Rigorous Evidence and Reasoning or Not? A Demonstration of Iron Corrosion to Induce Students’ Critical Thinking

Evidence-based reasoning and critical thinking are two crucial scientific abilities of students, sharing a close relationship with each other—critical thinking is not just randomly refuting but a logical-reasoning thinking based on solid evidence. However, in real teaching circumstances of experiment classes, students easily directly accept the conclusions they have been given, without critical thinking and full comprehension of the relationship between experimental evidence and the resulting conclusions. In this work, a demonstration experiment of iron corrosion was developed. More than teaching the knowledge of specific chemical reactions in the case, the experiment was designed for the further purpose of stimulating students' critical thinking. During implementation, instead of showing the well-designed experiment scheme directly, the teacher first showed the preliminary outline and then revealed the process of revising the outline gradually to become the final rigorous scheme. In each step, students were asked to seek evidence and flaws in the reasoning process that appeared in the experiment, as the basis for subsequent revisions. After three revisions, teachers and students agreed that the evidence and reasoning process of the scheme were sufficiently rigorous. The performance of the students during the class showed that the students' attitude toward the demonstration experiment has changed from passive acceptance to active reflection and questioning. The feedback from students after class showed that students' awareness of evidence-based reasoning and critical thinking has been enhanced.