Designing problems and learning activities is a key factor to initiating students’ engagement with the course material and influencing their reasoning processes. Although tasks and problems are a central part of teaching and assessments in the chemistry classroom, they may not engage students in deep reasoning or in a way that is intended through a task. Some problems may cause an algorithmic or a surface approach. Even with designing clever problems, students may not use a larger variety of chemistry ideas and connect them in meaningful ways. Here the idea of scaffolding students’ answering process comes into play. Structuring students’ reasoning process through instructional prompts or structured worksheets supports students in activating and connecting knowledge pieces in a more meaningful way and positively slows down their fast decision-making process. This paper will discuss the importance of asking questions in chemistry teaching and highlights the idea of contrasting cases, drawn from cognitive psychology, as a task design principle. In addition to having contrasting cases as a good problem format, the idea of scaffolding students’ reasoning while solving contrasting cases through the use of instructional prompts that scaffold the reasoning process will be exemplarily showcased for mechanistic reasoning in organic chemistry.