Collaborative problem solving (CPS) can support online learning by enabling interactions for social and cognitive processes. Teachers may not have sufficient knowledge to support such interactions, so support needs to be designed into learning modules for this purpose. This study investigates to what extent an online module for teaching nutrition in secondary school science, using a wiki for CPS, enables interactions, and social and cognitive processes. The module was implemented with 31 volunteer participants. Data collected from the online communications was analyzed for the types of interactions and processes based on the Community of Inquiry Framework. This was triangulated using transcripts of interviews with students. In addition, pretests and posttests were conducted to determine whether the learning outcomes were achieved. Analysis of the online communications showed that the interactions were mainly between learner and content (64.4%), with a large portion of cognitive processes (69.3%) but little social (4.0%), attitudes (9.9%), teaching processes (12.9%) and noise (5.9%). The findings suggest that the module could be used to improve outcomes of learning and encourage interactions for cognitive processes and online presences. The findings may provide insights in encouraging CPS for learning science online.