Studies indicate that qualitative understanding of phenomena, as expressed in students explanations and predictions, is not satisfactorily achieved by most high schools and college graduate students. Even after instruction of basic domains such as introductory mechanics, students conceptual understanding of topics remains almost unchanged. We argue that it can be done by unpacking the difficulties that are faced in this domain and by developing a method that responds to these problems discussed above. More specifically, we suggest that it is advisable to choose tasks that focus on ...