The current research aimed to develop Depth of Scientific Knowledge Levels and Mental Motivation among primary school pupils, by using REAPS model in teaching (Natural Resources on the Earth's Surface unit) in science for fifth grade primary school pupils in the second semester of the academic year 2023-2024. Considering this, a research sample consisting of (70) male and female pupils was selected, from Al-Hurriya Primary School affiliated to West Zagazig Education Administration. The research tools were represented in (depth of scientific knowledge test and mental motivation scale). The research relied on the quasi-experimental design with two groups, where the research tools were applied to them before, then the unit was taught to them. After completion, the research tools were applied after, and the results indicated that the performance of the experimental group pupils in the post-application was superior to their performance in the pre-application and to the performance of the control group pupils with a statistically significant difference at the level (0.01) in terms of developing depth of scientific knowledge levels and mental motivation among them, the results also showed the effectiveness of teaching the unit using REAPS model in developing depth of scientific knowledge levels and mental motivation among the experimental group pupils. The research presented a set of educational recommendations and research proposals in light of the results that were reached.