Changes in a Preservice Elementary Teachers Physics Course

Michael T. Svec Rockhurst College

William J. Boone Catherine Olmer Indiana University

Preservice elementary teachers at Indiana University are required to complete four 3-credit hour science courses (Introduction to Scientific Inquiry, Biology forElementary Teachers, Physical Science for Elementary Teachers, and a lab-based Earth Science class), as well as a 3-hour science methods course. The physical science course is offered through the Physics Department and is taken by over 95% ofpreservice elementary teachers. A member of the Physics Department teaches the course. Since the course is targeted at preservice teachers, specific course goals have been developed. The goals are to:

1. Present the ideas, methods, and excitement of physics, as well as the relevance of physics to everyday life.

2. Spark the interest of the students so they come to believe physics is enjoyable and not intimidating. Students must enjoy physics if they are to look forward to teaching physics to children.

3. Demonstrate how physics concepts can be effectively and enjoyably conveyed to children. This includes demonstrating the use of various instructional approaches and technologies to teach physics successfully.

4. Improve the students' conceptual understanding of various physics topics.

Many students enter the class apprehensive about physics. The first three goals address the students' anxiety~ reducing it so that the students will be capable of and interested in learning the physics content.

During the spring semester of 1991, microcomputer- based laboratories (MBLs) were added to the physical science course in an attempt to improve the instructors' abilities to meet course objectives. The MBLs used a sonic ranger to measure the distance, velocity, and acceleration of objects in motion. Data from the sonic ranger was then displayed as a graph on the computer

screen. Macintosh computers were used along with a software package by Vernier Software.

The New Curriculum

Why MBLs?

Why specifically incorporate microcomputer-based laboratories into a preservice elementary teacher course? MBLs provide students with critical observations which lead to true conceptual change, and they model an appropriate use of technology. MBLs' advantage over traditional labs can be found in theircapacity to graphically display data and to quickly and frequently gather data allowing students to conduct multiple experiments in the same time as a single traditional experiment. The graphs provide a richer source of information for qualitative interpretation of motion. With MBL activities, there are more opportunities for the students to explore, interpret, discuss, and experiment. The simp!e measurement procedures and the visual, ready-to-interpret graphic display allow all Students the ability to experiment. As Saunders (1992) noted, "The leamer is much more likely to be immersed in an environment rich with opportunities that evoke disequilibrium and hence give rise to the potential for cognitive restructuring" (p. 139). MBLs make such an environment possible, more so than traditional labs which might involve cumbersome and complicated data collection with air tracks and spark tapes.

MBL activities lead to significant improvements in students' abilities to learn basic science content and improve students' attitudes toward science. Thornton and Sokoloff (1990) studied the Tools for Scientific Thinking motion curriculum (Sokoloff &Thomton, 1990) which was

This material is based upon work supported in part by a grant from the National Science Foundation (Grant No. TPE-9050039). Any opinions, findings, conclusions, and/or recommendations expressed in this article are those of the authors and do not necessarily reflect those of the National Science Foundation.

Joumal of Science Teacher Education • Spring 1995 Volume 6, Number 2, Pages 79-88 Copyright ©The Association for the Education of Teachers in Science

Correspondence regarding this article should be sent to: Dr. Michael T. Svee, Rockhurst College, 1100 Rockhurst Road, Kansas City, Missouri 64110-2561

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incorporated into a traditional undergraduate physics course. Pretest results showed the students knew far less than their professors predicted. The data indicated that students frequently used a distance analogy to answer vdocity-time graph questions and had higher error rates for acceleration questions. Using MBLs, science students demonstrated lower error rates after instruction.

Barrow (1990) studied middle school preservice physical science teachers and found MBLs had a statistically significant positive influence upon students' attitudes toward the use of computers for teaching. He found that MBLs allowed students to refine their explanations and interpretations of concepts and thus helped to build student confidence. The preservice teachers saw MBLs as problem-solving tools, considering them the final authority in resolving confl ict ing opinions. Furthermore, the students considered the MB Ls a desirable altemative to traditional labs.

Researchliterature supports the use of MBLs to improve student attitudes, model appropriate use of technology, and improve content knowledge. While implementing MBLs, it was necessary to develop new laboratory exercises and revise the existing curriculum, including lectures and homework, to take advantage of the new equipment. The new curriculum impacted the class in numerous ways, and this article focuses on just the students' content knowledge. This study helped assess the impact of the new curriculum and helped determined if the labs and lectures elicited conceptual change. The results helped to determine the future role of MBLs in the course.

Why Motion?

Motion was selected as the topic for the new MBL curriculum because motion labs seemed to utilize the best features of this technology. MBLs show the computer as a device which assists in carrying out experiments and analyzing the results. It is an enabling tool students can use to explore topics in more depth. By comparison, an MBL lab focusing on temperature would replace thermometers with temperature probes. Temperature labs did not open as many new opportunities to use MBLs as motion did. The same data can be gathered in the same amount of time with a thermometer as with a temperature probe. In motion, without a sonic ranger, it is difficult and cumbersome to gather data on velocity and acceleration.

In the case of motion, many students have conceptual difficulties. For instance, students frequently do not differentiate between time intervals and an instant of time,

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average velocity and instantaneous velocity, the concepts of distance and velocity, and velocity and acceleration. In addition, students often do not see acceleration or velocity as ratios and fail to see the relationship between force and acceleration. An example of student difficulty with differentiating between concepts of velocity and distance is the belief that when two moving cars am next to each other, they have the same speed, even if one car is passing the other. These conceptual difficulties have resulted from the student's hazy conceptual framework which was created before a formal study of physics (Halloun & Hestenes, 1985; Peters, 1982; Rosenquist & McDermott, 1987; Trowbridge & McDermott, 1980, 1981).

Developing Motion Labs

Implementation of the new curriculum started with the development of new lab activities. Laboratory exercises based on Sokoloff and Thomton's (1990) Tools for Scientific Thinking were prepared. The motion labs employed a learning cycle approach. Students were first asked to predict how the graph would look for a type of motion such as walking toward the sonic ranger at a constant speed. Students then carded out the motion and compared their predictions with the resulting graph. They applied this sequence of predictions to more complicated mot ion involving stops, changes in direction, and changing velocities. Goals of the motion lab activities were to improve students' qualitative understanding of motion, focusing on creating and qualitatively interpreting distance-time, velocity-time, and acceleration-time graphs of the student's own movement, the motion of toy cars on a ramp, and the motion of a bouncing ball.

Each week, students attended two 50-minute lectures and a 3-hour laboratory. There was a homework assignment each week. A total of 10 lab sections met each week, each with a maximum of 15 students. Students were encouraged to work in cooperative groups of three.

The concepts to be covered were organized in the following fashion. The lab activities covered during the first week of the motion unit were distance-time and velocity-time graphs. The first activity engaged students in creating distance-time graphs of their own motion. Students recorded bow the graph varied depending on the direction and speed of the motion. This activity concluded with students recreating a graph given by the computer. Students translated the features of the given graph into

Journal of Science Teacher Education • Spring 1995

their own motion and tried to duplicate as best they could the given graph.

The second motion topic involved the creation of velocity-time graphs. The students experimented by walking at different speeds and directions, recording the graph produced by their motions. Students also created several distance-time graphs simultaneously with the velocity graphs to explore the relationship between graphs. The first lab activity for velocity-time required students to work with both distance and velocity graphs simultaneously. In the lab handout, the students were asked to predict the velocity graph given a distance graph. Following this prediction, students used the sonic ranger to carry out the predicted motion to verify if they were correct. Both the distance and the velocity graphs were displayed on the screen. The students then had to explain any discrepancies.

The final lab of the motion unit was devoted to the topic of acceleration graphs. Acceleration was a topic that caused the students much anxiety. The labs focused on acceleration graphs of preservice teachers' motion and how acceleration graphs related to distance-time and velocity-time graphs. Toy cars on horizontal and inclined ramps were employed for the final activities.

Lectures, homework, and tests were also adapted to match the new laboratory activities. The students had experienced graphing and interpreting graphs in an earlier required science course. Lectures preceded the labs because the students needed some experience with which to anchor their lab activities and to make the connection between what they leamed in the previous science course and interpreting graphs in the context of motion. The students were exposed to how to interpret direction, magnitude, and changes in magnitude for each of the motion graphs. The connections between known skills, such as calculating the slope, and their application in motion were demonstrated. Homework assignments and test questions included graphs of motion and required interpretation and creation of graphs.

Analysis of Results

In the fall semester of 1991, over 1130 education majors (predominantly of junior class standing) were tested on their knowledge of kinematics and graph-reading ability before and after the 3-week motion unit. These undergraduates were given a pretest which included a mixture of distance-time, velocity-time, and acceleration- time graphs. Pretests were administered during the first

Journal of Science Teacher Education • Spring 1995

week of the semester. Prior to the pretest, no lecture orlab material involving motion was presented. Following the pretest, six lectures were delivered to students for three weeks. The motion lab activities took place during three full lab sessions and a part of a fourth.

Following the presentation of lecture material, completion of labs, and an examination, a posttest constructed with graphical test items was completed by the students. The posttest was administered eight weeks after completion of the motion unit.

The pretest was a 54-item test designed by Thornton and Sokoloff (1990). The posttest had 50 items. The topics, questions, and response choices corresponding to graphic answers were in different order on the pre- and posttest. This study focused on 12 questions common to both tests plus four additional questions appearing only on the pretest. These questions were selected because specific wrong answers would indicate previously identified alternative conceptions.

The students' responses were entered into a data file and verified. The Statistical Analysis System was used to construct matrices which displayed the answers selected by students on both the pre- and posttest. For the purposes of evaluating the effect of the new curriculum material, this method of data presentation is superior to simple presentation of students' percentages selecting a specific multiple choice answer on the pre- and posttest. The matrix method allows differences in students' responses to be more easily evaluated since both pre- and posttest answers are reported. Most of the data, with the exception of the distance-time graphs, were studied using the matrix. The distance-time graph data were not studied using a matrix because these items were presented on only the pretest.

Distance-Time Graphs

Preservice elementary teachers demonstrated the ability to read and interpret distance-time graphs prior to instruction. Student knowledge was tested on four distance-time graphs (see Figure 1 for student responses on two representative questions). In general, most students correctly answered all the distance-time items on the pretest. This may be because the graph of distance- time makes common sense to the students. Students can easily see how distance is changing over a period of time; the graph looks like a time-lapsed photograph of the moving object. They can easily visualize their distance from the sonic ranger and how that distance is changing

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Figure 1. The pretest results for questions 1 and 2 (correct answers are underlined).

1. Which distance graph is that of an object moving in a direction away from the origin with a steady (constant velocity?

2. Which distance graph is that of an object standing still?

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over a certain time interval. When students read a distance from the sonic ranger on the graph, they can immediately look and measure the distance with a ruler. Distance from

an object is easily experienced and manipulated, and it is easy for preservice teachers to understand the real-time response of the curve on a graph.

82 Joumal of Science Teacher Education • Spring 1995

Velocity-Time Graphs

Four velocity-time questions were common to both tests. A comparison ofpre- and posttest responses indicated that the preserviee elementary teachers showed great improvement in understanding velocity-time graphs. Figure 2 is typical of a velocity question. On the pretest, the response rate for the correct answer was low (8 of 106; 8%). The posttest demonstrated greater student understanding as suggested by 82 of 106 (77%) students responding correctly.

Interestingly, on the pretest, the preservice teachers chose, in significant numbers, an alternative graph, which would have been the correct choice if the graph were distance-time instead of velocity-time. Of the 106 respondents on the pretest, 77 (73%) selected the answer which corresponds to the distance-analog. After instruction, 57 of the students who selected the distance- analog selected the correct answer. The number of students who continued to select the distance-analog was 14, demonstrating that some students did not change some of their original conceptions for this type of motion. The eight students who did select the correct answer on the pretest also selected the same answer on the posttest suggesting their selection was not a random guess but an educated choice. A few students (less than 5) chose graph C, which suggests that these students may have committed a common sign error.

Distance-Time and Velocity-Time Graphs

To test whether students could utilize a distance-time graph to understand velocity, a distance-time graph with the plot of two separate cars was presented, along with three questions conceming the relationship between the velocities of the two cars. Three response options were presented for each item corresponding to three locations on the graph, with the fourth option being "none of the above."

Students demonstrated no gain in perform ance between the pre- and posttest with regard to these three items. Figure 3 presents data typical of all three questions. Approximately the same frequency of students, 37% (40 of 107), chose the correct answer on the pre- and posttest, but of those selecting the correct response, only about half chose the correct answer on both tests. The responses to the other two questions seemed to indicate an inability to interpret the slope of the line as an indicator of velocity.

The question in Figure 3 is an interesting problem in

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Journal of Science Teacher Education • Spring 1995

which students again seemed to improperly apply position criteria to velocity questions. On the pretest, 58% (61 of 106) of the students chose location B, suggesting students assume that when the position of the cars was the same, the velocities were the same. On the posttest, 40 of the 61 students did not change this choice, showing the strength of their personal construction.

These data suggest little conceptual gain in preservice teachers' knowledge of interpreting velocity from distance- time graphs. While the posttest evidence suggests that improper application of position criteria appears to persist even after instruction, student responses on the course exams and final exam suggested the students knew the subject. The course exam questions only had one curve per graph. Two curves that intersect on a single graph may be what caused the students difficulty. The inconsistency between the course exams and posttest results may be an indication that the students made some conceptual change, but that it still needs further development. Apparently the labs did not provide enough of a challenge to change students' beliefs enough that they could adapt to a new situation.

Acceleration-Time Graphs

Five test questions involved acceleration-time graphs. As with the velocity-time and distance-time graphs, students generally answered all the acceleration-time graph questions in a similar manner. On all questions, very few students (less than 10%) responded correctly to each item on the pretest; however, students showed overall improvement on the posttest with regard to their understanding of acceleration. The responses indicated that 38% (40 of 105) of the students responded to the acceleration questions correctly. Figure 4 presents a question in which a car is moving away from the origin at a constant velocity.

As with the velocity-time graph questions in which students select a distance-analog, they selected avelocity- analog with the acceleration-time graphs questions. The velocity-analog is the correct response to the acceleration question if the graph was velocity versus time instead of accelerationversus time. On the pretest, 61% (62 of 102) of the students selected graph B, which is the velocity- analog to that question. Review of the responses indicated that only 5 of the original 62 students selected their pretest choice, while 31 switched to the correct answer and 21 selected graph D which is the velocity-analog with the opposite sign. For this question, a large number of

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Figure 2. The pretest and posttest results for question 5 (the correct answer is underlined in the matrix).

5. Which velocity graph shows the object moving toward the origin at a steady (constant) velocity?

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84 Joumal of Science Teacher Education • Spring 1995

Figure 3. The pretest and posttest results for question 10 (the correct answer is underlined in the matrix).

Two cars move so that their distance-time graphs are shown below. Choose the time (A, B, or C) when each of the statements is true. You may use a choice more than once or not at all. I f you think none is correct, answer J.

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Joumal of ScienceTeacher Education • Spring 1995 85

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students (36) selected graph D on the posttest. This appeared to be the result of instruction, since on the pretest only two students selected graph D. Apparently instruction did not help the students understand the sign convention. Pretest results showed 24 students selected graph A, which is a distance-analog.

Implications for Instruction

This study supported the use of MBL materials and revised motion curriculum to improve conceptual understanding. The students' gains over a 3-week period for some of the topics were impressive. The MBLs made possible laboratory experiments which were not possible before the introduct ion of computers and, more significantly, the change in philosophy stressing a qualitative understanding of the concepts. Prior to the MBLs, motion was covered in just one 1-I/2 hour lab period and three lectures. The lectures focused on the mathematical derivations of motion, units, and vectors. With the larger range of possible activities with MBLs, it was possible to devote more laboratory time to motion and for the students to explore the concepts in greater depth. The ability to quickly create a graph and experiment is one of the strengths of MBLs. Students started coming to lab to use the computer to complete their homework assignments. MBLs are a valuable tool students can use to bring the abstract concepts of velocity and acceleration within their ability to measure and describe.

The comparison of students' knowledge before and after a set of motion lectures and labs using MBLs suggests that gains in the preservice elementary teachers' knowledge were made, but the degree of success depended upon the specific topic. Pretest results showed students demonstrated a lack of understanding with regard to the differences between position, velocity, and acceleration. The MBL activities helped many students change their conceptions of motion and enabled them to better read and use velocity- time graphs. The ability to gather and display data is a starting point for challenging students' beliefs.

Was there significant conceptual change? In one case conceming the acceleration of a ball at the top of its flight when its velocity was zero, a student asked the instructor if he should answer a question using data on the graph or with the real answer. The student firmly believed the acceleration was zero and did not want to accept the data on the graph. The student was placed in a state of disequilibrium by the data and was trying to resolve the obvious conflict between his belief and the data. This

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Joumal of Science Teacher Education • Spring 1995

student had a learning experience which would not have occurred prior to the introduction of the MBLs. Gains in scores on acceleration and relating two different graphs were not as great as gains in distance-time and velocity- time, but there was change. The students were in a state of disequilibrium. Future MBL activities need to provide more experiences in those areas so that the conceptual change will be more generalized and permanent.

This study suggests a sequence of instruction moving from easier concepts to more difficult concepts. Students found distance-time graphs the easiest to interpret and overcame any misunderstandings with little instruction. Velocity-time graphs were more challenging, but the students were able to quickly m aster these graphs as well. While successful with each type of graph, the students had difficulty relating the two graphs. Students demonstrated this difficulty pre- and post-instruction. Acceleration was even more difficult prior to instruction, but improvements were made after instruction. Students were better able to understand concepts but still needed more experience to be able to better relate those concepts to each other. In order to make conceptual gains in understanding of acceleration and how the concepts of position, velocity, and acceleration are related, more time and lab experiences need to be devoted to acceleration graphs and the relationship between distance-, velocity-, and acceleration-time graphs.

Using MBLs may have improved the students' ability to learn motion concepts; therefore, the MBLs might be employed to a greater degree during instruction in other physical concepts. Temperature, light meters, pressure, pH, force, and numerous other probes for gathering data are available and can be used to teach physical science concepts. Familiarity with the computer and the presentation of data will allow students to focus on the concepts and not on learning how to operate another new instrument. MBLs lend themselves naturally to the use of force probes to explore Newton's Laws and work.

MBLs were a great facilitator for developing a new motion curriculum. The MBLs' flexibility provided many potential activities without additional instruments or expense. Using graphs to represent motion provided data that the students were capable and comfortable using and interpreting. The graphs were something everyone was familiar with and capable of reading. The variety and abundance of data made possible numerous activities at a variety of levels. These activities, combined with increased opportunities for discussion and interpretation, increased the exposure the students had to the content.

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With increased exposure to the content comes more opportunity for conceptual change and meaningful learning.

ConcLusion

Preservice elementary teachers demonstrated the ability to read and interpret distance-lime graphs before instruction. Posttest results suggested the new motion curriculum materials greatly improved students' abilities to read and interpret velocity-time graphs. Despite conducting only one activity with acceleration, students also showed improvement with acceleration-time graphs. The instruction, which included MBL activities, improved the preservice teachers' general conceptual understanding of these kinematic topics. Future research might include a means to better measure the cause for the conceptual change. Multiple factors played a role, including positive student attitudes toward using the computers, ability to make abstract concepts measurable and describable, and opportunities for frequent experimentation.

The capabilities of MBLs changed the focus of the motion curriculum. An MBL's capacity to quickly gather data and display it opens the door for a rich variety of activities. Developing new motion curriculum was enhanced with opportunities for experimentation and exploration made possible by this technology. The revision of the curriculum was rewarding and exciting for both the instructors and students. The students learned the content, saw an appropriate use of technology, and enjoyed using the computer. The instructors enjoyed exploring the topics u sing MBLs and became excited with the possibilities of further usage of MBLs. Using MBLs as the powerful tool they are, motion curriculum will continue to be revised, and the instructors will explore more effective ways of structuring the lessons with ways to better teach.

References

Barrow, W. H. (1990). The effects of microcomputer- based laboratory exercises on achievement and attitude toward physical science of pre-service middle school teachers. Dissertation Abstracts International, 52, 1702.

Halloun, I. A., & Hestenes, D. (1985). The initial knowledge state of college physics students. American Journal of Physics, 53, 1043-1065.

Peters,P. C. (1982). Evenhonorsstudentshaveconceptual difficulties with physics. AmericanJournalofPhysics, 50(6), 501-508.

Rosenquist, M. L.0 & McDermott, L. C. (1987). A conceptual approach to teaching kinematics. American Journal of Physics, 55(5), 407-415.

Saunders, W.L. (1992). The constructivist perspective: Implications and teaching strategies for science. School Science and Mathematics, 92(3), 136-141.

Sokoloff, D. R., &Thomton, R. K. (1990). Tools for scientific thinking: Motion and force teachers' curriculum guide. Portland, OR: Vernier Software.

Thornton, R. K., & Sokoloff, D. R. (1990). Learning motion using real-time microcomputer-based laboratory tools. American Journal of Physics, 58, 858-867.

Trowbridge, D. E., & McDermott, L. C. (1980). Investigation of student understanding of the concept of velocity in one dimension. American Journal of Physics, 48, 1020-1028.

Trowbridge, D. E., & McDermott, L. C. (1981). Investigation of student understanding of the concept of acceleration in one dimension. American Journal of Physics, 49, 242-253.

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