Computer Animation & Diffusion.pdf

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Can Computer Animations Affect College Biology Students' Conceptions about Diffusion & Osmosis? Author(s): Michael J. Sanger, Dorothy M. Brecheisen, Brian M. Hynek Source: The American Biology Teacher, Vol. 63, No. 2 (Feb., 2001), pp. 104-109 Published by: University of California Press on behalf of the National Association of Biology Teachers Stable URL: http://www.jstor.org/stable/4451051 . Accessed: 05/05/2011 00:02 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=ucal. . Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. University of California Press and National Association of Biology Teachers are collaborating with JSTOR to digitize, preserve and extend access to The American Biology Teacher. http://www.jstor.org

Transcript of Computer Animation & Diffusion.pdf

  • Can Computer Animations Affect College Biology Students' Conceptions about Diffusion &Osmosis?Author(s): Michael J. Sanger, Dorothy M. Brecheisen, Brian M. HynekSource: The American Biology Teacher, Vol. 63, No. 2 (Feb., 2001), pp. 104-109Published by: University of California Press on behalf of the National Association of Biology TeachersStable URL: http://www.jstor.org/stable/4451051 .Accessed: 05/05/2011 00:02

    Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unlessyou have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and youmay use content in the JSTOR archive only for your personal, non-commercial use.

    Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at .http://www.jstor.org/action/showPublisher?publisherCode=ucal. .

    Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printedpage of such transmission.

    JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

    University of California Press and National Association of Biology Teachers are collaborating with JSTOR todigitize, preserve and extend access to The American Biology Teacher.

    http://www.jstor.org

  • Can Computer Animations Affect College Biology Smdents' Conceptions About

    Diffusion & Osmosis? Michael J. Sanger Dorothy M. Brecheisen Brian M. Hynek

    T HE concepts of diffusion and osmosis are very important for biology students to understand. Diffusion is the primary method of short-dis-

    tance transport in cells and cellular systems. Osmosis is used to explain water uptake by plants, turgor pressure in plants, water balance in aquatic creatures, and transport in living organisms (Odom 1995). Unfortunately, students find these topics very difficult to understand (Friedler, Amir & Tamir 1987) and several biology education researchers have reported student misconceptions associated with these topics (Marek 1986; Zuckerman 1994; Odom & Barrow 1995). One reason why students may have difficulty with the concepts of diffusion and osmosis is because these concepts require students to visualize and think about chemical processes at the molecular level (John- stone & Mahmoud 1980; Friedler, Amir & Tamir 1987; Westbrook & Marek 1991).

    A decade ago, Nurrenbern and Pickering (1987) discovered that students who are successful in solving numerical chemistry problems did not necessarily understand the molecular concepts underlying these problems. Since that time, others have documented students' difficulties in answering visual conceptual questions based on the particulate nature of matter (Gabel, Samuel & Hunn 1987; Sawrey 1990; Pickering 1990; Nakhleh 1993). Research in this area has demon- strated that instruction involving computer anima- tions can facilitate the development of students' visu- alization skills and their abilities to think about chemi- cal processes at the molecular level (Williamson & Abraham 1995; Russell et al. 1997; Sanger & Green- bowe 1997).

    The purpose of this study was to determine whether viewing computer animations depicting the molecular processes of diffusion and osmosis would

    affect students' conceptions of these topics. Students' conceptions of diffusion and osmosis topics were measured using the Diffusion and Osmosis Diagnostic Test (Odom 1995; Odom & Barrow 1995).

    Methods This study was performed using 149 students

    enrolled in a second-semester introductory college biology course at a small Midwestern university. These students are predominantly first-year biology majors who were also enrolled in a second-semester introductory college chemistry course. All of these students attended the same lecture section which met for three hours per week and was taught by a college biology instructor who has taught this class three times a year for 12 years. Each student was also enrolled in one of six different laboratory sections containing 21 to 28 students who were taught by a college biology instructor or a graduate student.

    This research study was performed in the labora- tory sections after the students had received instruc- tion on diffusion and osmosis in the lecture section. The laboratory sections were randomly assigned to either the control or experimental group. Students in the experimental group received instruction using two computer animations to explain the molecular behaviors associated with the processes of diffusion. Both groups performed several experiments including the diffusion of potassium permanganate in water, the osmosis of water and glucose (but not starch) through cellulose dialysis tubing, and the effect on the cells of an Elodea leaf after being placed in hypotonic, isotonic and hypertonic solutions. The major difference between the two groups is that the experimental group viewed two animations before performing these experiments while the control group did not.

    The first animation depicted the molecular pro- cesses occurring when perfume particles diffuse through the air (Figure 1). The perfume particles were represented as pink circles (since the perfume molecules would be very complex) and air was repre- sented as N2 and 02 molecules. As the animation

    Michael J. Sanger is an Assistant Professor of Chemistry and Science Education and Dorothy M. Brecheisen is an Instruc- tor of Biology at the University of Northern Iowa, Cedar Falls, IA 50614-0423. Brian M. Hynek was an undergraduate earth science and all sciences teaching major at the University of Northern Iowa and is now a graduate student in Earth and Planetary Sciences at Washington University, One Brookings Drive, St. Louis, MO 63130-4899.

    104 THE AMERICAN BIOLOGY TEACHER, VOLUME 63, NO. 2, FEBRUARY 2001

  • U S

    FS 0

    Figure 1. Computer screen image of the diffusion of perfume molecules (circles) in air.

    proceeds, the perfume particles and the air molecules collide with themselves and with each other until all of the particles are evenly distributed throughout the screen. Students in the experimental group viewed this animation three times while the first author narrated the action appearing on the screen, empha- sizing that the random motion and collisions of these particles leads to this even distribution. This description of the movement of perfume molecules in a room is simplistic and ignores other mixing processes (such as convection currents). However, it does correctly demonstrate that all gaseous molecules are in constant motion and, in the absence of convec- tion currents or other forces, these molecules will slowly mix via diffusion.

    The second animation starts with a drawing of a thistle tube experiment that the students had seen and discussed in lecture (Zuckerman 1994, 1995). It starts with a thistle tube covered by a semi-permeable membrane and filled with Karo? syrup that has been placed in a beaker of water. As the process of osmosis occurs, the Karo? syrup level in the thistle slowly

    rises and eventually levels out. The animation also depicts the molecular processes occurring in this experiment (Figure 2). The semi-permeable membrane is represented as a dashed line that separates the Karo? syrup solution on top from the water on bottom. The syrup particles are represented as brown circles for simplicity and the Karo? syrup solution contains both syrup particles and H20 molecules. The holes in the semi-permeable membrane were made large enough for the water molecules to pass through but small enough so that the sugar particles cannot pass through them.

    Students in the experimental group viewed the molecular portion of the second animation three times. The first time, the students were simply directed to watch the animation. These students were asked which particles could travel through the mem- brane and why and in what direction these particles moved. In each section, the students replied that water molecules could travel through the barrier but the syrup particles could not due to size effects, and that the water molecules traveled in both directions

    DIFFUSION & OSMOSIS ANIMATION 105

  • \~~ -- N

    Figure 2. Computer screen image of the osmosis of water molecules through a semi-permeable membrane between pure water and a syrup solution.

    but more water molecules moved from the pure water into the syrup solution. The students viewed the animation again, with half of the class counting the number of water molecules entering the syrup solution and the other half counting the number of water molecules entering the water solution. The students reported that there were nine water mole- cules entering the syrup solution throughout the animation and four molecules entering the water solution, predominantly at the end of the animation. The students were then allowed to watch the anima- tion one more time.

    After performing the laboratory experiments men- tioned above, both sets of students were asked to respond to the Diffusion and Osmosis Diagnostic Test (DODT). The DODT consists of 12 two-tier multiple choice questions. The first-tier responses are based on content questions, while the second-tier responses ask students to explain their choices in the first tier. The responses in the second tier are based on misconceptions identified by student responses to these questions and student interviews.

    To determine the effects of viewing the computer animations, responses to the questions on the DODT were compared from students who viewed the anima- tions and from those who did not.

    Results & Discussion Odom (1995) reported a list of student misconcep-

    tions he identified using the DODT. The number and percentage of the students choosing responses consistent with these misconceptions were tabulated for the control and experimental groups, and these numbers were checked for statistically significant differences. Table 1 contains a list of misconceptions for which we found significant differences.

    The most striking difference is that students who viewed the animations were less likely to choose responses suggesting that particle motion stops after equilibrium is reached (Misconceptions 1 and 2). While 8% of the students in the control group believed that dye and water molecules stop moving once they are mixed because otherwise the container would be

    106 THE AMERICAN BIOLOGY TEACHER, VOLUME 63, NO. 2, FEBRUARY 2001

  • Table 1. Number (percentage) of student responses consistent with misconceptions measured by the Diffusion and Osmosis Diagnostic Test.

    Misconceptions Control a Experimentalb

    1. When a drop of blue dye is placed in a container of clear water, the dye molecules 6 (8) 0 (0) stop; otherwise the container would be different shades of blue.

    2. Particles move from high to low concentration because they tend to move until the two 27 (36) 14 (19) areas are isotonic and then the particles stop moving.

    3.- When a drop of dye is placed in a container of clear water, the dye molecules continue 2 (3) 10 (14) to move around because if they stopped, they would settle to the bottom of the container.

    4. As the difference in concentration increases between two areas, the rate of diffusion 36 (47) 23 (32) increases because the molecules want to spread out.

    5. When sugar is added to water, after a very long time the sugar will be more 2 (3) 8 (11) concentrated on the bottom of the container because sugar dissolves poorly or not at all in water.

    aN = 76 students bN = 73 students

    different shades of blue, none of the students who viewed the animation chose this response (z = - 2.45, p = .014). Similarly, more students in the control group believed that particles move until they are isotonic and then stop moving than in the experimen- tal group (36% versus 19%), z = -2.23 and p = .026. In general, it appears that these animations were successful in helping students understand the dynamic nature of equilibrium processes, which is a common and persistent misconception exhibited by students in chemistry classes as well (Gorodetsky & Gussarsky 1986).

    Although the students who viewed the animations were less likely to believe that the particles stop moving once they reach equilibrium, they were more likely to exhibit a misconception about why these particles do not stop moving (Misconception 3). While only 3% of the students in the control group believed that dye and water molecules keep moving once they are mixed because otherwise they would settle to the bottom of the container, 14% of the students in the experimental group chose this response (z = 2.49, p = .013). It appears that although the anima- tions convinced students that the particles do not stop moving once they reach equilibrium, it was not completely effective at convincing them why they don't stop moving (random motion).

    On the other hand, students who viewed the anima- tions were less likely to attribute molecular motions to anthropomorphic "desires" of the molecules (Mis- conception 4). More students in the control group believed that as the difference in concentration increases between two areas, the rate of diffusion increases because the molecules want to spread out than in the experimental group (47% versus 32%), z = - 1.98 and p = .048. Both Zuckerman (1994) and Odom and Barrow (1995) cited the importance of understanding the concept of osmosis as the result of random molecular motions, and claimed that stu-

    dents agreeing with the statement above attribute these motions not to random collisions but to the wants or desires of the molecules.

    Although the animations had a positive effect on students' conceptions about the particulate nature and random motion of matter, the animation appeared to convince students that sugar does not dissolve in water (Misconception 5). While only 3% of the students in the control group believed that sugar does not dissolve well in water, 11% of the students who viewed the animations chose this response (z = 2.05, p = .040). Discussions with students revealed that they interpreted the brown circles surrounded with water molecules in the second animation (Figure 2) as suggesting that the sugar and water particles did not completely mix with each other and that these sugar particles did not dissolve in water. This diffi- culty stems from students trying to apply rules that work at the macroscopic level, like "if you can see

    Science Item Writers - The General Educational Development Testing Service (GEDTS) is recruit- ing science teachers to prepare brief passages in- cluding graphics and multiple-choice test items for the new GED 2002 Series Science Test. The GED Tests measure the major academic skills and know- ledge associated with a four year high school pro- gram of study. Please send your name, address, phone number, and resume to: David Kuhn, GEDTS, One Dupont Circle, NW Suite 250, Washington, DC 20036-1163: (office) (202) 939-9494; (E-mail) david [email protected]; (Fax) (202) 939-8578.

    DIFFUSION & OSMOSIS ANIMATION 107

  • the particles, the compound has not dissolved in water," to pictures at the molecular level (Sanger 1999).

    Implications for the Classroom This study demonstrates that students who viewed

    computer animations depicting the molecular pro- cesses occurring when perfume particles diffuse in air and when water osmoses through a semi-permeable membrane developed more accurate conceptions of these processes based on the particulate nature and random motion of matter (Misconception 4). They also had a better conceptual understanding of the dynamic processes occurring in equilibria reactions (Misconcep- tions 1 and 2). For the past decade or so, chemical education researchers have stressed the importance of asking students to think about chemistry concepts at the particulate level (Nurrenbern & Pickering 1987; Gabel, Samuel & Hunn 1987; Sawrey 1990; Pickering 1990; Nakhleh 1993) and the evidence suggests that when students receive chemistry instruction including particulate drawings, they are better able to answer conceptual questions that are based on the particulate nature of matter (Williamson & Abraham 1995; Rus- sell et al. 1997; Sanger & Greenbowe 1997). These results suggest that instruction including computer

    animations at the particulate level can help students understand chemistry and biology concepts involving molecular processes. Some of these biology concepts include Brownian motion, diffusion, osmosis, 3D structure of DNA, cellular transport mechanisms (membrane structure, passive and active transport, etc.), and enzyme-substrate complexes.

    Many newer versions of college biology textbooks are packaged with a CD-ROM containing instruc- tional resources, including computer animations of molecular processes (Krogh 2000; Raven & Johnson 1999). High school biology textbooks, on the other hand, tend to come with many ancillary materials for the instructor such as CD-ROMs, videotapes, laserdiscs, or web site addresses, and these materials also contain computer animations of biology concepts at the particulate level (Miller & Levine 1998; Strauss & Lisowski 1998). Although the use of particulate drawings is being promoted by science education researchers, instructors who choose to use them in their instruction need to be made aware of the results of this research and what it can tell them about student learning in the classroom. Educational psy- chology research performed by Mayer and coworkers (Mayer & Gallini 1990; Mayer & Anderson 1991, 1992) suggests that instruction using computer anima- tions is most effective when the words and pictures are presented simultaneously, rather than separated from one another in time or space. Greenbowe et al. (1995) reported that in order for students to have enough time to interpret the particulate drawings included in computer animations, these animations should be shown successively at least three times (with narration) to the students. They also reported that students' abilities to interpret particulate draw- ings in computer animations greatly improve as their exposure to these drawings and animations increases.

    Unfortunately, instructors who choose to incorpo- rate computer animations and particulate drawings in their instruction and assessment may encounter difficulties. It can be very difficult for instructors to create particulate drawings that faithfully represent the scientific phenomena and that test the concepts of interest (Sanger & Greenbowe 2000). Another problem instructors may face is that because students are unfamiliar with particulate drawings, they may misin- terpret these drawings. For example, students in this study misinterpreted the drawings in the computer animation depicting the osmosis of water through a semi-permeable membrane into a syrup solution (Fig- ure 2) as suggesting that sugar particles do not dissolve in water. In this case, the students tried to interpret the molecular pictures using macroscopic observations or definitions (Sanger 2000). Ulti- mately, each instructor has to decide whether the additional information that can be presented using particulate drawings and computer animations

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  • warrants the possible difficulties associated with using these drawings and animations.

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    DIFFUSION & OSMOSIS ANIMATION 109

    Article Contentsp. 104p. 105p. 106p. 107p. 108p. 109

    Issue Table of ContentsThe American Biology Teacher, Vol. 63, No. 2 (Feb., 2001), pp. 81-144Front Matter [pp. 81-103]Guest EditorialWe Teach Biology Backwards [p. 82]

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