Computational science is a field that deals with the construction of computational models. It is characterized by its interdisciplinary nature. Computational science is now being taught in universities and recently even in high-schools. This paper describes research into the learning processes of tenth-grade (16-year-old) students studying a course in computational science. Following an initial finding that students achieved meaningful learning of physics, our primary goal was then to investigate the learning processes that led to this outcome. In particular, we wanted to characterize the contribution of computer science to the students´ learning. We conducted a micro-level analysis of a pair of students engaged in solving a problem in computational physics. The analysis was conducted within the framework of Knowledge Integration proposed by Linn and Eylon [1,2]. We describe the learning processes that the students went through with emphasis on the contribution of computer science to learning physics; this contribution was particularly apparent in developing criteria for evaluating acquired knowledge.