Recent national reforms focus on learning disciplinary core ideas through engaging in science and engineering practices. These reforms also call for students and teachers to use crosscutting concepts (CCCs), or analytical lenses, that support scientific sensemaking and connections across disciplines. The "Framework for K-12 Science Education" (National Research Council, 2012) posits that CCCs must be made explicit to provide students with access to scientific sensemaking processes. This study analyzes class dialogue during the implementation of an NGSS-aligned curricular unit that integrates science, engineering, and computational modeling for fifth-grade students. The analysis focuses on the implicit and explicit use of CCCs to support student learning. Findings show that although the CCC of systems and system models was the focus of the unit and professional development, systems appeared in the class dialogue much less frequently than other CCCs, and teachers used all of the CCCs at some point during the unit. With the exception of patterns, all references to CCCs were implicit within the classroom dialogue. This study provides evidence that the CCCs play an important part in classroom conversation that focuses on integrating disciplinary core ideas with science and engineering practices. This work has implications to help teachers, teacher educators, and researchers identify the set(s) of CCCs that may have the most explanatory value for particular DCIs and SEPs, as well as highlights the need for professional learning experiences to promote explicit use of CCCs by teachers and students within classrooms.