Many research results show that students often highlight “mixed-type” reasoning when tackling problematic situations and problems. This reasoning is based on the simultaneous use of common-sense and mere descriptions of facts, perceived as sufficient to build an “explanation” of observed or proposed situations and problems. This fact can be interpreted as a lack of coherence. In this paper, we study the coherence of responses that a sample of undergraduate chemical engineering student give when they are asked to face real-life situations, to create explanations, and to use models in different contexts. We administered open-ended questionnaires before and after a twenty-hour Inquiry-Based workshop related to phenomena activated by a thermal overcoming of a potential barrier. Based on the Physics Education Research literature on student understanding of relevant physics contents, the student responses are analysed by using researcher-generated categories of reasoning and their coherence is studied. Finally, we discuss some implications of the results to improve the development of students’ explicative skills.