Fall 2009 CONFCHEM |
Excellence in Education with CCLI: Notes from Recent AwardeesAn on-line conference, September and October 2009 |
|||
| Abstracts | Papers | Instructions | Discussion Archive | |
Fall 2009 CONFCHEM |
Excellence in Education with CCLI: Notes from Recent AwardeesAn on-line conference, September and October 2009 |
|||
| Abstracts | Papers | Instructions | Discussion Archive | |
Dean H. Johnston
Department of Chemistry and Biochemistry
Otterbein College
Westerville, OH 43081
djohnston@otterbein.edu
A variety of web-based materials for teaching concepts of point group symmetry have been developed using the Jmol applet. Example molecules are displayed as three-dimensional structures combined with the interactive display of symmetry elements as translucent points, axes and planes. Symmetry operations are demonstrated through animations. Along with this development, we have undertaken a study to compare the relative effectiveness of two-dimensional (2D) versus three-dimensional (3D) computer representations for teaching concepts of symmetry. Two groups of first and second-year undergraduate students with no formal instruction in concepts of symmetry completed a 2D and a 3D version of an online symmetry tutorial in random order and were assessed with a 20-question quiz after completion of each tutorial. Preliminary analysis shows significant score gains with both tutorials, strong interactions between mental rotation scores and pre/post-test gains, and an intriguing advantage for the non-interactive (2D) tutorial.
The ability to present chemical structures in complex three-dimensional representations has the potential to both educate and overwhelm our students. Teachers and textbooks can now create visually appealing representations without ensuring that students are able to accurately interpret these pictures. Research has clearly shown, however, that properly designed computer representations and animations can help students see the relationships between different representations and the macroscopic properties of materials [1-12]. For example, computer visualization has been shown to help students better understand the particulate nature of matter [1], the basis of diffusion and osmosis [5], and the relationship between chemical structure and polarity and miscibility [4]. Several studies have explored the effectiveness of computers for teaching visual-spatial skills in Chemistry [13-15]. Copolo and Hounshell found that computer modeling enhanced retention when learning organic structures and isomers [13]. More notably, Barnea and Dori showed that a computer-based learning environment enhanced the spatial abilities of high-school chemistry students [14].
Mathewson has identified a large number of visual-spatial themes or "master images" that connect various fields of science [16]. Mathewson suggests that these images can be used as focal points in developing new curricula. Symmetry, a topic grounded in mathematics, but with numerous applications in physics, chemistry and biology, is an appealing master image because of its visual connection to both science and art. The strong visual-spatial component of symmetry makes it an ideal test case for developing and assessing the effectiveness of computer-generated visual teaching materials.
This NSF-CCLI project (NSF-DUE #0536710) seeks to develop a web-based cross-platform resource for teaching point group symmetry and to assess the effectiveness of three-dimensional computer models for teaching concepts of symmetry to undergraduate students.
The Symmetry@Otterbein web site (http://symmetry.otterbein.edu) was constructed with a clear set of design principles to maximize its usefulness and accessibility.
Interactivity Research has shown that students are better able to visualize three-dimensional structures when they are able to manipulate the model themselves [17]. Animations of static structures without the ability to interact and explore appear to be less effective and do not encourage further exploration [18]. This project developed a web site where students are able to individualize how they want to look at each example, potentially allowing them to find the "Oh, I see it now!" angle that jumps out for them.
Value-added The indiscriminant application of new technologies to education can obscure learning objectives. The use of computers to generate molecular displays for their own sake may in some cases be less effective than the use of physical models due to the lack of visual depth cues in the two-dimensional display. A major goal of this tutorial is to display and animate aspects of symmetry elements and operations that cannot be achieved using physical models as discussed in the next objective.
Animation The animation of symmetry operations is particularly effective in demonstrating what is meant by inversion through an inversion center or reflection through a plane. The computer can demonstrate these concepts in ways that are physically impossible with hand-held models. Similarly, using computer graphics to interactively display symmetry elements such as axes and planes that pass through bonds and atoms overcomes the limitations of fixed two-dimensional diagrams or physical models. Thus computer visualization is a powerful tool when exploring these topics.
Accessibility Computer visualization is not a method to replace more conventional teaching methods, but rather a technique that can enhance traditional model kits, lectures, discussions and demonstrations [4]. This web site is designed to be used as both a visual introduction to point group symmetry in lecture and as a reference that students can come back to when doing homework assignments. The site as a freely available, web-accessible, cross-platform compatible (Java-based) tool, thereby removing potential barriers. The universal availability of the web will promote more effective learning by encouraging many short exposures to the material [4, 18], rather than one extended use.
The Symmetry@Otterbein web site currently contains three basic modules - a Symmetry Tutorial, the Symmetry Gallery and the Symmetry Challenge. The Symmetry Tutorial reviews the basic symmetry elements and operations with several example molecules on each page. Each element can be selectively displayed, and each operation can be animated by pressing the appropriate button.
Figure 1. A view of the Symmetry Tutorial showing the different proper rotation axes present in ethane in the staggered configuration.
The Symmetry Gallery brings the same type of interactive display found in the Symmetry Tutorial to a collection of over seventy molecules and shapes. Links are included to the literature (as DOI and WebCSD links) for crystallographically determined structures.
Figure 2. A view of the Symmetry Gallery showing the two mirror planes present in one configuration of the tetrabromoneopentane molecule.
The Symmetry Challenge guides students through a detailed point group determination flow chart for any of the over seventy example structures. The flow chart provides visual feedback at each stages, highlighting the presence of each symmetry element.
Figure 3. A view of the Symmetry Challenge in the process of determining the point group of the octachlorodiosmate(III) anion.
Origins These materials were originally created for a sophmore-junior level Inorganic Chemistry course at Otterbein College. An initial version of the tutorial was originally created using the Chime plug-in. Due to the lack of cross-platform capability for Chime and the rapid development of the Jmol applet, development of Jmol-based materials begin in 2006. All current development is exclusively with Jmol [19].
Web Content and HTML HTML pages and accompanying Javascript code were created using Dreamweaver. Graphics were created using Photoshop and Jmol. Molecular structures were either constructed using HyperChem or retrieved from the Cambridge Structural Database [20]. Some structure clean up and symmetrization was performed with Schrödinger Maestro 8.5.
Structure files All structures are stored as JSON (Javascript object notation) files. JSON is a lightweight data format [21] that allows storage of atomic coordinates, bonds, and symmetry information in a single file. An example JSON file for water is shown below:
{
"name":"water",
"pointGroup":"C<sub>2v</sub>",
"atomArray":[
{ "element":"O", "x":0.00000, "y": 0.00000, "z": 0.36960 },
{ "element":"H", "x":0.00000, "y":-0.78385, "z":-0.18480 },
{ "element":"H", "x":0.00000, "y": 0.78385, "z":-0.18480 } ],
"bondArray":[
{ "a1":1, "a2":2, "type": "SINGLE" },
{ "a1":1, "a2":3, "type": "SINGLE" } ],
"faceArray":[ ],
"inversionCenter": null,
"properArray":[
{ "order":2, "direction": { "x":0, "y":0, "z":1 }} ],
"improperArray":[ ],
"reflectionArray":[
{ "direction": { "x":0, "y":1, "z":0 }, "label": "xz" },
{ "direction": { "x":-1, "y":0, "z":0 }, "label": "yz" } ]
}
By using JSON files, the Javascript code can use "AJAX"-style methods to retrieve the information from the server and then feed the necessary structural information to Jmol via Jmol's inline data command. The JSON files are evaluated using the evalJSON command within the Prototype Javascript framework.
Animations and symmetry element display Animations are created "on-the-fly", again using the Jmol inline data command, appending each new animation to the current structure as a new set of models. Rotation axes and reflection planes are drawn using the Jmol draw FIXED command, ensuring that they are displayed even during animations.
Javascript specifics A number of outside resources and libraries have been used in the development of this web site. The most significant are listed below:
A study was designed to compare the relative effectiveness of non-interactive/two-dimensional (2D) versus interactive/three-dimensional (3D) computer representations for teaching concepts of symmetry. The study was set up using a simple "crossover" design. The participants were divided into two balanced groups based on their scores on a mental rotation test (Purdue ROT), performance on previous chemistry examinations, and gender. Two online tutorials covering basic concepts of molecular symmetry were set up. One tutorial contained interactive three-dimensional (hereafter 3D) structures while the second contained non-interactive static images (hereafter 2D) as shown in Figure 4.
Figure 4. Screenshots of the two different tutorials. On the left is the static, non-interactive version. On the right is the interactive version shown in the process of animating a rotation about a C3 axis in methane.
A total of 120 undergraduate students at two different universities (Otterbein College and Southern Illinois University Edwardsville) with no formal instruction in concepts of symmetry completed the 2D and 3D tutorials in random order and were assessed with a 20-question quiz (see Figure 5) after completion of each tutorial. For the following text and figures, "Group A" refers to the group that saw the tutorials in the 3D/2D order; "Group B" saw the same two tutorials in the reverse order (2D/3D).
Figure 5. Three example questions from the 20-question pre/post-tests.
The schedule of testing and other activities is outlined below:
Student Feedback Fifty percent of the students indicated that they felt the 3D tutorial was more effective with comments that it was "very helpful" and they "liked being able to rotate the molecules". Fourteen percent preferred the 2D tutorial and thirty-six percent had no preference.
Results The results, in the form of average percent improvement following each tutorial, are shown in Figures 6 and 7.
Figure 6. Total improvement was independent of treatment order for both groups for the study with students at Otterbein College (Ntotal = 37).
Figure 7. Total improvement was independent of treatment order for both groups for the study with students at Southern Illinois University Edwardsville (Ntotal = 83).
The results were remarkably consistent between the two studies in spite of being rather different populations. The sample of students at Otterbein College was gender balanced (19 women and 18 men) and consisted of mostly Biology and Chemistry majors. The students at Southern Illinois University Edwardsville, while also in a General Chemistry course, were primarily engineering majors and overwhelmingly (>95%) male. Preliminary statistical analysis shows that the total improvement was independent of the assigned group. In other words, students appeared to learn about the same amount regardless of whether they saw the 2D or 3D version first.
Contrary to expectations and most student opinions, the non-interactive (2D) version consistently led to greater score improvement. Due to the relatively small sample size and large variance in scores, this effect appears to be significant at the 95% level only if (1) you combine the results from the two studies, or (2) you ignore the order of the treatments. The fact that the total improvements observed did not depend on the order of treatment lends some validity to the second procedure.
The advantage we observed for the two-dimensional presentation seems to contradict the conclusions of two recent studies [10, 26]. However these studies differed from the current study in several ways. Limniou, et al. were comparing an immersive virtual reality environment to a more conventional "flat" presentation of the animations, while Wang et al. investigated the influence of 2D versus 3D presentations on the spatial visualization skills of students. A study by Urhahne, et al. investigated the effectiveness of three-dimensional computer simulations in helping students understand chemical structures and their properties [12]. They found that computer simulations were only effective with younger students with less experience in different visual representations.
While the results are initially non-intuitive, they may lead to insights about how students construct an understanding of symmetry and symmetry operations. Perhaps the lack of an interactive/animated model forces the student to create a mental picture of the symmetry element or operation, thereby enhancing their ability to visualize elements and operations on later quizzes. In other words, the computer-generated 3D model may allow the student do less work by creating the image for them. Another related explanation could be that the interactive animation may distract students from the task at hand, leading to less learning. Two recently publications [27, 28] describe tools for teaching symmetry allow students to arbitrarily define symmetry elements and explore the results of apply a particular operation. This open-ended exploration, while potentially tedious for the student, will require a higher degree of mental engagement and almost certainly will lead to a greater understanding.
It should be kept in mind that both versions teach concepts of symmetry effectively. It could be argued that the combination of 2D and 3D tutorials may be more effective than either one alone, though the current study was not designed to address this possibility. This work also did not attempt to investigate the incorporation of physical models and several papers have shown the effectiveness of using a combination of physical and virtual models [11, 29]. Further studies may be able to delineate the significance of each of these types of molecular representations in the process of constructing students' understanding of molecular structure and symmetry.
Thanks to the National Science Foundation for funding (DUE #0536710), Eric J. Voss for his assistance with the collection of experimental data, and to the students at Otterbein College and Southern Illinois University Edwardsville for their participation.