A Study of Conceptual Formation and Development for Solubility in Elementary and Secondary School
Liang-Rong HsuCheng-Hua Liu
Deparetment of Natural Science Education, NationalTaichungTeachers College
Abstract
The purpose of this research was to explore students’ conceptual formation and development for solubility. The subjects include 6th, 8thand 11th grader students. The adapted methods includes POE(Predict-Observe-Explain) and interview about instance, as well as cross examinations with previous studies (Hsu and Pon, 2002). During the formation of misconception, students tend to over-generalize the relationship of “oil, density, and solubility” that formed the misconceptionof “all of oilwould soluble with water” and “density affective solubility”. This study was based on Piaget & Garcia(1989)’s model of the development of mechanism in history of science, and concluded the features of students’ conceptual development for solubility being: Students of lower grade tend to judge the solvency of a substance based on its apparent properties. When school experience increases, students have a higher tendency of reasoning the solvency based on density. Even after students acquired the concepts of acids and chemical formulas in high school, it appeared that those concepts still coexist in a student’s cognitive structure.
Keywords: Conceptual Development, Conceptual Formation, Solubility
Introduction
This study was a part of the project that was designed to explore students’ alternative conceptions ofchemistry at elementary and secondary schools in Taiwan. The present studyintends, specifically, to investigate students’misconceptions ofsolubility.
The science education literature of the past two decades includes numerous studies of young students’alternative conceptions or misconceptions aboutsolution ().The classic work of Piaget & Inhelder (1974) showed the children’s reasoning is governed by perceptual experience when they were asked to predict what would happen in term of changes inweight and volume when some sugar was dissolved in water.In the study of Driver & Russell (1982),the results show about two-third students (9 to 14-years-old English children) predicted the mass of the solution would be less than the sum of the initial masses of the sugar and water. In an interview study, Ebenezer & Erickson (1996) identified 11th grade students’ conceptions of solubility. They grouped student’s conceptions into six categories: physicaltransformation from solid to liquid, chemical transformation of solute, density of solute…, etc. In previous study Hsu & Pon (2002) found students posses notice misconception of solubility in Taiwan of grades 4, 6, 8 and 11. However, students have misconception or alternative concepts about solubility that had revealed in literature.But has no researches focus on students’conceptual formation and developmentabout solubility. The purpose of this study was to explore cross-age students’ misconceptions ofsolubility through their interaction with events in a real situation (predict-observe-explain; POE and interview about instance; IAI).
The reference model of conceptual development in this study was cited from Piaget & Garcia (1989). They had propose a model for explain the conceptual development of mechanism in history of science. We use the model to conduct the students’ conceptual development of solubility.
Method and Procedures
1.POE
The subjects included 98 6th graders, 105 8th graders and 115 11th graders (three classes for each grade, total N=318). At the onset, the researcher told the students that the task was not an examination but part of a study with the purpose to know their thoughts about solubility. Glycerin was used to be the sample for prediction matter. Before having the students predict whether it was soluble with water or not, the researcher introduced its properties, including name, boiling point, specific weight, and other important properties. Subsequently, the students were independently asked to write down their predictions with reason. At the next stage of the task, the researcher poured the sample (about 10 cc) into a beaker and stirring it about one minute. The students were asked to independently write down their observations without any discussion. Finally, the students were asked to compare their observations with their previous predictions and explain any difference that might arise.
2. Interview about instance (IAI)
The subjects included ten students of 6th, 8th and 11th graders (N=30). Those subjects has not participate the POE. There are three cards (table 1) to be as instance in the interview. Each card has a label show matter’s name, density, formula, boiling point and acidity. The mainly question in interview were which matter in three cards will soluble with water and why (the reason)?
Table 1. The instance for IAI
Label / Card 1 / Card 2 / Card 3Formula / ××OOH / ××S04 / ××（H2O）2
Name / ××油(oil) / ××酸(acid) / ××汁(juice)
State of matter / liquid / liquid / liquid
Acidity / neutral、PH=7 / base、PH=8 / acid、PH=4
Density / 0.82g/㎝3 / 0.53 g/㎝3 / 0.72g/㎝3
Boiling point / 250℃ / 180℃ / 80℃
Color / red / yellow / brown
Results and Discussion
According the results of POE, IAI and previous study (Hsu & Pon, 2002), we conduct the students’ conceptual formation and development of solubility.
- The formation of misconception about oils’ solubility--oil, density and solubility
In POE, over one-third students in each grade predicted the glycerininsoluble in water (65.5%, 75.51% and 78.9% for Grades 6, 8 and 11, respectively). After the observation, over twenty percent of the students in each grade still thought glycerininsoluble with water(15.6%, 25.7% and 34.8% for Grades 6, 8 and 11, respectively).The reason offered by each grade that has the most percentage for predictionis“everyday life”and“school experience”(27.8%, 41.9% and 60.2%for Grades 6, 8 and 11, respectively).
In IAI, the Card 1 “xx油(xx-oil)” similar with Chinese name of glycerin (甘油, sweet-oil). Most students use density to explain Card 1 would insoluble in water.
0601: ……according the word “oil”.
Researcher: why?
0601: because oil light than water, I had learned that.
Researcher: all of oil insoluble in water?
1109: yup!
Researcher: why?
1109: ……because the density of oil was small than water…then…; I don’t know, anyway, any oil can’t soluble with water.
The possible processes of the formation of misconception about oils’ solubility show as figure 1. Students aware the phenomena of oil float on water in everyday life and school experience, such as gasoline (汽油: gas-oil), varnish (油漆: oil-paint). This experience conduct students make over-generalization and formedthe misconception of “all of oil insoluble with water” and “density affect solubility”.
↙ ↘ ↗
oil float on water →oil insoluble with water →(because) the density of oil smaller than water
↘
Figure1. The formation of the misconception about oils’solubility
2. The conceptual development of solubility
According the Summarize the data of POE, IAI and previous study, we propose students’ conceptual development of solubility (Figure 2) that reference from Piaget & Garcia (1989). The figure 2 show the feature of students’ conceptual development as follow: (1) the experience of everyday life and school learning were significant source for students’ conceptual formation. But the school experience had more obvious affect of higher grades students’conceptual formation. (2) The apparent properties of matter (e.g. state, smell or color) had attractive to lower graders students when they judge of the matter’s solubility. (3) When school experience increase with grade, density become dominant role in students’ mind. (4) When students acquired the concept of acid and formula in school, it would one of criteria for judge of matter’s solubility and the concept of density that still coexist in students’ cognitive structure.
The evidence of conduct the feature in figure 2 that such as: (in brief)
(1). The subjects of lower grader students tend to focus on “apparent properties”: The results of POE indicate the percentage of the students who possess the conception “apparent properties (e.g. color, smell, liquid) affect solubility”is 24.4%, 7.1% and 0.9%for Grades 6, 8 and 11 respectively.In previous study (Hsu & Pon, 2002), the percentage of the students who thought “gasoline soluble with water because they are liquid both”is 26.2%, 15.5%, 2.8% and 2.0%for Grades 4, 6, 8 and 11 respectively. The example of such as (IAI):
Researcher: Why did you thought it (glycerin) soluble with water?
603: because it’s liquid…… and it has high density.
Researcher: What’s the mean of “state of matter”? (for soluble with water)
604: it has to be a liquid.
Researcher: What’s the mean of “state of matter”? (for soluble with water)
807: is the same.
Researcher: What’s the same ?
807: liquid……because liquid soluble with liquid.
(2). The results of POE and IAI showed the students in each grade students, obvious use density as the criteriafor solubility. Such as, in IAI has 10, 10 and 9, and in POE has 61.1%, 59.2% and 54.1% for Grades 6, 8 and 11 respectively.Additionally, Hsu & Pon (2002) found in each grader had nearly half students thought “all of oil insoluble in water because they are light than water”.
(3).Higher grade students incline to use acidity or formula as criteria for solubility. In IAI, judge by acidity (formula) has 1(0), 3(1) and 7(9) for Grade 6, 8 and 11 respectively. Hsu & Pon (2002) had found the students who thought “acetic acid solublein water because all of acid soluble with water”have 61.0%, 62.9%, 80.4% and 82.2% (4, 6, 8 and 11 Graderespectively). The example of IAI such as:
Researcher: What’s your reason?
1103: Teacher taught about sulfuric acid in chemical lesson, so, I think all of cid soluble with water.
Researcher: Why?
1103: I had diluted the sulfuric acid.
1106: The formula of this card is -OOH, it should soluble with water.
Researcher: How did you get it?
1106: Textbook and examination in school.
This study has shown that students tend to use their intuitive ideas based on individual reasons and experiences. However, it seems likely that if teachers and curriculum designers are aware of the commonly held misconceptions and factors that may contribute to their formation the situation may be quickly and greatly improved. The teaching should give students the opportunity to test and change their misunderstanding and formulate more scientific ones.
Reference (brief)
Ebenezer, J. V., & Erikson, G. L. (1996). Chemistry students’ concepts of solubility: A phenomenography. Science Education, 80(2), 181-201.
Hsu, R. Z., & Pon, U. E. (2002). A study of primary and secondary students’ misconception of the classification of matter: An example of solubility. Paper presented at third annual meeting of the Chemical Education of Republic of China. Changhua: National Changhua university.
Piaget, J., & Garcia, R. (1989). Psychogenesis and the history of science.New York: ColumbiaUniversity Press.
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