Design activities are increasingly used in science, technology, engineering and mathematics (STEM) education. Guiding students during these activities can be challenging for STEM teachers, who may be inexperienced in the field of design. In this study, we focused on a case of three chemistry teachers who implemented design projects in their classrooms. During the lessons, the students designed a self-heating or self-cooling cup, in which the energy effect of chemical reactions causes a heating or cooling effect on the cup's contents. Through an in-depth analysis of the conversations between the teachers and student groups, we aim to understand how teachers verbally support students and any factors that may influence this. We used concepts from scaffolding theory to analyze the support. By organizing the data into segments based on these scaffolding concepts, we were able to characterize the different approaches taken by the teachers. The types of support varied; for example, the teacher might take control of the process or stimulate the students' reasoning. The support appears to be adapted to the students, the lessons and the topics of the conversations. These are possible factors that may influence the way in which teachers support the students during design activities.