<![CDATA[Based on the initial analysis, it was found that the low critical thinking ability of students was caused by the learning which was still centered on the teacher, with the use of learning limited to textbooks. To overcome this, this study aims to improve students' critical thinking ability in science learning, especially the material of changes in the state of matter through the Problem Based Learning (PBL) Learning Model in fourth grade students at SDN Sukoharjo 4. In this study there are two problem formulations, namely (1) How is the application of the Problem Based Learning learning model in the learning of science on the material of changes in the state of matter in class IV of SDN Sukoharjo 4? (2) How is the improvement of the critical thinking skills of class IV students of SDN Sukoharjo 4 in the learning of science on the material of changes in the state of matter before the application of the Problem Based Learning model?. The purpose of this study (1) To determine the application of the Problem Based Learning learning model in the learning of science on the material of changes in the state of matter in class IV of SDN Sukoharjo 4. (2) To determine the critical thinking skills of class IV students of SDN Sukoharjo 4 in the learning of science on the material of changes in the state of matter before the application of the Problem Based Learning learning model. This study uses the Classroom Action Research (CAR) method which is carried out in 2 cycles, where each cycle consists of 2 meetings. The research subjects are class IV students at SDN Sukoharjo 4, totaling 22 students The results of the study showed that there was a significant increase in learning outcomes. Based on the pretest results, the number of students who completed was 3 students (13.63%) and those who had not completed were 19 students (86.36%). In cycle 1 there was an increase with the number of students who achieved completion as many as 10 students (45.45%) while 12 other students (54.54%) who had not completed. Learning if 80% of students get complete learning outcomes. Therefore, learning outcomes at this stage have not met the expected classical completeness standards. Then in cycle II there was a significant increase with the number of students who achieved completeness as many as 19 students (86.36%) while 3 other students (13.63%) who had not completed so that classical completeness was achieved. The results show that the existence of the Problem Based Learning learning model can improve students' critical thinking skills.]]>
