This article reports research from a 3 year digital learning project to unite conceptual change and scientific reasoning in the learning unit of combustion. One group of students had completed the course combining conceptual change and scientific reasoning. The other group of students received conventional instruction. In addition to the quantitative data, six students from each group were interviewed to evaluate their conceptual change, correct concepts and scientific reasoning. Results indicate that the experimental group's students significantly outperformed the conventional group on the Combustion Achievement Test (CAT), Scientific Reasoning Test (SRT) and Combustion Dependent Reasoning Test (CDRT). Moreover, the experimental group's students use higher levels of scientific reasoning more frequently and changed their alternative concepts more successfully than did the conventional group. Furthermore, once the experimental group's students' successfully changed their conceptions, their concepts tended to be more stable than the conventional group's students, even after the 6th week of learning. These results demonstrate that combining conceptual change and scientific reasoning indeed improves students' conceptual change and scientific reasoning ability more effectively than conventional instruction.