This study aims to explore students' conceptual understanding of thermodynamic in ADI for STEM education. The study uses embedded experimental design methods. It involved 29 students of XI grade high school in Kupang. Instruments tes consisted of 13 reasoning multiple chooise questions. Wilcoxon test results is P=.000 with an average posttest higher than pretest shows that there is significant difference between students' conceptual understanding of before and after learning. The effect size value is 2,39. Students' conceptual understanding of each indicator is also discussed.