Background: Research on chemistry education has found that students have commonly some difficulties in understanding chemical changes. These difficulties in the learning process have negatively affected students' success. For this reason, it is very important to overcome students' learning difficulties with new materials that prevent the occurrence of misconceptions and effective learning methods. Purpose: This study aimed to compare the effectiveness of the learning method and the learning material in high-school students' achievements in chemical changes. Sample: The population of the study consisted of 92 students from three-ninth grade high-school classes in Izmir, Türkiye (N[subscript Group-I] = 30, N[subscript Group-II] = 30 and N[subscript Group-III] = 32). Design and methods: The present study in which a pretest-posttest quasi-experimental design was used, was conducted with three groups. Group-I learned via the jigsaw technique using newly developed learning material. Group-II learned via the same technique using the current chemistry syllabus. Group-III learned by using the current chemistry syllabus in a teacher-centred environment. The effectiveness of the learning material was determined by comparing Group-I and Group-II, the effectiveness of the jigsaw technique of cooperative learning used by comparing Group-II and Group-III, and the effectiveness of both learning method and learning material was determined by comparing Group-I and Group-III. After the experiment process, a concept test was administered to identify students' understanding of chemical changes. To determine the students' misconceptions and their views about the learning method, semi-structured interviews were also conducted. Results: The results of the concept test indicated that the mean score of Group-II was significantly higher than that of Group-III, and the mean score of Group-I was significantly higher than that of Group-II. Conclusion: The results of this study showed that the learning material played a greater role than the learning method in achievement and the prevention of misconceptions regarding chemical changes.