"We Actually Saw Atoms with Our Own Eyes". Conceptions and

Research: Science and Education edited by

Chemical Education Research

Diane M. Bunce

“We Actually Saw Atoms with Our Own Eyes” Conceptions and Convictions in Using the Scanning Tunneling Microscope in Junior High School

The Catholic University of America Washington, D.C. 20064

Vickie M. Williamson Texas A & M University College Station, TX 77823

Hannah Margel, Bat-Sheva Eylon, and Zahava Scherz* The Science Teaching Department, The Weizmann Institute of Science, Rehovot, Israel; *[email protected]

The structure of matter is a fundamental concept in science instruction in secondary schools. The particulate nature of matter has been traditionally introduced in the 7th grade in an early stage of junior high school (JHS) science. In the last decade there has been considerable interest among researchers regarding students’ conceptions of the structure of matter. Numerous studies have consistently shown that many JHS as well as high school (HS) students have conceptual difficulties in understanding the ideas associated with the particle theory, despite considerable effort spent on this topic in school (1–13). Researchers have suggested several possible causes for students’ difficulties in understanding the particulate nature of matter. One main reason is the fact that, in science, materials are described in three ways: macroscopic, microscopic, and symbolic (14). Several studies have shown that many students do not understand the meaning of these three ways of representing materials, and they do not easily relate and shift from one way to the other (3, 4). Studies have also shown that students tend to combine the macroscopic continuous model with the microscopic particulate model, thereby producing hybrid models (10). Some students describe matter as a continuous substance, containing the particles of the substance (1). Kozma et al. (15) suggest that material sciences curricula should guide students to use visual and verbal representations of materials in conjunction with associated phenomena discussed in the classroom. Johnson (10) claims that some difficulties are being unnecessarily created for the students by inadequate instructional methods. Gabel (12) shows that textbooks can cause misconceptions. Other researchers have suggested that those teachers who lack a sound scientific knowledge could produce misconceptions (16, 17). The question that should be addressed in this context is whether it is possible to learn and desirable to teach the particulate nature of matter in JHS. Fensham (18) claims that because the particulate nature of matter is such a difficult subject, its instruction should be delayed to advanced high school studies. However, several educators think that JHS students can understand this topic. Piaget and Inhelder (19) suggest that the atomistic ideas begin to develop from the age of ten. Rosen and Rozin (20) demonstrate that many fiveyear-old children understand that substances may be broken up into tiny pieces, too small to be seen. Skamp (21) presents evidence that suggests that upper elementary students can be taught about the particulate nature of matter in a meaningful way. Samarapungavan (22), who investigated elementary school students’ naive understanding of the particulate nature of matter (ages 7–10), speculates that young 558

Journal of Chemical Education

•

children first develop local frameworks particular to different classes of substances, then slowly expand those frameworks to include a wide range of substances. Teaching the particulate nature of matter in JHS requires appropriate instructional methods. Indeed, several investigators believe that understanding the particulate nature of matter is a process that involves a conceptual change. Laverty and McGarvey (23) claim that the conceptual change that is required to reach the particle model is unlikely to be brought about by formal traditional teaching methods. Telling the students that matter consists of particles that are too small to be seen, does not lead to an understanding. In contrast, a constructivist approach, in which the students are encouraged to participate in debates about the meaning of alternative statements, may offer a way forward. Nussbaum (24) claims that learning the particle theory is a lengthy process of conceptual change, but it can be learned meaningfully if appropriate instructional methods are used. Margel, Eylon, and Scherz (25) report on a three-year longitudinal study investigating the changes in JHS students’ conceptions of the structure of matter in conjunction with the development of a new curriculum aimed at improving students’ conceptualization of matter. They show that students who studied the structure of matter according to a constructivistic spiral curriculum (26–28) had developed the conceptualization of the particulate nature of matter in comparison to students who studied this topic with a traditional declarative curriculum. Nowadays, a new avenue of teaching the structure of materials is possible, as a result of the development of high-resolution microscopes such as the scanning tunneling microscope (STM), which enables inspection of material at the atomic level resolution (Text Box 1). The availability of this cutting-edge research tool raises the question as to whether we can utilize it in the process of teaching the particulate nature of matter. There is a disagreement among science educators about this issue. In a few textbooks the following kind of statement can be found, “We know that atoms and molecules exist because we can see them” (30). De Vos (31) argues with this statement and explains: We can see atoms and molecules because we know they exist. Interpreting the pictures as convincing evidence for the existence of atoms and molecules requires a long and difficult learning process. The ability to see atoms is not a start but a result of this learning process. Most scientists were already convinced of the reality of atoms and molecules long before these pictures become available.

In recent years, there have been some reports about using

Vol. 81 No. 4 April 2004

•

www.JCE.DivCHED.org

Research: Science and Education

STM in science courses at the university undergraduate level (32, 33) and in some high school chemistry courses (34–37). However, to the best of our knowledge there have been no reports describing the use of STM in teaching JHS students. Goals of the Study The main objective of this exploratory study was to examine the feasibility and the potential contribution of using the STM in JHS as an instructional tool for learning about the particulate nature of matter. More specifically, we studied the following questions: 1. What are teachers’ opinions regarding the educational potential of STM as a learning tool in JHS? 2. How does STM contribute to students’ knowledge about the particulate nature of matter? 3. How does STM contribute to students’ conviction in the particulate nature of matter? 4. How do these contributions depend on students’ initial conceptions? 5. What are JHS students’ opinions regarding the STM activity?

Method Sample The sample consisted of a group of 15 JHS teachers who participated in a national course for teacher leaders and 60 8th grade students. At the time of our experiment, the students had already studied the particulate nature of matter, atoms, molecules, size and units, models, elements, compounds, mixtures, and the structure of the atom.

Procedure The STM Experience: A special activity with the STM was designed for JHS teachers and students. The activity lasted 1.5 hours and took place in a research laboratory in the Materials and Interfaces Department of the Weizmann Institute of Science, where the STM is used for research purposes. After receiving a short introduction about the STM and explanation of its functions and applications, the teachers and the students were involved in several tasks: 1. Preparing a sample of graphite and then observing the sample using the STM. 2. Analyzing a few STM pictures provided by the STM laboratory, using the computer. 3. Matching a few objects (e.g., a compact disk and a shiny metal object) to their corresponding STM pictures. 4. Discussing issues relevant to the STM activity, such as orders of magnitude and small units (angstroms and nanometers).

Teachers’ Activity: First, the teachers were asked to read an article about STM technology. Next, they went through the STM experience and filled out a questionnaire in which they had to give their opinion, as experts, about different aspects of using the STM with JHS students. After the STM experience teachers participated in a plenary discussion about the STM activity. Students’ Activity: First, the students filled out a preliminary questionnaire about their conception of the structure of matter and the extent to which they believe in the particulate nature of matter. Next, they carried out the same four www.JCE.DivCHED.org

•

Scanning Tunneling Microscope (STM) STM is a scientific research tool used by scientists, especially in studying interfaces and surface analysis of materials. The STM is a microscope with a resolution sufficient to resolve single atoms. A tip of the STM scans the surface while the electron tunneling current is measured. The current is a function of the distance between the electrode and the surface. The current increases when the tip is positioned directly above the surface of an atom. A computer interprets the collection of currents measured at the STM tip into an image. Atoms appear as bright spots in the image; the periodic array of atoms is clearly visible in the images of conducting materials such as gold, platinum, silver, nickel, copper, and graphite. A more detailed description of the STM appears in Giancarlo, L. C. et al. (29). Text Box 1. The scanning tunneling microscope (STM).

I. How did the STM activity contribute to: a. Your professional knowledge in science and technology? b. Your conception of the structure of matter? II. What are your opinions regarding the educational potential of STM as a learning tool in JHS? a. Is viewing the material through the STM important to the students’ understanding of the particulate nature of matter? b. Is the STM activity suitable for JHS students? c. May the use of the STM cause difficulties for JHS students? d. At what stage of teaching the particulate nature of matter is it worthwhile to integrate the STM activity? Text Box 2. Teachers’ feedback questionnaire about the STM activity.

tasks with the STM as was previously described. The students concluded by filling out a questionnaire.

Research Tools 1. Teachers’ feedback questionnaires given after the STM activity. 2. Teachers’ discussion (videotape). 3. Students’ questionnaires (before and after the STM activity) consisted of open questions, and Likert-type questions related to their activities. 4. Predict, Observe, and Explain (POE) questionnaires, given during the STM activity, in which the students were asked to draw an atomic image of graphite before (predict) and during the STM experiment (observe), and explain their drawings. 5. Informal discussions with several students about their answers (after the completion of all questionnaires).

Findings and Discussion

Teachers’ Opinions about the STM Activity After the STM activity, the teachers filled out a questionnaire (Text Box 2) in which they gave their opinion, as experts, about different aspects of using the STM. The re-


•


559


sults indicate that the STM activity had two main effects regarding teachers’ content knowledge and the pedagogical and didactical aspects. Content Knowledge The teachers emphasized the contribution of the STM activity to their professional knowledge in science and technology. The teachers were extremely impressed with the exposure to a cutting-edge tool in science and technology.

Pedagogical and Didactical Aspects The results of the teachers’ questionnaire indicated that 67% of the teachers pointed out that viewing the material through the STM is important for students’ learning about materials.

“The fact that we saw the atoms with our eyes was impressive.”

However, only 40% of the teachers thought that actual work with the STM is in fact suitable for JHS students.

“Now I can tell my students from firsthand experience that I saw atoms.”

“The students lack basic knowledge and therefore are not able to comprehend how the instrument works.”

“The idea of miniaturization is impressive: a relatively small instrument that does great things. I expected a huge, complicated instrument and suddenly, through this small instrument and a computer, the same computer that I have at home, it is possible to get to tremendous scientific achievements.”

About 93% of the teachers were concerned that this activity could cause conceptual difficulties for JHS students.

“This is a real connection between science and technology. This is how technology advances science.” “There is no science without technology and there is no technology without science.” “I was exposed to the cutting-edge of science and technology.”

The teachers also reported that the STM activities contributed to their understanding of the structure of matter by providing an “experimental proof ” of the existence of particles in substances. “Our confidence in the model has grown: There is proof that what we teach in class with great skepticism is true.” “We received reinforcement of what we teach—that matter is made of particles.” “I realized that the lines that symbolize chemical bonds do not appear in the microscope picture.” “Until now, I did not understand well the picture of the atoms using the STM shown in the textbook. After the visit I will be able to explain to the students what they see.”

Predict: You are going to see a picture of graphite through STM. Draw a picture of what you think it will look like. Explain your drawing. Observe: Draw a picture of what you really see. Explain: Did your first drawing match what you really saw? Explain. Text Box 3. The Predict, Observe, and Explain questionnaire.

Table 1. The Distribution of Students’ Predictions and Obser vations in the POE Questionnaire (N = 56) Type of Drawings

Prediction of Students (%)

Observation of Students (%)

Microscopic

73.2

30.3

Macroscopic

12.5

14.3

0.0

30.4

14.3

25.0

Realistic No drawings

560


•

“When a student sees and touches the entire system, he ‘believes’ much more.” “It is important to show how advanced the technology is.”

“This activity is too difficult for JHS students.”

“The pictures are not clear or illustrated enough.” “The students will not understand what they are seeing.” “The students have difficulty understanding the measurement of small units.” “You cannot always reach atomic resolution and you see continuous pictures.” “The pictures are not clear; it is difficult to decipher what is seen.”

About 87% of the teachers said that the introducing this activity should take place after completing the instruction of this topic in class. They claimed that this type of activity could not replace the meaningful constructing of the particle model. The other 13% suggested introducing the STM activity before teaching the topic to enhance motivation. In the discussion with the teachers, which took place after the activity, several questions were raised: “Did we really ‘see atoms’? Or maybe it was an image?” “What is the implication of ‘seeing’ when referring to extremely small particles?” “What model of the atom do we have in mind when we say ‘we saw atoms’?”

Summary The teachers claimed that viewing materials through the STM contributed to their own professional development. Most of them were skeptical and were concerned about the difficulties associated with an STM activity for JHS students, although many agreed that it might help the students in several aspects.

Students’ Learning from the STM Activity The Predict, Observe, and Explain (POE) questionnaire, a tool for probing students’ understanding (38), was used to probe students’ conceptions of the particulate nature of graphite (Text Box 3). Fifty-six students (out of 60) answered the POE questionnaire. The distribution of the students’ drawings in this questionnaire is shown in Table 1 and typical examples of students’ answers are given in Table 2. Students’ drawings of their predictions and observations were classified into three categories: Microscopic : Some students represented the graphite by a variety of particulate drawings: a lattice, separate particles, circles


•

www.JCE.DivCHED.org

Research: Science and Education Table 2. Typical Examples of Students’ Answers to the POE Questionnaire Student

Predict

Observe

Explain

1

We really didn’t see atoms, but we did see the location of the needle, which indicates the location of the atoms.

2

The size of atoms was different than what I expected.

3

I drew chemical bonds that do not actually exist in reality. We really saw the surface area of graphite.

4

I knew the structure of graphite, but seeing it helped me understand its structure.

5

I saw the surface area and not a specific atom.

6

I drew a model of molecules, but using the instrument I could see the lattice only.

7

I drew graphite as a circle and that is what I saw.

8

I did not know how it was going to look like.

9

I did not know how it was going to look like.

www.JCE.DivCHED.org

•


•


561

Research: Science and Education connected with lines, a layer of atoms, Bohr’s model, molecules, or a single atom (e.g., the predictions of students 1–7 in Table 2). Macroscopic : Some students represented the graphite macroscopically (e.g., the prediction of student 8 in Table 2). Note that some of these drawings could not be interpreted clearly. Realistic : Because of technical problems concerning the STM activity, the equipment did not yield atomic resolution. Therefore, the actual image that the students were able to see consisted of black and bright areas. Some students drew what they actually saw, as exemplified in the observations of students 1, 2, 3, and 9 in Table 2.

Thirty percent of the students drew bright and black areas after the STM activity. It seems that about half of the students who drew microscopic pictures before the STM activity changed their presentation to a realistic one, whereas the other half held their microscopic representation. This shift does not reflect a change in the students’ microscopic conceptions as illustrated in their “explanations” which will be discussed later. About 14% of the students drew graphite macroscopically, and 25% of the students did not draw at all. These students probably had difficulty in grasping the difference between their microscopic school model and the real image in the STM. After the STM activity, the students provided written explanations as shown in the third column in Table 2. The different types of explanations are shown in Table 3. Some of the students related in their explanations to “incorrect” predictions. For example, students who initially drew lines that represented chemical bonds explained that these lines do not actually exist in reality (see for example, explanations of students 2, 3, and 6, in Table 2). Other explanations related to the actual observation of the surface area, to the way the STM works and to the dark and bright areas observed in the experiment. Some students expressed in their explanation their surprise in relation to the actual STM image. The results in Table 3 shows that 57% of students actually explained the STM image using microscopic terms. Another aspect of students’ learning through the STM experience was probed by two open-ended questions about the STM experience that were given to the students after the STM activity (Table 4). The answers were analyzed and categorized.

Table 3. The Distribution of Students’ Explanations in the POE Questionnaire (N = 56) Type of Explanations

This Response (%)

Examples from Table 2

Explanations about “incorrect” predictions.

35

Students 2, 3, and 6

Explanations related to the image of the surface area.

10

Student 5

Explanations related to the way the STM works.

12

Student 1

Explanations expressed students’ surprise with respect to the STM image.

30

Students 8 and 9

No explanation given.

13

—

The following are some relevant quotes from students: “We saw the image of the surface.” “I saw the image of the surface of matter at the atomic level.”

Analysis of the students’ responses to the POE questionnaire as well as to the questions presented in Table 4 indicate that students actually improved their ability to explain phenomena such as STM pictures and function. The students showed an ability to reflect on and to correct wrong predictions. Students improved their scientific vocabulary and were able to correctly use the terminology they had learned through the STM experience. For example, they were careful to use the term “scanning tunneling microscope” and not to simply call it a “microscope”. They also correctly used the term “surface”, with which they got acquainted for the first time during the STM activity. Impressed by the powerful STM technology, students were able to explain its structure and the way it works: “I saw a scanning tunneling microscope, that tests the surfaces of various samples by means of a needle that passes over the material.” “We really didn’t see atoms, but we did see the location of the needle, which indicates the location of the atoms.”

Table 4. Students’ Responses about Their Learning from the STM Activity (N = 60) Question

Students’ Answers

1. If your friends asked you what you have seen at the Weizmann Institute of Science, what would you tell them?

2. Describe briefly what you learned from the visit that you did not know previously.

562


•

This Response (%)

“The STM”

85

“Materials and structure of matter”

57

“Graphite”

25

“The storing of data on a disk”

10

“We saw the actual surface of matter.”

10

“The STM and its function”

52

“Orders of magnitude”

37

“Materials and structure of matter”

27

“The structure of matter”

20

“The storing of data on a disk”

10


•

www.JCE.DivCHED.org


Table 5. Students Express Their Conviction in the Particulate Nature of Matter before the STM Learning Activity and Explain Their Choice (N = 60) Statements

Students’ Explanations

I am convinced that matter consists of small particles.

Belief in teachers and scientists.

This Response (%) 93

“This is what I was taught, and I believe my teacher.” “Scientists have proved this and I believe them.” The particulate nature of matter was taught in class. “We learned the particulate nature of matter in class.” “The experiments that we carried out in class convinced me.” The particle model explains many phenomena. “If oxygen was not made of particles, we would not be able to breath it.” “The particle model successfully explains the states of matter.” “People look at something and see only the complete product, but I believe that there are particles which make up compounds and mixtures are made of. If not, how would it be possible to have substances with similar properties?” There is no better explanation. “No one has proved otherwise.” “I see no reason not to believe it.” “The particles are the building blocks of elements—without particles, what is matter made of?”

I’m not convinced that matter consists of small particles.

Theories can change.

7

“Because many things in the past centuries, which were believed to be true, were later found not to be true.” Lack of belief in the particle model. “Until I see it, I won’t believe it.” “Not everything is made of particles, they may consist of other things.”

Students’ Conviction in the Particulate Nature of Matter Before the STM activity, students were asked about their conviction in the particulate nature of matter in two ways: a. The students were asked to choose one of two statements regarding their conviction in the fact that matter is made of small particles, and to explain their choice. The students’ explanations were classified into several categories. Table 5 summarizes the students’ choices and explanations. b. Before the activity, the students also filled out a questionnaire that compared their previous knowledge with their conviction in the particulate nature of matter (Table 6).

The results in Table 6 show that although most students knew about the particulate nature of matter, their conviction in it was lower (see the results of statements 2–4). The results for statement 2 and 4 were reversed because they were phrased “negatively”. A t test comparing students’ conception of the particulate nature of matter with their conviction yielded a significant difference both for the mean score of conviction ( p < 0.0001), and for each of the conviction statements 2–4 ( p < 0.001). After the STM activity, the students were asked to react to the following statements: “We didn’t see atoms. What we saw was not convincing” and “There is no need to actually work with STM; it is enough to see the images in the textbook”. Most of the students (75% and 73%, respectively) did not agree with these statements. www.JCE.DivCHED.org

•

Students’ convictions after the STM experience were directly examined (Table 7). The results show that 45% of the students did not change their conviction in the particulate nature of matter. Those students were initially convinced in the particulate nature of matter. Fifty-five percent of the students increased their conviction in the particulate nature of matter: 40% of the students increased moderately their conviction in the particulate nature of matter; 15% of the students showed strong change in conviction in the particulate

Table 6. Students’ Conception of and Conviction in the Particulate Nature of Matter before the Activity (N = 60) Meana,b (SD)

Statements about Conception and Conviction 1. According to recent science theory, materials consist of small particles.

3.8 (0.4)

2. Despite our studies I am not sure that materials consist of small particles.

3.5 (0.8)

3. I don’t need to see atoms in order to believe that they exist.

2.9 (0.7)

4. I’ll believe in atoms only when I see them.

3.2 (1.0)

a

On a scale of 1 (don’t agree) to 4 (absolutely agree).

b

Mean score of statements 2–4 is 3.2 (0.7).


•


563


nature of matter. A total of 100% of the students were convinced in the particulate nature of matter after the STM activity.

Contribution of the STM Activity to Knowledge and Conviction: Dependence on Students’ Initial Conceptions The previous sections showed that the STM activity contributed both to students’ knowledge and to their convictions. In this section we will further examine how this contribution depended on students’ initial conceptions. Contribution to Knowledge According to the results of the POE questionnaire (see Tables 1 and 2), one can see that the students who demonstrated a particulate conception of matter before the STM activity showed a deeper understanding of the particulate nature of matter after the STM activity than the others. Moreover, the students who demonstrated a particulate conception of matter before the STM activity were able to relate to their predicted drawings and knew how to explain their wrong predictions. They also explained how the STM functions (see the explanations of students 1–6 in Table 2). In contrast, the students who did not demonstrate a particulate conception of matter before the STM activity were not able to explain well what they had seen (see the explanations of students 8 and 9 in Table 2). Contribution to Conviction Correlation between change in conviction (Table 7) and initial conviction (statement 2 in Table 6) was calculated using a Kendall tau (τ) since both variables are ordinal. The value of τ = ᎑0.46 (Z = ᎑5.2; p < 0.0001) shows that the variable “change in conviction” is “negatively” correlated with the variable “initial conviction”, that is, the lower the initial Table 7. Changes in Students’ Conviction in the Particulate Nature of Matter (N = 60) Students Who Agreed (%)

Change in Conviction

I was convinced before that materials consist of particles, and also now I am convinced.

45

No change

I was convinced before that materials consist of particles, and now I am even more convinced.

40

I was not sure that materials consist of particles but now I am convinced.

15

Statement

Moderate

conviction, the higher the change in conviction. Students who initially were not sure about the particulate nature of matter and claimed, “Despite our studies, I am not sure that matter consists of small particles” increased their conviction and even changed their mind as a result of the STM activity.

Students’ Opinions Regarding the STM Activity The students were asked to refer to a statement about the STM activity (Table 8) before and after the activity. The results in Table 8 show that the students who had participated in the study had high expectations regarding the activity. Most students presumed that “viewing atoms” with the STM would contribute to their understanding and would demonstrate the existence of the particulate nature of matter. After the activity took place, most of the students still had positive views regarding the STM activity. Only few students mentioned in their explanation that the activity was difficult for them. The results in Table 8 show that most of the students claimed that the STM experience indeed contributed to their understanding of the particulate nature of matter. Yet the post-activity number was less than the pre-activity number. The difference is statistically significant ( p < 0.001). A detailed analysis shows that students who initially had low expectations regarding the contribution of the STM activity to the understanding of the particulate nature of matter did not change their opinion after the STM activity. On the other hand, those who had high expectations regarding the STM activity changed their opinion to a more realistic view. To examine the affective aspects of the STM activity, the students were asked to indicate what was their strongest impression from the STM experience. The students’ responses were categorized as shown in Table 9. It seems that the techTable 8. Students’ Responses about the Educational Potential of STM as a Learning Tool (N = 60) Statement

Students’ Answers Meana (SD)

Pre

2.8 (0.5)

Post

2.5 (0.4)

“Viewing atoms” using the STM is important for students to understand the particulate nature of matter. Explain. a

On a scale of 1 (don’t agree) to 3 (agree).

Strong Table 9. Students’ Responses toward the STM Activity This Responsea (%)

Statement

I was not sure that materials consist of particles, but now I am a little bit more convinced.

0

I was not sure that materials consist of particles and even now I am also not sure about it.

0

_ I was particularly impressed by:

_

a

564

STM Activity


•

“The structure of matter as seen in the computer image.”

46

“The small size of the microscope.”

32

“The instrumentation.”

29

“Everything.”

43

Affective aspects; N = 60.


•

www.JCE.DivCHED.org


nological state-of-the-art aspects of the STM impressed all students:

ficulties in up scaling such an activity to a larger population in JHS:

“I was particularly impressed by technologies of such small dimensions.”

• Students’ visits in research institutions disrupt the scientists’ work.

“I was mostly impressed with the capability of such a small instrument. I expected it to be large and impressive, but to my surprise it was very small.”

• The use of the laboratory equipment needed for an STM experiment is relatively expensive.

In informal discussions students commented that the STM activity contributed to their knowledge about the relationship between science and technology. They regarded the STM activity as an interesting and exciting experience of observing instruments and scientists in action. Conclusions and Implications for the Future The results of this study suggest that the activity with the STM was appropriate for our JHS students, despite the teachers’ concerns about the conceptual difficulties that such an activity might create. Students felt that the STM activity contributed to their learning and understanding of the particulate nature of matter. The main contribution of observing the particulate structure of matter by means of the STM was students’ gain in confidence and conviction in the particulate nature of matter. It is generally accepted that active visualization-based learning can improve understanding and retention (39), but at the same time interpretation of visual experience highly depends on existing knowledge. This is evident also in the present study. One must realize that interpreting the pictures of the STM, as convincing evidence for the existence of atoms, requires a solid understanding of the particulate model. The students who demonstrated a particulate conception succeeded in “seeing” atoms (although what they actually saw in the experiment were bright and dark areas). The students who did not demonstrate a particulate conception before the STM activity gained confidence in the existence of atoms, although they did not manage to explain well what they saw. Although the STM activity contributed significantly to students’ learning, it cannot replace an intensive learning process that constructs a thorough understanding of the particulate nature of matter. A constructivist approach, in which the students are encouraged to argue among themselves about the meaning of various statements, may offer a way forward (24). Hence appropriate instruction is essential, yet the STM activity can markedly enhance and contribute to students’ understanding and conviction of the particulate nature of matter. Another contribution of the STM is the possibility of demonstrating the use and the power of new technologies. “Nanoparticles” and miniaturization technology are at the forefront of science, and therefore it is important that students understand the particulate structure of matter and the implications of such small orders of magnitude. In addition, measurements are central to science and it is impossible to teach science without the concept of measurement. Therefore, it is important that students experience the use of the stateof-the-art instruments, used in modern scientific research. Our experience shows that it is advisable to combine special activities such as this with science and technology instruction in junior high schools. However, there are some difwww.JCE.DivCHED.org

•

• It is difficult to bring large groups of students into small research laboratories.

One way to overcome these difficulties would be to purchase the STM instrument for central JHS laboratories. The STM itself becomes less expensive with the development of new technologies. An STM for instructional purposes is now available for about $5000. However, it would be necessary to instruct school lab technicians and teachers how to maintain the instrument. Another more practical possibility is to videotape the experiments done with the STM and to show them to the students together with appropriate explanations and activities. An additional way is an interactive instruction through the Internet, such as the one reported by Ong for the upper classes in high school (36). These activities were designed to carry out experiments that use the instrument by “remote control”. This arrangement leads to the possibility of discussing an experiment performed by a student in a research laboratory, and creating a store of STM pictures of materials for learning and discussion in the classroom. To conclude, this exploratory study shows that STM can be used in JHS as an additional educational tool for learning about the particulate nature of matter. The STM has the potential to improve JHS students’ understanding and conviction in the existence of atoms. The STM activity also demonstrates the use and the power of state-of-the-art technologies. Acknowledgments The authors would like to thank Reshef Tenne, head of the Materials and Interfaces Department at the Weizmann Institute of Science, for his suggestion to use the STM as a learning tool, and Sydney Cohen for conducting the STM activity in his laboratory in the Chemical Services Department at the Weizmann Institute of Science. Literature Cited 1. Novick, S.; Nussbaum, J. J. Sci. Educ. 1978, 62, 273–281. 2. Brook, A.; Briggs, H.; Driver, R. Aspects of Secondary Students’ Understanding of the Particulate Nature of Matter; Children’s Learning in Science Project; Center for Studies in Science and Mathematics Education: University of Leeds, 1984. 3. Ben-Zvi, R.; Eylon, B.; Silberstein, J. J. Chem. Educ. 1986, 63, 64–66. 4. Ben-Zvi, R.; Eylon, B.; Silberstein, J. Educ. in Chem. 1988, 25, 89–92. 5. Andersson, B. Studies in Sci. Educ. 1990, 18, 53–85. 6. Millar, R. In Relating Macroscopic Phenomena to Microscopic Particles; Lijnse, P. L., Licht, W., De Voss, W., Waarlo, A. I., Eds.; University of Utrecht; Utrecht, The Netherlands, 1990. 7. Renstrom, L.; Andersson, B.; Marton, F. J. Educ. Psych. 1990, 82, 555–569.


•


565

Research: Science and Education 8. Gabel, D. L. J. Chem. Educ. 1993, 70, 193–194. 9. Driver, R.; Squires, A.; Rushworth, P.; Wood Robinson, V. Making Sense of Secondary Science—Research into Children’s Ideas; Routledge: London, 1994. 10. Johnson, P. Inter. J. Sci. Educ. 1998, 20, 393–412. 11. Krnel, D.; Watson, R.; Glazar, S. A. Int. J. Sci. Educ. 1998, 20, 257–289. 12. Gabel, D. L. J. Chem. Educ. 1999, 76, 548–553. 13. Sanger, M. J. J. Chem. Educ. 2000, 77, 762–766. 14. Johnstone, A. H. J. Comp. Assist. Learn. 1991, 7, 75–83. 15. Kozma, R. B.; Chin, E.; Russell, J.; Marx, N. J. Learn. Sci. 2000, 9, 105–143. 16. Kokkotas, P.; Vlachos, I.; Koulaidis, V. Int. J. Sci. Educ. 1998, 20, 291–303. 17. Del Pozo, R. M. J. Sci. Educ. 2001, 23, 353–371. 18. Fensham, P. In The Content of Science: A Constructivist Approach to its Teaching and Learning; Fensham, P., Gunstone, R., White, R., Eds.; Falmer: London, 1994; pp 14–28. 19. Piaget, J.; Inhelder, B. The Child’s Construction of Quantities: Conservation and Atomism; Routledge and Kegan Paul: London, 1974. 20. Rosen, A. B.; Rozin, P. Develop. Psych. 1993, 29, 300–311. 21. Skamp, K. School Sci. Rev. 1999, 81, 87–96. 22. Samarapungavan, A.; Nakhleh, M. B. J. Res. Sci. Teach. 1999, 36, 777–805. 23. Laverty, D. T.; McGarvey, J. E. B. Educ. in Chem. 1991, 28, 99–102. 24. Nussbaum, J. Teaching Science for Understanding: A Human Constructivitist View; Academic Press: New York, 1998; Chapter 6. 25. Margel, H.; Eylon, B.; Scherz, Z. Junior High School Students’ Conceptions of the Structure of Matter: a Longitudinal Study

566


•

26.

27.

28. 29. 30. 31.

32. 33. 34. 35. 36.

37. 38. 39.

Paper Presented at the annual meeting of National Association of Research in Science Teaching (NARST), St. Louis, MO, 2001. Nussbaum, J. The Structure of Matter: Vacuum and Particles; Weizmann Institute of Science: Rehovot, Israel, 2000 (In Hebrew). Yayon, M.; Margel, H.; Scherz, Z. From Elementry to Complex Structure; The Weizmann Institute of Science: Rehovot, Israel, 2000 (In Hebrew). Margel, H. About Fibers; The Weizmann Institute of Science: Rehovot, Israel, 1999 (In Hebrew). Giancarlo, L. C.; Fang, H.; Avila, L.; Fine, L. W.; Flynn, G. W. J. Chem. Educ. 2000, 77, 66–71. Atkins, P. W. Physical Chemisrty, 3rd ed.; Oxford University Press: Oxford, United Kingdom, 1986. De Vos, W. In Relating Macroscopic Phenomena to Microscopic Particles; Lijnse, P. L., Licht, P., De Vos, W., Waarlo, A. I., Eds.; University of Utrecht; Utrecht, The Netherlands, 1990. Coury, L A., Jr.; Johnson, M.; Murphy, T. J. J. Chem. Educ. 1995, 72, 1088. Wagner, K. Sci. Teach. 1994, 61, 24–27. Rapp, S. C. J. Chem. Educ. 1997, 74, 1087–1089. Markham, J. R. J. Chem. Educ. 1998, 75, 247–248. Ong, E. W.; Razdon, A.; Gracia, A. A.; Pizziconi, V. B.; Ramakrishna, B. L.; Glaunsinger, W. S. J. Chem. Educ. 2000, 77, 1114–1115. Maye, M. M.; Luo, J.; Han, L.; Zhong, C. J. J.Chem. Educ. 2002, 79, 207–210. White, R.; Gunstone, R. Probing Understanding; The Falmer Press: London, 1992. Greenberg, R.; Kolvoord, R. A.; Magisos, M.; Strom, R. G.; Croft, S. J. Sci. Educ. Tecnol. 1993, 2, 469–480.


•

www.JCE.DivCHED.org

"We Actually Saw Atoms with Our Own Eyes". Conceptions and

Recommend Documents