The societal implications of technology developed through physics are not always clear. Physicists need to use ethical reasoning skills to maneuver through morally ambiguous situations. For this reason, curricula for physics students should also be geared towards developing these skills. This thesis focuses on the effects of ethical discussions in the physics classroom. I present an examination of physics students' engagement in a unit about the development of the atomic bomb through a two-part study where students interpret and apply an ethical framework to discussions about the development of the atomic bomb and current STEM research. Using both student written work and video-recordings of in-class discussions, I analyze how the curriculum design may influence student learning. Study 1 uses students' written work to understand how they interpret and apply an ethical framework to their discussions about the development of the atomic bomb and to current STEM research. Our analysis shows that students conflate certain ethical principles and/or avoid their negative implications, which in turn leads to a misapplication of the principles. However, students also demonstrate a range of productive approaches to applying these ethical principles which contribute to the development of strong ethical arguments. Study 2 uses video-recorded data of classroom interactions to understand how ethical discussions can be supported in the classroom. Our analysis shows the emergence of different group dynamics that seem to fall along a spectrum of engagement modes. The emergent modes are defined by the extent to which students share a collective sense of what is going on in their group and build on each other's' ideas. From the analysis, I consider how cues from the professor and LAs, as well as the availability of guiding prompts and other relevant curricular resources, influence these dynamics. I also share possible implications of these findings for instruction physics education researchers