The course of thermodynamics is one of the subjects whose material content consists of real theory and practice and the use of formulas. Therefore, in the application of this course is a need to apply a learning model that is able to help students find and solve problems and be able to explain their findings in achieving the basic competencies of thermodynamics course. The learning model is a Problem Based Instruction learning model based on Blended Learning. This study aims to improve the critical thinking skills of pre-service physics teacher as a result of using Problem Based Instruction based on Blended Learning in the course of thermodynamics. Retrieval of data in this study was conducted on third semester students of physics education study programs that take Thermodynamics course. This research was conducted in September-October 2019. The research method used is quasi-experimental. Quasi-experiments are research carried out on a single group of students. Data analysis in this study used a one-party t-test. The results showed that (1) the application of the Problem Based Instruction learning model based on Blended Learning can improve students’ critical thinking skills, (2) Students’ responses to the application of the Problem Based Instruction learning model based on Blended Learning get a very happy category of ongoing learning.

Students were intellectuals who should have the ability to think critically, one of which is the creative thinking skills. However, the students' limited ability in basic physics as well as the limitations of using a variety of multimedia resulted in basic physics final exam results lower than 6 on average from maximum value of 10. This leads to the lower creative thinking skills of students in basic physics. This research is a Quasi Experiment research on students in the first semester of academic year 2014/2015 which amounted to 38 people. This research is expected to increase creative thinking skills as well as lecturers and students activities. Data obtained from this study is the data of creative thinking skills of students and data on the observation of activity of lecturers and students. The data were analysed by using formula percentage of completeness of learning outcomes, gain indexes and statistical t-test. Based on the results of data analysis it is showed that the use of interactive multimedia (Macromedia Flash) can improve creative thinking skills of students.