The purpose of this study is to investigate the effects of the cooperative learning approach based on conceptual change conditions over traditional instruction on 10th grade students' conceptual understanding and achievement of computational problems related to chemical equilibrium concepts. The subjects of this study consisted of 87 tenth grade students from two intact classes of a Chemistry Course instructed by the same teacher. One of the classes was randomly assigned as the experimental group, which was instructed with cooperative learning approach based on conceptual change conditions and the other class was assigned as the control group, which was instructed with traditional instruction. Chemical Equilibrium Concept Test (CECT) was administered to the experimental and the control groups as pre- and post-tests to measure the students' conceptual understanding, and Chemical Equilibrium Achievement Test (CEAT) was administered to the experimental and the control groups as a post-test to measure the students' achievements related to computational problems. Science Process Skills Test was used at the beginning of the study to determine the students' science process skills. Multivariate Analysis of Covariate (MANCOVA) was used to analyze the data. The results showed that students in the experimental group had better conceptual understanding, and achievement of computational problems related to the chemical equilibrium concepts. Furthermore, students' science process skills were accounted for a significant portion of variations in conceptual understanding and achievements related to the computational problems.