How Studying Greenhouse Effect and Global Warming can Help Understanding Energy

A considerable amount of educational research has been devoted to the teaching and learning of energy concepts and phenomena. Many studies have pointed out students’ common conceptions that can create learning difficulties, and different approaches for teaching energy are designed and experimented. Our experience led us to the conviction that it is necessary to overcome a too de-contextualized and technical approach to physics teaching. In particular, as far as energy issues are concerned, it is necessary to immerse physics contents into the context of scientific culture, by discussing different interpretations which caused historical debates and by considering current issues particularly challenging for students. This means to integrate the Science Technology Society Environment (STSE) approach with the conceptual and procedural dimensions of science learning. We propose to select specific driving issues which can promote the progressive construction of physics concepts and models while highlighting their scope and value and the connection to students’ cultural context. In this perspective we have developed a teaching learning path, devoted to high school students, around the problem of understanding the greenhouse effect and global warming. We wanted to strictly connect the environmental aspects and the scientific content, and we paid particular attention to the conceptual progression and connections with basic energy concepts: differentiating the concepts of work, heat, internal energy, temperature; considering the role of radiation in thermal phenomena; understanding energy conservation and energy balances in stationary situations of thermal non-equilibrium. Our approach includes outdoor activities, reflection in the classroom, and experimental work in the laboratory. Based on preliminary research with small groups of students, we defined a sequence of six cognitive steps toward the construction of a coherent explanation of the greenhouse effect. The teaching path was experimented in six high school classes, for a total of 121 students. We investigated two research questions: - How can the study of a complex issue such as greenhouse effect and global warming improve understanding of energy concepts? - What type of materials, experiments, models and schematic representations can favor students’ understanding of this topic? The results confirm the importance of passing through all the six considered cognitive steps: the greenhouse effect is a complex phenomenon and needs a progressive rapprochement. The analysis of the pre- and post- tests showed clearly an increase in the consideration of the role of radiation in thermal processes, the awareness of energy balance in stationary situations, and a more correct and complex explanation of the greenhouse effect. However many explanations still revealed some imprecision and the idea of “trapping” of sun rays was still used as the easiest explanation of the greenhouse effect. Then a process of refinement of the original teaching sequence was developed leading to the production of new materials for students and a teacher guide, which give more attention and a different way to the introduction of some basic energy concepts. Testing of the refined teaching sequence is now in progress in ten high school classes and new results will be presented at the conference.