Letter pubs.acs.org/jchemeduc
Constructing Cost-Effective Crystal Structures with Table Tennis Balls and Tape That Allows Students To Assemble and Model Multiple Unit Cells Catherine Elsworth,* Barbara T. Y. Li, and Abilio Ten Foundation Studies, Pathways School, Trinity College, Royal Parade, Parkville, Victoria 3052, Australia S Supporting Information *
ABSTRACT: In this letter we present an innovative and cost-effective method of constructing crystal structures using Dual Lock fastening adhesive tape with table tennis (ping pong) balls. The use of these fasteners allows the balls to be easily assembled into layers to model various crystal structures and unit cells and then completely disassembled again. We have found that this method allows us to challenge the students in a hands-on activity where they construct the structures from single balls and not preconstructed layers. Furthermore, this method enables students to construct the body centered unit cell which is difficult to do with glue and table tennis balls.
KEYWORDS: High School/Introductory Chemistry, First-Year Undergraduate/General, Inorganic Chemistry, Laboratory Instruction, Hands-On Learning/Manipulatives, Crystals/Crystallography, Metals, Solids, Solid State Chemistry
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We have found that Dual Lock fastening adhesive tapes7 provide a solution and would work well for the construction of unit cells and layers for solid state structures. The principle advantage of this type of fastener is that only one type of strip is used for all the balls and makes the construction of the models very straightforward. Furthermore, the manufacturer of this style of fastening adhesive tape claims it has more holding power than the hook and loop method which potentially leads to more stable structures. Using this new method of connecting the balls we can supply the students with kits which are not preassembled. The students then need to connect the balls to form the models from individual atoms which improves the kinesthetic experience. We have in the past investigated commercially available models to construct all cubic unit cells. However, these kits involve carrying around a number of supports and metal rods8 which is not practical in our situation. Furthermore, these commercially available kits are not cost-effective for the number we need in order for the students to share a kit between two in a classroom setting. The advantage of using the table tennis balls with the Dual Lock adhesive tape is that we were able to prepare a large number of kits that could be easily moved from classroom to classroom. In addition, the students are able to construct a body centered unit cell by having a central table tennis ball with an extra strip of the fastener and a lightweight paper support.9
INTRODUCTION The value of using crystal lattice models in the classroom has been documented previously in this Journal.1−3 The use of table tennis (ping pong) balls to model crystal structures has been shown to be an inexpensive way to give students the kinesthetic experience of constructing crystal structures.4,5 Typically, construction procedures have utilized glue to attach the balls together to form layers which we ourselves have adopted over a number of years. The model kits we provided students included simple cubic and close packed layers, and this required the layers to be constructed prior to the classroom activity. In our experience, we found the use of glue to be tedious in that the layers tended to be fragile, and it was time-consuming to continually repair them. We sought to investigate ways to improve these model kits as well as the learning experience for the students. An article by Sow and co-workers presented the use of tennis balls and perspex boxes for building crystal structures.6 The authors sought student feedback on how to improve the teaching method and one suggestion proposed the possible use of balls made of a hook and loop style fastener. This type of fastener has the advantage of being easily assembled and disassembled for repeated use. We considered using a strip of this type of fastener around the table tennis balls. However, their usage on balls for construction of crystal structures requires the balls to have either a hook or a loop strip, which can be problematic when assembling the layers as they do not always connect correctly. Ideally construction would be simpler if all the strips on the balls were the same. © XXXX American Chemical Society and Division of Chemical Education, Inc.
Received: May 5, 2017
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DOI: 10.1021/acs.jchemed.7b00305 J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
Letter
Figure 1. Space-filling models of (a) simple cubic unit cell and (b) cubic close packed unit cell. (c) The first and second layers of the body centred cubic unit cell.
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CONSTRUCTION OF LAYERS AND UNIT CELLS FOR CRYSTAL STRUCTURES The table tennis balls we used are standard 40 mm diameter balls. A 5 mm thick strip of the Dual Lock fastener is attached along the perimeter of each ball (12.57 cm), and this allows for the construction of both the simple cubic and face centered cubic unit cells as shown in Figure 1a,b. We supply the students with kits containing 16 orange balls and 32 white balls to allow students to construct three close packed layers and to investigate the difference between cubic and hexagonal close packings. Our classroom sizes consist of approximately 14 students using 7 kits in groups of 2. The use of different colored balls enables the students to construct contrasting layers to better visualize the stacking sequence. By providing an extra table tennis ball with an additional strip of Dual Lock fastener placed perpendicular to the first one, it is possible for the students to construct the body centered cubic unit cell. The first and second layers are shown in Figure 1c. For convenience the body centered cubic unit cell can be constructed by using an origami box9 with a square base (8.62 cm) as a guide. The assembly instructions for each of these unit cells and the closed packed layers in the ccp and hcp structures are provided in the Supporting Information.
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors wish to thank Lucia Jurdana for help with construction of the model kits; Mei Fong, Kerry Higgins, Steven Ng, and Shan Sun who trialed the kits; and our students who have been enthusiastic participants in our classes.
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REFERENCES
(1) Ohashi, A. Using Latex Balls and Acrylic Resin Plates to Investigate the Stacking Arrangement and Packing Efficiency of Metal Crystals. J. Chem. Educ. 2015, 92, 512−516 and references cited therein.. (2) Sunderland, D. Studying Crystal Structures through the Use of Solid-State Model Kits. J. Chem. Educ. 2014, 91, 432−436. (3) Scattergood, A. The Making of Crystal Lattice and Unit Cell Models. J. Chem. Educ. 1937, 14, 140. (4) Hatch, R. A.; Comeforo, J. E.; Pace, N. A. Transparent, Plasticball Crystal Structure Models. Am. Mineral. 1952, 37, 58−67. (5) Sands, D. E. Introduction to Crystallography; Dover Publications: New York, 1993. (6) Sow, C. H.; Udalagama, C. N. B.; Lim, G. Q. Teaching Crystal Structures Using a Transparent Box with Tennis Balls. Journal of the NUS Teaching Academy 2013, 3, 18−33. (7) The mushroom style fastening adhesive tapes used were Scotch Outdoor Fasteners RF5761, 1 in × 15 ft (25.4 mm × 4.57 m). They were cut into 5 mm wide strips with a length of 12.57 cm. (8) Solid-State Model Kit produced by Institute for Chemical Education; University of WisconsinMadison. For more information: http://ice. chem.wisc.edu/Catalog/SciKits.html (accessed May 2017). (9) A four modular origami box designed by Tomoko Fuse was constructed from square pieces of paper (16.25 cm). Instructions can be found at: http://www.origami-instructions.com/modular-squarebox-p1.html (accessed May 2016).
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CONCLUSION The use of the kits has been found to be a valuable and inexpensive way for our students to gain the kinesthetic experience of constructing unit cells of crystal structures. In our classes, we have noticed significant improvement in the way students are able to determine the cell contents of unit cells and locate the position of octahedral and tetrahedral holes between close packed layers. It is also possible to explore the use of these kits to build other solid state structures than those mentioned in this letter. To demonstrate the versatility of the kit we have also used the kits to construct models of the rhombohedral unit cell as well as graphene as demonstrated in the Supporting Information.
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AUTHOR INFORMATION
Corresponding Author
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.7b00305. Instructions for putting together the models of the simple cubic, body centered cubic, cubic close packed, and hexagonal close packed structures (PDF) B
DOI: 10.1021/acs.jchemed.7b00305 J. Chem. Educ. XXXX, XXX, XXX−XXX
