This study aimed to develop the small-scale experiments involving electrochemistry and the galvanic cell model kit featuring the sub-microscopic level. The small-scale experiments in conjunction with the model kit were implemented based on the 5E inquiry learning approach to enhance students' conceptual understanding of electrochemistry. The research tools consisted of (1) four small-scale experiments involving electrochemistry, which were oxidation and reduction reactions, galvanic cells, cathodic protection of iron nails, and connecting batteries in series, and (2) the galvanic cell model kit with the ability to generate various galvanic cells. The data collecting tools included (1) a conceptual test of electrochemistry and (2) the mental model drawing of a galvanic cell. Thirty-four grade 12 students participated in the series of four 5E learning activities for a total of 10 hours. Paired samplesT-test analysis revealed that the mean scores of the post-conceptual test (mean 36.63, SD 7.69) was statistically higher than that of the pre-conceptual test (mean 21.51, SD 6.83) at the significance level of 0.05. In addition, the mean scores of the post-mental models in both the macroscopic (mean 3.56, SD 1.30) and sub-microscopic features (mean 5.98, SD 2.93) were statistically higher than those of the pre-mental models (mean 1.85, SD 1.11 and mean 2.20, SD 2.45) at the significance level of 0.05. Prior to intervention, most students were in the categories of less correct conceptions, Partial Understanding with Specific Misunderstanding (PMU) to No Understanding (NU). However, after the intervention, they moved to the categories of more correct conceptions, Partial Understanding (PU) to Sound Understanding (SU). This indicated that this intervention can enhance students' conceptual understanding of electrochemistry and mental models of galvanic cells.

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The main purpose of this study was to enhance student understanding of the scientific concepts of chemical reaction rate. Forty-four grade 11 students were the target group. The treatment tools were seven learning plans of 5E inquiry incorporated with an analogy learning approach during 15 hours of class time. In each learning plan, the students (1) addressed a scientific question regarding chemical reaction rate, (2) explored evidence to answer the question by carrying out a corresponding experiment,(3) drew explanations from collected evidence to answer the question, (4) elaborated their understanding by studying the given analogy and the target, and (5) evaluated their conceptual understandings by creating their own analogy and identifying similarities and differences of their analogies and the targets.The data collecting tool was a conceptual test of chemical reaction rate, consisting of 30 two-tier three-choice questions. The normalized learning gain for the whole conceptual test was at the medium gain level (0.64). The dependent samples t-test analysis indicated that the post-conceptual test score (mean 45.32, SD 6.46) was statistically higher than the pre-test score (mean 19.70, SD 3.10), but was statistically lower than the retention test score (mean 48.03, SD 9.04) at the significance level of 0.05.In the pre-conceptual test, the percentages of students in the good-, alternative-, and misconception categories were 13.69, 38.45, and 47.86, respectively. In the post-conceptual test, the percentages of students in these categories were 64.72, 24.6, and 10.63, respectively. This finding indicates that this implementation was an effective means to enhance and retain students' conceptual understanding of chemical reaction rate.

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The present work describes a simple hands-on experiment kit for colorimetric quantification of ferric (III) ion (Fe 3+ ) in an aqueous medium using anthocyanin extracted from Ruellia tuberosa L. as a green indicator. The extraction of a high amount of anthocyanin was easily accomplished by using only hot water instead of an organic solvent. The formation of the colored Fe 3+ −anthocyanin complex occurred on a homemade 24-well plate and the generated color was captured by a smartphone. The increase in color intensity was measured in the red, green, blue (RGB) system by the ImageJ software under the optimum conditions. The developed method enabled quantification of Fe 3+ at low concentrations with the detection limit of 0.03 mg L −1 and provided the linear range (0.05−2.0 mg L −1 ) with good linearity (R 2 = 0.9985) with Fe 3+ concentration. The concentrations of Fe 3+ in water samples determined by the developed method were not significantly different from those measured with UV−visible spectrophotometry at a 95% confidence level. In addition, the extracted anthocyanin stored at 4 °C was stable for two months. This hands-on experiment was implemented as a 2 h activity for 30 grade-12 students in which they were asked to determine the concentration of Fe 3+ in a water sample using the smartphone-assisted colorimetric method. The students' understanding of the related concepts of oxidation−reduction and determination of iron was collected by a diagnostic conceptual test. Having participated in the experiment, the students were found to have significantly improved understanding of both concepts.