This research investigated how student social interactions within two approaches to an inquiry-based science curriculum could be related to student motivation and achievement outcomes. This qualitative case study consisted of two cases, Off-Campus and On-Campus, and used ethnographic techniques of participant observation. Research participants included eight eighth grade girls, aged 13-14 years old. Data sources included formal and informal participant interviews, participant journal reflections, curriculum artifacts including quizzes, worksheets, and student-generated research posters, digital video and audio recordings, photographs, and researcher field notes. Data were transcribed verbatim and coded, then collapsed into emergent themes using NVIVO 9. The results of this research illustrate how setting conditions that promote focused concentration and communicative interactions can be positively related to student motivation and achievement outcomes in inquiry-based science. Participants in the Off-Campus case experienced more frequent states of focused concentration and out performed their peers in the On-Campus case on 46% of classroom assignments. Off-Campus participants also designed and implemented a more cognitively complex research project, provided more in-depth analyses of their research results, and expanded their perceptions of what it means to act like a scientist to a greater extent than participants in the On-Campus case. These results can be understood in relation to Flow Theory. Student interactions that promoted the criteria necessary for initiating flow, which included having clearly defined goals, receiving immediate feedback, and maintaining a balance between challenges and skills, fostered enhanced student motivation and achievement outcomes. Implications for science teaching and future research include shifting the current focus in inquiry-based science from a continuum that progresses from teacher-directed to open inquiry experiences to a continuum that also deliberately includes and promotes the necessary criteria for establishing flow. Attending to Flow Theory and incorporating student experiences with flow into inquiry-based science lessons will enhance student motivation and achievement outcomes in science and bolster the success of inquiry-based science.