Pedagogical approaches to surface phenomena in liquids: Investigation-based laboratory and modelling activities to improve students’ learning

Paperclips can float on water, mercury drops do not spread on solid surfaces, and fluids can flow against gravity in capillary tubes. Surface tension can be used to explain these phenomena that are macroscopic manifestations of microscopic molecular interactions. At both school and university levels, surface phenomena are introduced through traditional macroscopic or microscopic approaches. However, since explanations based on microscopic models are often in conflict with common macroscopic interpretations, the traditional teaching of the basic concepts related to surface phenomena can be unclear and can prevent students from an effective understanding of the topic. However, since surface phenomena applications are important in physics and other applied disciplines, it may be worth to reconstruct this content based on research results in Physics Education. Research demonstrates that models constructed at an intermediate scale (i.e., mesoscopic scale) can be used effectively in science education. Particularly, the literature recognizes mesoscopic models as valuable for efficiently introducing topics such as solid friction and fluid statics. These models have the benefits of the microscopic model. Particularly, they foster understanding based on the recognition of a “mechanism of functioning”, that is at the basis of the development of explicative lines or reasoning. Furthermore, these models do not require a significant amount of computer resources to execute simulations implementing the models. On the basis of these observations, we asked ourselves how we could contribute to improve the teaching and learning of this topic. We hypothesised that choosing an appropriate modelling scale to introduce a given topic would appreciably enhance the teaching/learning processes at both school and university levels. On the basis of our research hypothesis, we decided to study how and to what extent different didactical approaches based on macroscopic and mesoscopic description, respectively, can foster the teaching and learning of surface phenomena at secondary school level. We designed two teaching-learning sequences (TLSs), one based on macroscopic modelling, and the other on mesoscopic modelling, which were trialled each with a group of upper secondary school students. Each TLS was based on an inquiry-based approach and was planned to involve students in active learning practices. The main goal of the trialling was not to identify which group highlights the best learning depending on the different modelling approach, but to verify the aspects of each approach that can be considered truly relevant in promoting learning. The planning and implementation of the two TLSs were guided by the general research question “which aspects of each approach can be considered relevant in promoting students’ scientific learning?”. The data collected during the trialling of the TLSs (student worksheets, interviews, students’ answers to questionnaires etc.) were studied by means of qualitative and/or quantitative analysis methodologies. Resuming some results, after the instruction students who followed the macroscopic approach, appear more capable than students who followed the mesoscopic approach, in describing complex phenomena involving liquid-solid interaction, as capillarity. However, a close analysis of their answers to questionnaires, shows that they acquired a quite superficial knowledge, as they simply memorized notions and information on the topic, but did not reach a proper awareness of it. On the other hand, after the instruction students who followed the mesoscopic approach seem more capable of building explanation than students who followed the macroscopic approach. We can infer that mesoscopic modelling activities can support the development of explanation-oriented reasoning lines more than macroscopic traditional ones. We found that students who followed the mesoscopic approach understood more deeply than students who followed the macroscopic approach the analysed topics. This, however, often happens with respect to simple physical situations like the ones involving liquid-liquid interactions. These students found it difficult to understand more complex physical situations as those involved in liquid-solid interactions. In general, both groups show comparable levels of well-being in learning. This indicates that the inquiry-type approach proposed through the two TLSs has been welcomed by most of students. The mesoscopic approach promoted the development of the willingness to extend studies and research more than the macroscopic approach and this led students to reinforce beliefs and acquire behaviours characteristic of a growth mindset. On the other hand, students who followed the macroscopic approach developed the ability of generalization of what has been learned more than students who followed the mesoscopic approach.