In this research; aim was determining student achievement by comparing problem-based learning method with teacher-centered traditional method of teaching 10th grade chemistry lesson mixtures topic. Pretest-posttest control group research design is implemented. Research sample includes; two classes of (total of 48 students) an Anatolian High School student in 2014-2015 academic year. Treatment took place for 16 hours. Experiment group treated with problem-based learning method, control group was treated with teacher-centered traditional method. Data was conducted with scientific achievement scale and t-test was used to analyse data. Findings showed that there was a significant difference between two groups in favour of students treated with problem-based teaching in terms of scientific achievements in mixtures topic.