Theorical framework and research questions

This contribution explores the potential of the carbon cycle for teaching an environmental issue through chemistry lessons at the lower secondary school.
Environmental issues are complex by essence. Morin (1990) uses the Latin etymology of the word “complex”: complexus, “weaving together”, as a metaphor to illustrate the very close relationship between academic subjects in a complex approach: as each coloured thread is important to build the pattern of a fabric, we need to cross different subjects’ approaches to understand environmental issues challenges and to be able to solve them (Morin, 1990, p. 21). As an example, the carbon dioxide produced by human activities – modelized as a chemical reaction in chemistry - must be connected to the greenhouse effect model to deal with the complexity of the Anthropocene. According to Mohan et al. (2009) and Zangori et al. (2017), the carbon cycle seems to be a good entry into the Anthropocene’s complexity. Mohan et al. (2009) shows how the principle of conservation of matter is important for analyzing the carbon cycle, especially to understand natural and human carbon dioxide productions. In their study, Zangori et al. (2017) try to connect the carbon cycle, the chemical reaction, and an environmental issue: the global warming. Results from their experiment show an improvement of the learning of the principle of conservation.
In French-speaking countries, the curriculum is organised into school disciplines, taught during distinctive time slots by specialised teachers at secondary level. Such an organisation questions the teachability of topics such as environmental issues and sustainable development. Martinand (2016) suggests that it requires many adjustments between school disciplines with specifics traditions, epistemologies, methodologies, and sometimes different purposes. However, the implementation of these adjustments in teaching and learning practices brings out new questions for didactic research.
In France and Western Switzerland, curricula texts at lower secondary level show some tensions between two purposes of sciences curricula: educate citizens on the one hand and teach specific scientific concepts on the other hand (Auteure1 et al., accepted). Moreover, these tensions are also reflected in the different purposes assigned to the school disciplines at lower secondary school. Whereas chemistry education seems oriented towards the teaching of specifics concepts and models (e.g., atoms, molecules, chemical equations), environmental issues tend to be taught in biology and geology only. However, chemistry is involved in environmental issues. Firstly, because it is historically connected with the industry (Bensaude-Vincent and Stengers, 2001), chemical products can potentially impact the environment. Secondly, because chemistry develops a range of models useful to analyse and understand environmental issues. Hence, chemistry as a school discipline has a role to play in understanding environmental issues (Martinand, 2016), but this role remains to be defined.
According to Chevallard (2004), the “co-disciplinary approach to a problem” (p. 8, our translation) consists in the balanced collaboration of the academic disciplines involved, oriented towards a shared goal: finding an answer. The carbon cycle is a common model in biology and geology: its structure in circle allows to connect human activities and their environmental consequences. From a chemical point of view, each arrow on the cycle could be modelized as a chemical reaction (photosynthesis, respiration, combustion, etc.) From our perspective, integration of the carbon cycle in a chemistry teaching could create the conditions for a co-disciplinarity approach. Thus, the following research questions are pursued: is the implementation of a co-disciplinarity approach possible in order to connect the chemical transformation and the global warming by using the carbon cycle? Which indications of this co-disciplinarity could be found in the teaching practices?

Methodology Four chemistry teachers participated to the study (two in each French-speaking context: Montpellier area in France, Geneva district in Western-Switzerland). The data were collected for two consecutive years. The first year, we video-recorded the “ordinary” teaching practices (Author2, 2023). The second year we suggested to the teachers to integrate the carbon cycle into their teaching of the chemical reaction. The resulting teaching was also video-recorded. Semi-directive interviews with the teachers and a few numbers of their students were conducted before (teachers) and after (teachers and students) each recording period. All these video data were transcribed. In order to construct indications of co-disciplinarity in classroom interactions we draw on an epistemological analysis of knowledge involved: the chemical reaction (Kermen, 2018), the carbon cycle model (Orange et Orange, 1995; Labbe Espéret, 2002) and the global warming (Mohan et al., 2009; Zangori et al., 2017).

Expected Outcomes From our perspective, a co-disciplinary approach seems to be the condition to study a complex question in science classroom such as the Anthropocene. Therefore, we aim to create this condition by implementing an environmental issue – the global warming, based on the carbon cycle - in chemistry lessons. We expect to observe how chemistry’s specifics concepts – chemical reaction and the principle of conservation of the matter – deepen the understanding of global warming. This connection should involve an explicit relation between the models from different school subjects. Furthermore, some specificities of the educational systems of the different countries could facilitate or imped the take-off of a co-disciplinarity approach in chemistry teaching. For example, Western-Swiss teachers use the same official textbooks in their daily practices, which makes it a very strong guiding tool for teachers’ practice. In France, teachers are free to choose any teaching aid. Therefore, they might feel freer to implement new ways of teaching chemistry.

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