This study aims to determine the effect of the REACT learning model on students' mastery of cognitive concepts in the material of temperature and heat at SMA Muhammadiyah Makarti Jaya and to find out whether there is a significant effect of the REACT model on students' mastery of concepts. This study uses a quasi-experimental research type with a Nequivalent Control Group Design. The total population in this study is all class XI IPA SMA Muhammadiyah Makarti Jaya. Then the sample used in this study was 1 class with 2 groups, namely the experimental class and the control class each with 16 students and the sampling technique used Non probably sampling with Purposive Sampling where the sample was selected by means of certain considerations. Based on the results of the independent samples t-test test output, a significance value of 0.000