Exploring the use of context-based green chemistry experiments in understanding the effects of concentration and catalyst on the rate of reaction

Chemistry is acknowledged as a subject that enables students to understand the quality of life. Chemistry forms the basis to understand other sciences including biology, environmental science, physics, and geology. It is known as "central science" (Goldsby & Raymond, 2013). For this reason, children are recommended to be exposed to chemistry from early stage of schooling (Ware, 2001). At the secondary school level, chemistry is perceived difficult because it requires learning concepts which are invisible to human eyes (Taber & Coll, 2002). The abstractness of the concepts demands the use of appropriate teaching strategies to enable students to construct mental images of the concepts. Unfortunately, in doing so, teachers immanently engaged in imparting knowledge on chemistry ignoring the societal consequences of the knowledge. As Hofstein and Yager (1982) once said that contemporary science stresses the advancement of knowledge rather than improving the society.

Green chemistry which reflects on an environmentally responsible way of teaching and learning chemistry when implemented in an educational context, it is well documented that this is a possible mean to educate the students on the knowledge inherent to the environment and society. In the past, green chemistry was used as an approach to contextualizing the learning to the local societies (Eilks & Rauch, 2012). These initiatives resulted in various cognitive and affective outcomes, including, improving understanding of chemistry concepts ( Karpudewan, Ismail & Sinniah, 2016; Parrish, 2007); and environmental attitude and motivation (Karpudewan, Ismail & Roth, 2012; Karpudewan, Roth & Ismail, 2015). In terms of enhancing understanding of concepts, there are still many chemistry concepts left uninvestigated due to its abstract nature and difficulty to employ appropriate pedagogy to teach the concepts including teaching the effects of concentration and catalyst on the reaction rate. Mainly, this happens because the concepts were taught using laboratory activities involving hazardous chemicals and the concept was taught in a way that it is indeed foreign (not relevant) to the students' culture.

The harmful materials used in the reactions made the concepts irrelevant to the students, resulting in the concepts not being further investigated (Eddy, 2000). To address this notion, in this study, students learned the effects of concentration and catalyst on the reaction rate using context-based green chemistry experiments. Context-based green chemistry experiments (CBGCEs) is a new initiative introduced through this study in answering the emerging research question: "does the experimental group students taught using CBGCEs have better understanding on the effects of concentration and presence of a catalyst on rate of reaction compare to the control group students taught using the usual conventional curriculum?"