 students in each group. The study recommended that the teacher should be encouraged to employ problem based learning in teaching chemistry and it should be incorporated as an essential part in training for science teacher by introducing different courses in order to implement it.
Keywords: Problem Based Learning, Cognitive Domain, Chemistry, Academic achievement