This research is conducted to know the effectiveness of the guided inquiry model integrated with STEM to enhance the student critical thinking skills. This reseach is begun with development of chemistry learning device for thermochemistry topic using the 4-D model. The subject of reseach are the fifty seven students of XI grade divided in two classes (MIA- 1 and MIA-2) at Muhamadiyah 10 Senior High School, Surabaya, Indonesia. The results of study showed that validity of the learning device developed were very valid category. The guided inquiry model integrated with STEM was effective to increase the student critical thinking skills with gain score of medium category for the MIA-1 class and high category for MIA-2 class, respectively. There was significant difference between pretest score and post test score for two classes based on t-test analysis. The critical thinking skills of students changed from very less critical category to critical category, in both classes studied.

Keywords : Guided Inquiry, STEM, Critical Thinking Skills, Thermochemistry.