The purpose of this research is to investigate the effect of the problem-based learning on students' academic achievement
regarding to the concept of enthalpy, which is one of the most important in thermodynamics, and concepts of difficulty in
teaching, and attitudes towards laboratory applications. The subjects were 31 third-year undergraduate students enrolled to a
physical chemistry laboratory-I course in the Department of Chemistry Education in the spring semester of the 2011/12 academic
year at Faculty of Education from a Turkish University. The students in groups of single and dual, every week of ten weeks for
two groups participated of the same experimental study. The enthalpy concept test was administrated at the beginning and the
end of each pre-and post-test experimental study and repeat the test was to determine the level of reliability and durability after
treatment. Statistical analysis of experimental data, paired t-test was applied in the confidence interval of 0.05. At the end of the
application of problem-based teaching model, the students’ academic achievement gap between pre-test scores and post-test
scores was found to be a statistical significant difference