APPLICATION TO CLASSROOM

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Fig. 4-6. Alkali contents in vegetable and fruit versus the conductivities

Based on the correlations shown in Fig. 4-6, it can be assumed that the total contents in the sport drink like Pocari Sweat is about less than 1.0x10^5 mol/g. This is even below Cabbage juice, Radish juice and Carrot juice, due to its conductivity is only 0.0020 S.cm^1.

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following three periods the students examined the conductivity of electrolyte solutions, the conductivity of vegetable and fruit juice solutions, and acid-base titration for vegetable and fruit ashes. All the sample solutions and materials were readily prepared for students before the lessons. Finally, the students were able to obtain the same results as shown in Table 4-6 and Table 4-7. Though, the results from the portable conductivity meter (Shimadzu portable Kohlrausch Bridge BF-62A) were measured by the instructor.

Before the experiment, students were asked to predict and explain what would happen to the conductivity when the concentration of electrolyte in solution decreased or increased, based on their background knowledge on how electricity passed through a material. Since Pocari Sweat sports drink is a common drink in Japan that people often use to supplement ions in their body after exercising, the lesson presenter asked students whether people could use vegetable or fruit juices instead of Pocari Sweat sports drink after they did exercise. Such introductory questions were of key importance in the lesson because they effectively motivated students towards scientific investigation. The most impressive activity for students was the conductivity determination of vegetables and fruits. The students could hardly wait to conduct their experiment to find out whether their predictions about whether Pocari Sweat sports drink was better than the vegetable and fruit juices, were correct or not.

As shown in Fig. 4-5, the students understood that electrical conductivities for a certain electrolyte solution differed at different concentrations. In particular, they observed that conductivity increased with increasing concentration. They also could reveal clearly that a higher charge of cation showed a higher conductivity at similar concentrations, and that the electrical conductivity of different electrolyte solutions increased with respect to the number of ions dissociated from the species. In Table 4-5 and Table 4-6, the students surprisingly realized that some vegetable and fruit juices such as cabbage, radish and carrot could provide more electrolytes (ions) than Pocari Sweat sports drink. This result surprised the students so

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much that they said they would drink juice instead of Pocari Sweat sports drink to supplement ions to their body when they sweat.

The total content of the electrolyte was also revealed to the students through acid-base titration experiments. The students could understand the clear relationship between the total content of the electrolyte, and alkali in the corresponding ash derived solutions (Fig. 4-6). In addition, the students learned that although vegetables and fruits contained organic and inorganic substances, they mostly contained inorganic substances when they were burned to ash. They observed the ash solution turned pink when a few drops of phenolphthalein were added, which clearly proved its alkalinity.

2. Evaluation of the developed teaching and learning materials

<Knowledge Improvement>

After the lessons, most of the students could understand the lesson concepts have been taught. Responding to the questionnaires, no one responded “did not understand at all”, but most of them chose “clear understood” and “understood” (Fig. 4-7). They improved their knowledge related to the teaching contents significantly while comparing before and after the lesson. As shown in the pre/post test results, most of the students could achieve high scores to each of the questions (Fig. 4-8).

Fig. 4-7. Students evaluated their understanding of the lessons

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Clear understood

Understood Somehow understood

Did not understand

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Number of responses

Japanese students Cambodian students

102

Fig.4-8. Students’ performance on pre/post tests: (a) Japanese students, (b) Cambodian students

Q1: Definition of conductivity.

Q2: Conductivity and concentration of solutes relationship Q3: Conductivity and concentration of solutes relationship Q4: Conductivity and total contents in environmental water Q5: Conductivity and daily drinks

(The detail questions in Pre/Post Tests are attached in the APPENDIX)

Moreover, the students recognized that they could obtain several skills from the lessons they learned. As shown in Fig. 4-9, most of the students learned that carrot and radish contain more ionic contents compared to other fruit and vegetable, and many of them valued the meaning of conductivity and its measurement method as well as the relationship between the conductivity and the dissolved content concentration in the solutions. This is clearly indicated that the students could acquire the concept of conductivity of solution very well by using the developed teaching and learning apparatus and the designed activities.

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Q1 Q2 Q3 Q4 Q5

Number of correct responses

Number of Questions

Pre-Test Post-Test

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Q1 Q2 Q3 Q4 Q5

Number of correct responses

Number of questions

Pre-Test Post-Test

(a) (b)

103

Fig. 4-9. Students claimed their knowledge and skills acquired from the lessons

<Applicability>

Fig. 4-10. Feasibility of using the hand-made apparatus by the students

In general, the apparatus and activities could be appropriately applied to the students at secondary level in both Japanese and Cambodian classrooms. In the questionnaires, the students responded that they could use the hand-made apparatus without difficulty. Even

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Conductivity & Concentration relationship

Conductivity can be calculated from Resistor

Kohlrausch bridge Fruit juices like carrot and radish

has high conductivity how to determine conductivity

Resistor can be hand-made Definition of conductivity

Number of responses

Cambodian students Japanese students

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Very Easy Easy Not too easy, but

feasible

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Japanese students Cambodian students

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though some of them thought that it was not too easy, but feasible, many of them showed it is easy or very easy (Fig. 4-10). It could be noticed that, although the procedures of using the handmade apparatus are easy, it constructed based on Kohlrausch bridge which needs physic principle to interpret data. This might cause some difficulty for some students to follow.

However, the students still could use the developed apparatus and conduct the activities designed in the lessons to solve the given problem and reach to the lesson objectives.

Therefore, it was concluded that the apparatus was feasible to introduce to students in the classroom at this level.

<Students’ Satisfaction>

As shown in Fig. 4.11, for the students showed that they satisfied the lesson activities as well as the introduced learning apparatus. This means that the use of the developed hand-made apparatus could surely encourage students learned more actively and effectively in the classroom.

Fig.4-11. Students’ satisfaction of the introduced activities and the handmade apparatus.

The followings are common comments given by the students after the lessons:

- I‟ll use orange juice or vegetable juice instead of POCARI SWEAT - I am surprised that carrot is better than sport drink.

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Much satisfied

satisfied Little satisfied

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Number of responses

Japanese students Cambodian students

105

- I'll suggest my teammates to drink fruit juice instead of POCARI - I want to examine other material like coke, coffee, tea…

- At first there were many words difficult for me. But today‟s lesson give me many knowledge.

- Today‟s lesson is very interesting.

- I am surprised carrot and radish juice has a lot of fun.

- Today‟s lesson has many things.

- I have never learned this lesson. It is interesting.

- I want to come here again next week.

- I enjoyed and understand today‟s class.

- Today‟s experiment was interesting since I am interested in electricity.