• Journal of the Korean Chemical Society
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• v.52 no.3
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• pp.303-314
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• 2008

The purpose of this study was to understand the experiment for measuring chemical reaction rate by precipitate formation and to develop experiments applying small-scale chemistry. For this study, the experimental method for measuring the effect of concentration and temperature on chemical reaction rates presented in the 10 high school science textbooks were classified by their experimental methods of confirming production. Subsequently, problems observed in carrying out the experiments for measuring chemical reaction rates by precipitate formation frequently presented in the 10 high school science textbooks were analyzed. Experiments applying small-scale chemistry were developed measuring chemical reaction rate by precipitate formation. According to the result of this study, there were some problems in the experimental method of precipitate formation for measuring chemical reaction rates presented in the high school science textbooks. Those problems in the science textbook experiments were insufficient specification of mixing methods of reaction solutions, obscurity of knowing when the character letter X disappeared, time delay in collecting the experimental data, formation of hazardous sulfur dioxide, uneasiness of fixing water bath container, controlling the reaction temperature, and low reproducibility. Those problems were solved by developing experiments applying smallscale chemistry. Presenting the procedure of mixing reaction solutions on the A4 reaction paper sheet made the experimental procedure clearly, using well plates and stem pipette shortened the reaction time and made it possible to continuously collect the experimental data. Furthermore, the quantity of hazardous sulfur dioxide was reduced 1/7 times and the time when the character letter X disappeared could be observed clearly. Since experiments for measuring the effect of concentration and temperature on chemical reaction rates could be performed in 30 minutes, the developing experiments applying SSC would help students understand the scientific concepts on the effect of concentration and temperature on chemical reaction rates with enough time for experimental data analysis and discussion.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.580-589
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• 2014

The concepts used to explain specific phenomenon can be influenced by context or coherent regardless of context. The purpose of this study is to understand middle school students' concept of particles in particular context and to investigate the effects of context on concept of particles. A conceptual questionnaire was developed to find out how students represented particles in two contexts: solid and solution states of electrolytes, and ion precipitation reaction. The questionnaire was administered to $9^{th}$ grade students after classes of 'electrolyte and ions' unit. The responses of students were analyzed using framework developed for categorization of students' concepts. The results are as follows: First, it was found that students used various concepts on particles when they explained solid and solution state of electrolytes, respectively. Second, we identified students' concepts of particles used to explain ion precipitation reaction. In addition, we recognized that majority of students failed to write correct chemical symbols. Third, approximately 79% of students showed coherent responses for explanation of particles in solution state of both electrolytes and ion precipitation reaction. About 57% of students had scientific concepts. Some suggestions were made based on results for acquisition of scientific concepts on particles in different contexts.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.338-349
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• 2010

This study compared the instruction effectiveness between experiments of precipitation and a ball & stick model related to the 'Law of Definite Proportions' of 9th grade science in this study. The subjects were 250 students in the 9th grade. They were divided into two groups, an experimental group and a model group. The results showed that the ratio of thought in which the elements were divided in the solutions and the ratio of thought in which a new compound was created when the two solutions were mixed were higher in the precipitation experiment group than in the model group. The two groups were not different in terms of the ratio of thought related to the reason for the creation of the precipitate. The ratio of thought pertaining to incorrect answers was high, implying that the two strategies were not effective in correcting students' thoughts. However, the ratio of finding patterns from the measuring data in the model group was higher than in the experimental group. However, the ratios of 'definite proportions' inference in the bonding of the reactants were similar in the two groups. From these data, we concluded that the inference of the 'Law of definite proportion' from experiments or models was not suitable for middle school students.

• Journal of the Korean Chemical Society
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• v.50 no.5
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• pp.374-384
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• 2006

this study, the teaching methods of three science teachers for lead-iodide precipitation reaction experiment were compared. The difference of 9th grade students' understanding was searched according to the science teachers teaching styles, also. Among the three teachers, Teacher A taught students based on the science textbook and allowed students to think themselves and to get out conclusion by the experiment. Teacher B and Teacher C gave students a lot of explanations related to interpretation of the experiment. The percentage of no response on the experiment report of Teacher A was higher than those of Teacher B and Teacher C. But the students of Teacher B and Teacher C tended to have limited thoughts because of the teachers explanations. In spite of the difference, it was common phenomenon that few students understood concepts through the experiment. A lot of students were interested in the experiment, but it was hard to understand Law of definite proportions according to the experiment.

• Journal of The Korean Association For Science Education
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• v.39 no.5
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• pp.655-668
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• 2019

In this study, we investigated the middle school students' processes of scientific graph construction from the perspective of the problem solving process. Ten 9th graders participated in this study. They constructed a scientific graph based on pictorial data depicting precipitation reaction. The think-aloud method was used in order to investigate their thinking processes deeply. Their activities were videotaped, and semi-structured interviews were also conducted. The analysis of the results revealed that their processes of scientific graph construction could be classified into four types according to the problem solving strategy and the level of representations utilized. Students using the structural strategy succeeded in constructing scientific graph regardless of the level of representation utilized, by analyzing the data and identifying the trend based on the propositional knowledge about the target concept of the graph. Students of random strategy-higher order representation type were able to succeed in constructing scientific graph by systematically analyzing the characteristics of the data using various representations, and considering the meaning of the graph constructed in terms of the scientific context. On the other hand, students of random strategy-lower order representation type failed to construct correct scientific graph by constructing graph in a way of simply connecting points, and checking the processes of graph construction only without considering the scientific context. On the bases of the results, effective methods for improving students' ability to construct scientific graphs are discussed.