With support from the NSF Improving Undergraduate STEM Education Program: Education and Human Resources (IUSE: EHR), this project aims to serve the national interest by investigating factors that create effective classroom environments for large undergraduate chemistry courses. To accomplish this goal, the project will gather data from large enrollment courses at the University of Iowa, the University of Arizona, Middle Tennessee State University, and Stonybrook University. It will use these data to determine the features of collaborative activities that foster high-quality student engagement and meaningful learning. Special attention will be paid to the participation of diverse student populations, such as first-generation college students and English-language learners. Core findings from this research project will be used to develop and disseminate faculty resources that will support creation and implementation of effective classroom activities. The research design for this project is based on the understanding that collective activity is a sociological construct that fosters the construction of ideas through different patterns of interaction. Productive ways of reasoning emerge as learners solve problems, explain their thinking, and represent their ideas when engaged in well-designed and relevant tasks that are properly facilitated. Thus, at the center of the research design is the observation, recording, and analysis of student-student as well as student-facilitator conversations to: a) characterize critical characteristics of collaborative task facilitation that most strongly support productive engagement; b) explore how different features of task design (e.g., structure; focus; cognitive demand; opportunities for knowledge integration; co-construction of knowledge) affect students' modes of reasoning and productive engagement in argumentation and explanation; and c) characterize the interaction of task design and facilitation with student discourse in large chemistry classes and determine how those interactions hinder or facilitate the productive engagement of diverse students by reducing barriers to their equal participation in and contribution to group work. The NSF IUSE: EHR Program supports research and development projects to improve the effectiveness of STEM education for all students. This project is in the Development and Implementation Tier, Engaged Student Learning Track. Through the Engaged Student Learning track, the program supports the creation, exploration, and implementation of promising practices and tools. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.