Prediction! The VSEPR Game: Using Cards and Molecular Model

Mar 30, 2018 - Previous work has shown that the formation of misconceptions remains one of the most significant barriers to progress for chemistry stu...
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Prediction! The VSEPR Game: Using Cards and Molecular Model Building To Actively Enhance Students’ Understanding of Molecular Geometry Erlina,*,†,‡ Chris Cane,§ and Dylan P. Williams† †

Department of Chemistry, University of Leicester, LE1 7RH Leicester, United Kingdom Department of Chemistry Education, Faculty of Teacher Training and Education, Tanjungpura University, Pontianak, Indonesia § GENIE CETL, University of Leicester, LE1 7RH Leicester, United Kingdom ‡

S Supporting Information *

ABSTRACT: Previous work has shown that the formation of misconceptions remains one of the most significant barriers to progress for chemistry students. Determination and visualization of the shapes of molecules using valence shell electron pair repulsion theory (VSEPR theory) is an example of an abstract concept that students often find difficult to learn. Concepts may be better understood if the learning process were supported by innovative, interactive, learning resources. In order to address the conceptual difficulties that students may encounter when using VSEPR theory, an activity has been developed that is supported by simple molecular models. Activity cards give students the opportunity to work through the steps required to predict the shape of a molecule in an engaging manner that promotes social learning. Students were tested before and after the activity. A statistically significant improvement in scores (p = 0.001) was found, which indicates that the activity cards and molecular models could help students understand the topic. KEYWORDS: First-Year Undergraduate/General, Interdisciplinary/Multidisciplinary, VSEPR Theory, Humor/Puzzles/Games, Hands-On Learning/Manipulatives, Misconceptions/Discrepant Events, Enrichment/Review Materials

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INTRODUCTION A number of studies have investigated the impact of alternative conceptions (or misconceptions) on student learning in chemistry.1−5 The perceived difficulty of the subject caused by these misconceptions may reduce the interest and enthusiasm of some students for chemistry.6 Students who have these kinds of negative attitude toward the subject may be less engaged and less motivated to study the subject at higher levels.7 The abstract and complex nature of chemical concepts1,8−10 and the inability of students to make a relationship between the three levels of representations in chemistry11 are believed to be the main reasons for students finding the topics difficult. The three levels of representation used in chemistry teaching consist of macroscopic, submicroscopic, and symbolic. These forms of representation (sometimes referred to as the “chemistry triplet”) have been a focus of chemistry education research for decades.3,12 Wu, Krajcik, and Soloway13 explained that the © XXXX American Chemical Society and Division of Chemical Education, Inc.

macroscopic level of representation alludes to phenomena that are observable, for instance, an observation of a change of phase or color change. The submicroscopic level refers to phenomena that occur on the atomic and molecular scale. At this level, the nature of arrangement and movement of molecules is used as a basis for explaining concepts. For example, water is represented as a molecule, consisting of an oxygen atom and two hydrogens atoms (Figure 1). The symbolic level is based on the use of a representation of atoms, molecules, and compounds, such as chemical symbols, formulas, and structures by using letters; for example, water is H2O, and table salt (sodium chloride) is NaCl. As stressed by Dori et al.,14 many teachers do not understand the Received: September 8, 2017 Revised: March 15, 2018

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DOI: 10.1021/acs.jchemed.7b00687 J. Chem. Educ. XXXX, XXX, XXX−XXX

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Figure 2. A set of the activity cards.

Figure 1. Multiple representations in chemistry, using water as an example.

the summary of important definitions, the brief introduction of VSEPR theory, the question cards, the right answer cards, and the wrong answer cards. The activity card consists of questions based on example molecules. Answering the questions allows students to work toward determining the shapes of the molecules. The activity provides students with feedback after answering each question; students who get answers wrong are given hints. As a learning resource, this has been designed to allow future adaptation. Teachers and instructors are free to adapt, change, or add more sample molecules. The activity card is supported by molecular models and a worksheet. The molecular model is used to show students the three-dimensional shape of the molecule, which students have to build by themselves. The model also allows students to develop an appreciation of the effect of a lone pair on the shape of the molecule. A worksheet is provided as a tool to summarize the whole activity. In the worksheet, students should write the steps needed to predict the shape of the molecule based on step-by step questions given in the cards. The worksheet given is a free form; thus, students should write the steps down with their own words.

importance of integrating the three levels of representations of the study, so students have difficulties in learning chemistry. An example of an abstract concept that students often have difficulty with is the determination of molecular geometries using valence shell electron pair repulsion theory (VSEPR theory).15−19 Determining the shape of a molecule is a key skill that all chemistry students must acquire.15 Understanding this concept is key to understanding a wide range of topics in modern chemistry, such as the structure and function of biomolecules, industrial catalysts, and synthetic polymers.17 An example of a common misconception that students have is they tend to forget the influence of lone-pair electrons on the shape of molecule. The presence of lone pairs is an important consideration when predicting the shape of a molecule.17 In order to help students gain a better understanding of these concepts, an activity has been developed that is supported by simple molecular models. Activity cards allow students to work through the steps required to predict the shapes of molecules in an engaging way that facilitates peer learning. Games are used by many instructors and teachers because it is known that they can result in engaging learning experiences.20,21 Orlik22 highlighted that educational games are one of the most valuable instruments to engage students in learning science, particularly chemistry. It is quite important that educational games facilitate student learning, at either the cognitive or affective level, in order to reduce misconceptions and support the development of favorable attitudes toward chemistry.23

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Molecular Models

The molecular models were made using polystyrene balls, cocktail sticks (simple wooden toothpicks), and push pins (Figure 3). The polystyrene balls were provided in a variety of

DESCRIPTION OF THE ACTIVITY

Design of the Cards

The activity card and molecular model are designed to explain VSEPR theory and its implementation to predict the shape of molecule. The activity is designed to be played in pairs. Each pair is given one set of the cards (Figure 2), a copy of the periodic table, a worksheet, and a molecular model. Eleven different packs of the activity card have been developed. Each pack is based on a different example molecule: NF3, BF3, ClF3, CCl4, PCl5, SF4, SF6, BrF5, XeF4, SnCl2, and NO2+. The size of each card used in the game is 14 cm × 10 cm, and the cards are printed on thick paper. There are 36 cards consisting of the cover, the learning objectives, the instructions,

Figure 3. Examples of polystyrene balls, cocktail sticks, and push pins specifically needed for assembling a model of the molecule indicated on the plastic bag. B

DOI: 10.1021/acs.jchemed.7b00687 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

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• To apply VSEPR theory to predict the shape of molecules. • To understand the real shape of a molecule by assembling the molecular model of it.

sizes to allow students to visualize the central atom and its substituents. Cocktail sticks were used to represent bonds between the central atom and the substituents. Push pins were used to depict lone pairs. To differentiate between the central atom and the substituents, the polystyrene balls were painted in different colors. To describe the molecules, teachers often use modeling kits such as the Molymod set. This type of model does not allow lonepair electrons to be shown when describing molecular geometry. Therefore, this model cannot fully describe the effect of lone-pair electrons on the shapes of molecules. Molecular models made from polystyrene balls could show the unshared electron around the central atom by locating the push pins on the central atom. Therefore, students will learn how the unshared electron at the central atom will affect the shape and bond angle of molecules. Moreover, polystyrene balls, cocktail sticks, and push pins are easy to obtain and very easy to make (Figure 4). This is a good

How To Do the Activity

The procedure of the activity has five general steps. First, each group gets a set of cards for a sample molecule whose shape must be predicted. Printable versions of the activity cards for 11 molecules (NF3, BF3, ClF3, CCl4, PCl5, SF4, SF6, BrF5, XeF4, SnCl2, and NO2+) are provided in the Supporting Information. Next, each group works in pairs to answer the questions on the cards. The cards include instructions for the students to follow. The right answer will lead students to the next questions, while wrong answers will lead students back to the previous question card. Cards for wrong answers also provide hints at the bottom of the cards to help students correctly answer the questions. A detail of questions from the cards is provided in Table 1; the example shown is for NF3. After students have answered all the questions, they make models of the molecule based on their answer for card 35, using the specific polystyrene balls, cocktail sticks, and push pins provided in the bag for their molecule. Next, students discuss the steps of predicting the shape of the molecule on the basis of the questions that they answer and write down in the worksheet. A printable version of the activity worksheet is provided in the Supporting Information. It is also helpful for students to consult a periodic table; depending on the learning environment, one may be available on the wall, on an electronic device, or instructors may wish to print a version and add that to each activity card set. A printable version of the periodic table is available through http://www.periodni.com/ download/periodic_table-color.png. The last step is collecting the worksheets and discussing with the whole class whether the shape of molecule students made by assembling the molecular model is correct or incorrect. This step serves as a check that the shape students assembled matches the shape that they see on the activity card. A video is available through https://youtu.be/ 872N7GUSswU that shows two students engaged in the activity using cards to learn about how to predict the shape of molecule based on VSEPR theory; they build a molecular model and write, using their own words, the steps of how they predicted the shape of the molecule, on the worksheet.

Figure 4. Molecular model examples using cocktail sticks to represent bonds between the central atoms and substituents and push pins to represent lone-pair electrons.

option to teach these concepts especially for schools located in remote regions with poor Internet access and with low budgets, as the cards and models are inexpensive, thus making the learning experience accessible. Aims of the Activity

This activity was designed, tested, and revised to achieve the following pedagogical objectives with students: • To understand the effect of lone-pair electrons to the shape of a molecule. • To describe VSEPR theory. Table 1. Contents of the Activity Cards for the Example of NF3 Type of Card Introductory cards Questions cards

Correct answer cards Wrong answer cards

Content of the Cards

Card Number(s)

How to play, learning objectives, introduction, terms, sample molecules What is the central atom in this example? What is the total number of electrons that N has? How many valence electrons does N have? What is the total number of electrons that F has? How many valence electrons does F have? How many electrons are used by each F atom to make bonds with the central atom? What is the coordination number? How many bond pairs (BP) and lone pairs (LP) are there around the central atom? What is the Lewis structure of NF3? Based on your Lewis structure, what is the shape of the molecule? Feedback and hints C

1−6 7 8 11 14 18 20 22 26 28 31, 33 Answer given at the start of the next question and card 35 9, 10, 12, 13, 15, 16, 17, 19, 21, 23, 24, 25, 27, 29, 30, 32, 34, 36 DOI: 10.1021/acs.jchemed.7b00687 J. Chem. Educ. XXXX, XXX, XXX−XXX

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Activity

EVALUATION

The simplicity of the rules, the engaging nature of the activity cards, and the usefulness of the molecular model were also noted by students. Furthermore, 100% of students (N = 20) responded that they either agree and strongly agree that the instructions were easy to follow. 100% of them enjoyed doing the activity, and 100% of students reported that they either agree or strongly agree that the molecular model could help them visualize the shape of molecules. As shown in Figure 5, the vast majority of students also responded that they agree or strongly agree with each of the following statements:

Pilot Study

In order to evaluate the feasibility, time, and playability, the activity cards were piloted to 13 volunteers from the first year of the natural sciences degree at the University of Leicester, UK. They learn VSEPR theory in the first semester; when they did the activity, they had not yet encountered the topic. Feedback and recommendations were collected through a questionnaire. The activity cards were played at the end of a chemistry class. The activity was played by three groups, each group consisting of four or five students. After the activity, all students were given a questionnaire. All students agreed that the activity was fun and they enjoyed it, especially when assembling the molecular model. On the basis of observation during the activity, the activity cards were not completely effective if played in the groups consisting of four or five students, since only two or three of these students were active. Therefore, in the evaluation, the activity card was played in pairs. The only negative feedback received related to the size and the color of the cards. The activity cards were revised on the basis of this feedback to make them larger and brighter. Evaluation of the Activity with the Activity Cards and Molecular Models

Following the pilot study, this activity was used with 20 first-year students from the Department of Chemistry Education at the Tanjungpura University in Indonesia. First-year chemistry education students take general chemistry courses for two semesters. VSEPR theory is one of the general chemistry course 1 topics. The activity cards were used in the classroom when the topic was discussed. Students played the activity and completed an evaluation questionnaire at the end. To assess student understanding of the concepts, students were tested both before (pretest) and after (post-test) the game, using the same set of questions. The questions asked the students to predict the shape of different molecules. All students’ scores increased, and the average increase was 25.7 points (maximum score = 100). Students’ average pretest and post-test scores were 40.18 and 65.87, respectively (N = 20). Pretest and post-test data were analyzed using a paired samples t-test, and the result was significant (p = 0.001). The results indicate that the activity card can effectively support student learning of this concept. Details of the t-test results are reported in Table 2.

Figure 5. Distribution of responses of first-year Indonesian students in chemistry education (N = 20) to the statements numbered 1−8 listed previously in the text.

1. The instructions are clear and understandable. 2. I understand the topic by answering the questions. 3. I know how to predict the shape of molecule based on VSEPR theory. 4. The questions are challenging. 5. I enjoyed doing the activity. 6. The presentation of the activity card is interesting. 7. The molecular model was useful 8. I understand the influence of lone-pair electrons by assembling the molecular model. The molecular models used in the activity not only help students visualize the shape of the molecules, but also improved the students’ understanding of the VSEPR concept at the particulate level. The VSEPR model supports the integration of three levels of representations in the study of chemistry. Moreover, the activity showed a positive effect on student learning in the UK and Indonesia even though their educational systems have some significant differences.

Table 2. Comparative Paired Samples Results Test

Mean

N

SD

t-Value

p-Value

Pre Post

40.1875 65.8750

20 20

7.02761 12.38168

0.669

0.001

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Students were very pleased with the activity, as 100% of them responded that they either strongly agree or agree with the statement that they enjoyed doing the activity. In terms of the activity, the results showed a similar trend to the natural sciences students of University of Leicester, in that they were engaged with the activity, especially when they assembled the molecular model. The findings of this study are consistent with previous work on card-based learning activities that have shown this approach can be a good way to engage students and support their learning.24−26 On the basis of a review of the literature, the authors believe that this is the first time this approach to teaching the VSEPR theory, using a combination of cards and molecular models, has been described.

CONCLUSION An activity using simple molecular models, activity cards, and a worksheet was designed as a complementary learning resource to help students develop an understanding of how to apply VSEPR theory. The activity helps students understand the basic concepts of how to predict the shape of molecules based on VSEPR theory in an engaging way, to which 75% and 25% of students either strongly agree or agree, respectively, in response to statement 5. Moreover, using the activity cards and assembling the molecular model helped students understand the effect of lone-pair electrons on the shape of molecules, as demonstrated by 95% D

DOI: 10.1021/acs.jchemed.7b00687 J. Chem. Educ. XXXX, XXX, XXX−XXX

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of students agreeing or strongly agreeing with the final statement (number 8) in the questionnaire that they “understand the influence of lone-pair electrons by assembling molecular model”.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.7b00687. Activity card sets for NF3, ClF3, BF3 (PDF) Activity card sets for CCl4, PCl5, SF6, XeF4 (PDF) Activity card sets for SF4, BrF5, SnCl2, NO2+, (PDF) Activity worksheet (PDF, DOCX)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] or [email protected]. ORCID

Erlina: 0000-0003-4620-1281 Dylan P. Williams: 0000-0002-1260-5926 Notes

The authors declare no competing financial interest. A comprehensive printable periodic table of the elements from IUPAC is available online: http://www.periodni.com/ download/periodic_table-color.png (accessed Feb 2018). A video of how to do the activity is available online: https:// youtu.be/872N7GUSswU (accessed Feb 2018).

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ACKNOWLEDGMENTS This work has been supported by The Ministry of Research, Technology, and Higher Education (KEMENRISTEKDIKTI) Indonesia, and Tanjungpura University. We also thank the Faculty of Teacher Training and Education, our colleagues, and students who were involved in this study.

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REFERENCES

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DOI: 10.1021/acs.jchemed.7b00687 J. Chem. Educ. XXXX, XXX, XXX−XXX