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Asia-Pacific Forum on Science Learning and Teaching, Volume 19, Issue 2, Article 3 (Dec., 2018) |
Chemical kinetic involves learning rate of chemical reaction and factors affecting the rate such as concentration, catalyst, size, temperature and pressure, which is very much difficult for the students at the secondary level to comprehend (Kirik & Boz, 2012). Except for non-zero order reaction, concentration is one of the factors that alter the reaction rate whereby an increase in the concentration accelerates the reaction (Turanyi & Toth, 2013). Due to this reason, the concentration of a solution, and its importance has attract the attention of many researchers in eliciting students' understanding (Yalçinkaya et al., 2012).
The effects of concentration are investigated in multiple ways. In Thailand, traditionally reactions between calcium carbonate and hydrochloric acid with different concentration (Chairam et al., 2009) was used to teach about effects of concentration. In Malaysia, collision theory was used to explain the effect of concentration followed by investigating the reaction between sodium thiosulphate solution with various concentrations and sulfuric acid (Curriculum Development Centre, 2006). This traditional way of teaching resulted in the students retaining misconceptions about the influence of concentration (Cakmakci, 2010). Reacting sodium thiosulphate solution and sulfuric acid resulted in the students investigating the reaction and behaviors of the particles at the molecular or submicroscopic level. Learning and understanding the reactions of both substances ends at the molecular level. Misconceptions occur during translation of molecular level knowledge to the concrete, real-life phenomena at the macroscopic level. Teaching using a context-based approach permits expansion of investigation from viewing the behaviors at the molecular to the application into real-life situations.
Another factor that can alter the reaction rate in any chemical reaction is the presence of catalysts. Catalysts are needed to initiate a specific chemical reaction, and it is widely used in industries (Kingir & Geban, 2012). For the students to have an in-depth understanding of the reaction, understanding the role of catalyst in chemical reactions is required. In learning about catalysts, students need to understand the activation energy of the reaction. As mentioned by Tastan, Yalcinkaya, and Boz (2010) any increase or decrease in the activation energy of the reaction depends on the catalyst used. A Swedish chemist, Jöns Jacob for the first time coined the word "catalyst" in 1835 and asserted that catalyst is a substance that increases the rate of a reaction without changing the chemical properties of the substance itself. Catalyst exists as a positive and negative catalyst. A positive catalyst increases the rate of a reaction by lowering the activation energy of the reaction using an alternative path for the reaction to occur while negative catalyst decreases the rate of reaction by increasing the activation energy using an alternative path during the reaction (Haber, 1994). Sima (2015) claimed students developed misconceptions about the properties and functions of the catalyst during teaching and learning process. It was identified that students tend to perceive positive catalyst reduces the activation energy. But in presences of positive catalyst, the reaction is executed in an alternative route with lower activation energy. Similar to the investigation on the effect of concentration on the rate of reaction, students engaged in investigating the effects of the catalyst at the molecular level. Lacking ability to directly connect the molecular level understanding to real-world phenomena prompted the students in developing misconceptions.
Due to the lacking of ability to connect molecular level understanding to macro-level events, misconceptions retained despite teachers embarked in using various initiatives such as using inquiry/analogy (Suparson & Promarak, 2015); laboratory method (Demircioglu et al., 2011); cooperative learning (Kirik & Boz (2012); and 5E-based animation aided instruction model (Kolomuc, 2009). For instance, i n a study involving, Year 12 students, Karpudewan et al., (2015) deliberately reported that students' conceptual understanding on the effects of the catalyst is more on average level in the first measurement and reported to be lower than average in the second measurement.
Green Chemistry and Context-Based Green Chemistry Experiments
Green chemistry which is also known as sustainable chemistry, when the 12 principles of the green chemistry were infused into educational context is a form of chemistry that focuses on the environmentally responsible way of teaching and learning (Anastas &Warner, 1998). The lessons on green chemistry deal with less or no hazardous materials to humans and the environment compared to the traditional polluting chemistry (Hjeresen, Schutt & Boese, 2000). During green chemistry lessons life-cycle analysis of a product was performed (Juntunen & Aksela, 2013, 2014) and discussion on alternative fuels and bioplastics were executed (Mamlok-Naaman et al., 2015). Green chemistry was used to address sustainability in classroom practices (Burmeister et al., 2012). Green chemistry principles have been integrated into specific cases (Kennedy, 2016) as classroom activities (Parrish, 2014; Prescott, 2013) and as laboratory experiments (Purcell et al., 2016). In some instances, green chemistry also implemented as laboratory-based pedagogy (Author et al., 2012). In the examples above lessons solely on green chemistry have been executed. On the contrary, this study explains how context inherent to the effects of concentration and catalyst on the rate of reaction is integrated into green chemistry experiments and presented as CBGCEs.
According to Seery (2015) application of the knowledge could be executed through context-based learning. In the context-based learning platform students are presented with relevant everyday context that emanates from the chemistry content that they are learning. CBGCEs introduced through this study is a kind of context-based learning pedagogy. The learning is contextualized using appropriate examples. For instance, learning about the presence of a catalyst in a reaction was contextualized using rising of the cake or bread when yeast is used as a catalyst. To identify the effects of concentration students recognizes that the taste of orange juice is different when water is added to the orange juice. Alternatively, students were shown bleach (Clorox) functions more effectively in the pure form compare to the diluted form.
Learning based on an issue requires students to understand the issue and to solve the issues using the knowledge that has been taught (Joel, Kamji & Godiya, 2016). Joel et al., (2016) had conducted a study with 100 students on understanding the rate of chemical reaction. A quasi-experiment design was used, and students in both groups were given worksheets, in which they needed to discuss the rate of reaction and explain the rate and reaction using daily life examples. The performance of experimental group student noted to be way better. This probably because the experimental group students' learning was extended to a context where the students had to understand the application of the knowledge. In a different study, Nieswandt, (2001) claimed that learning and understanding chemistry would be much easier when it is related to daily life activities. Nieswandt (2001) had conducted a study with 9th-grade German students who were taught chemistry using everyday life activities. The study was based on two basic chemistry concepts: changes of substances and particles model of matter. The analysis done at six different times showed that students had a better understanding of the chemistry concept when they were taught using daily life activities.
Activity theory is a framework used to discover the complexity of real-world situations in learning, and it is a tool used to understand learning (Engeström, 1987). Particularly, activity theory is instrumental in understanding the connectivity between tacit knowledge and scientific approach (Vygotsky, 1978). CBGCEs implemented is this study could be fundamentally explained using activity theory. To facilitate the implementation, activity theory is presented as consist of six elements: instrument/tool, subject, object, rules, community, and division of labors (Engeström, 1987). During the activity (the basic unit of analysis) the subject (the learner) together with the community (other students and teacher) performed the action assigned to them (a division of labor) adhering to the rules (procedures of the experiments) in achieving the objectives. These objectives are later translated as the outcome of the activity.
