The societal implications of technology developed through physics are not alwaysclear. Physicists need to use ethical reasoning skills to maneuver through morallyambiguous situations. For this reason, curricula for physics students should also begeared towards developing these skills. This thesis focuses on the effects of ethicaldiscussions 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-partstudy where students interpret and apply an ethical framework to discussions aboutthe development of the atomic bomb and current STEM research. Using both studentwritten work and video-recordings of in-class discussions, I analyze how thecurriculum design may influence student learning. Study 1 uses students' written workto understand how they interpret and apply an ethical framework to their discussionsabout the development of the atomic bomb and to current STEM research. Ouranalysis shows that students conflate certain ethical principles and/or avoid theirnegative implications, which in turn leads to a misapplication of the principles.However, students also demonstrate a range of productive approaches to applyingthese ethical principles which contribute to the development of strong ethicalarguments. Study 2 uses video-recorded data of classroom interactions to understandhow ethical discussions can be supported in the classroom. Our analysis shows theemergence of different group dynamics that seem to fall along a spectrum ofengagement modes. The emergent modes are defined by the extent to whichstudents share a collective sense of what is going on in their group and build on eachother's' ideas. From the analysis, I consider how cues from the professor and LAs, aswell as the availability of guiding prompts and other relevant curricular resources, influence these dynamics. I also share possible implications of these findings forinstruction physics education researchers