Activity pubs.acs.org/jchemeduc
Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom Ted M. Clark†,* and Julia M. Chamberlain‡ †
Departments of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States Department of Physics, University of Colorado Boulder, Boulder, Colorado 80309, United States
‡
S Supporting Information *
ABSTRACT: An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six atomic models presented in the simulation, which provides explicit visual representations of abstract concepts. When used together, the activity and simulation address the important and challenging topic of science as model development, and offer students insight into the nature of science. Survey results indicate a positive response from students for laboratory activities, like this one, that include computer simulations.
KEYWORDS: First-Year Undergraduate/General, Computer-Based Learning, Inquiry-Based/Discovery Learning, Atomic Properties/Structure, Atomic Spectroscopy, Student-Centered Learning
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INTRODUCTION Atomic theory is a principal concept in general chemistry. It has been described as a threshold concept, suggesting that misconceptions in this area may affect understanding of subsequent topics such as spectroscopy and bonding theory.1 Indeed, an inability to apply atomic modeling skills in an expert manner may limit one’s ability to explain other phenomena, such as ionization energy,2 or to understand quantum concepts.3 A strong understanding of atomic modeling and an ability to use models as tools for scientific reasoning are important attributes for success in general chemistry and beyond.4 In first-year undergraduate chemistry courses, it is common to initially introduce, compare, and contrast a modern description of atomic structure, including protons, neutrons, electrons, a nucleus, isotopes, and so on, with earlier models proposed by Democritus and Dalton, and then return to this topic when discussing quantum theory and the electronic structure of atoms. Because of the abstract nature of an atom, and the fact that various models have been used to explain and support scientific observations, aspects of this narrative have also been used to illustrate the tentative, developmental nature of scientific knowledge.5,6 E-learning resources, including PhET7 interactive simulations, have improved students’ conceptual understanding, insight into the nature of science (NOS), and awareness of historical experiments when incorporated into technologyenhanced chemistry classrooms.8,9 To reach a greater number of students, activities and practices from technology-enhanced © XXXX American Chemical Society and Division of Chemical Education, Inc.
classrooms must transfer to general instruction, such as traditional large-enrollment lecture rooms, recitation classrooms, and outside of class.10,11 The use of simulations in laboratories, and pairing them with hands-on experiments, is another strategy with great potential.12−14 This article describes an activity suitable for use in introductory courses, along with its recent use in general chemistry labs enrolling a large number (∼2500/semester) of students, and examines student attitudes toward inclusion of a simulation-based activity in an instructional laboratory.
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DESCRIPTION OF SIMULATION AND ACTIVITY The Models of the Hydrogen Atom simulation15 was developed in response to the observations that, even following extensive instruction in an upper-level physics course, many students had difficulty understanding the reasoning that led to different atomic models, and did not have clear mental pictures of these models.16 The simulation presents an animated, interactive interface allowing exploration of six different atomic models: Dalton’s Billiard Ball, Thomson’s Plum Pudding model, Rutherford’s Classical Solar System model, the Bohr and de Broglie models, and finally Schrödinger’s quantum mechanical model (Figure 1). In the simulation, photons are directed at a hydrogen atom, and students observe the resulting interactions, emission spectrum, and electronic transitions consistent with each model. Students can manipulate the energy of the photons by selecting polychromatic or monochromatic radiation of a
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Figure 1. Models of the Hydrogen Atom simulation showing the Bohr model following a ni = 3 to nf = 2 electronic transition. The center animation shows a cartoon representation of photons interacting with a Bohr model hydrogen atom, while the corresponding energy-level diagram shows animated transitions between levels. The accompanying line spectrum grows as photons are recorded for each transition. A note that “drawings are not to scale” cues students that the representations presented are cartoons and that, for the purpose of observing and interacting with each model, the parts of the atom are not drawn with accurate proportions.
the symbolic (energy-level diagram) and macroscopic observable (the spectrometer). The format of questions within the activity varies, including multiple-choice, closed- and open-ended questions, concept tables, and prompts for sketches. For increased relevancy and better integration with the lecture content, some activity questions are based on common student difficulties (e.g., converting between units and calculating the energy of 1 mol of photons given their wavelength).
particular wavelength, and speed can be adjusted for easier observation of individual electronic transitions (slow) or more efficient collection of emission spectra (fast). An important design feature of the simulation is that it offers multiple representations for each model,17−19 so that students can coordinate between the atom animation, the electron energylevel diagram, and the predicted atomic emission spectrum. In addition to comparing the six atomic models, students can examine the hydrogen atom in an experimental mode with photons being directed into a “black-box” (the atom’s structure is hidden and the emission spectrum from the quantum mechanical model is generated). Like other black-box activities, this allows students to make indirect observations of a macroscopic observable (the emission spectrum) and infer or examine underlying characteristics of the object.20,21 In this activity, students collect an experimental emission spectrum from the black box, and proceed in a guided investigation of each model’s prediction. Students describe each model, see how photons interact with the atom, and observe the resulting emission spectrum with a goal of identifying the model that best agrees with the experimental data. The pedagogical approach is inductive, beginning with guided inquiry in which the questions or problems provide a context for learning,22 and shifting to a more open-ended “student sense-making mode”23 for the Bohr model. In the Bohr model investigation, students are challenged to make connections between the particulate representation (the atom and photons)
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ACTIVITY IMPLEMENTATION The activity was used in general chemistry laboratories in the seventh week of the semester-long course. The lecture topics for this week focused on the electronic structure of atoms. Seven different instructors were responsible for the lecture portion of the course and their approaches and treatment of the content varied. For example, some instructors prioritized a conceptual understanding of different models, others explicitly discussed NOS material, and so forth. A prelab video24 (accessed by ∼25% of students) and the printed activity were made available to students prior to lab and a prelab quiz was administered online in the days preceding lab. Students were encouraged to download the simulation before attending lab. Approximately 90% of the students brought their own computers to lab and about one-half arrived with the simulation loaded. Downloading the simulation within the lab period was not difficult. In general, all students in a lab section B
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of 25 began working on the activity within the first 10 min of lab. Students were encouraged to work in groups of two to three, and most frequently every student in the group had access to a computer. In a typical lab section, a few students chose to work independently and they were not forced to form a group with classmates. Extra computers were available, but they were rarely used as students preferred to work with classmates if they had technical problems loading or running the simulation. Because the resources were available in advance, a small number of students started their investigations before arriving in lab. The activity itself took approximately 60−90 min to complete, although the time spent in lab varied considerably. Some student remained in lab, working with classmates for the entire duration (3 h). The activity was paired with a common general chemistry experiment in which students use gas discharge lamps to observe and record the line spectra for hydrogen and helium (see the Supporting Information). A teaching assistant managed the session by having small groups of students access the discharge lamps throughout the lab period in the adjacent darkened balance room. Use of the simulation was therefore interrupted at different points for different student groups. The laboratory grade was composed of the prelab quiz (10%), in-class participation (30%), and a postlab online quiz (60%).
Information). Overall student satisfaction was quite high, with 86% of respondents liking or strongly liking the activity. Student perceptions of the material environment (the resources in, or brought to, lab) were extremely high, as students were quite willing to bring a computer to lab and did not have difficulty accessing the simulation software. When working on the simulation in lab, students clearly favored working with a partner and discussing their work, leading to a favorable view of student cohesiveness. It is not uncommon for students to perceive a tension in lab between rule-clarity (knowing what must be done, how to do it) and open-endedness (opportunity for decision-making). Students in this investigation viewed the degree of instruction as being reasonable (8% favored fewer instructions, 38% favored more instructions, the majority favored the current format). The integration of lab with the course was quite high, with 89% of respondents identifying the activity as being more integrated with lecture than a typical lab. In addition, two-thirds held that this activity led to greater learning than a typical lab; only 16% thought it led to less learning. An aim of this activity was to raise awareness of the role of models for both students and instructors. Here, models may be viewed as tentative schemes or structures with explanatory power that correspond to real objects or events31 with a distinction being made within the activity between physical models (that replicate very small or very large objects on a more convenient scale) and conceptual ones (that describe systems that cannot simply be rescaled to become visible, such as the weather, the economy, or atoms).32 The classification of models, of course, goes far beyond this simple distinction.33 However, because students are often primitive modelers, for example, viewing models as exact representations or finding multiple and competing models difficult to understand, this distinction was highlighted.34,35 It is difficult to overstate the importance of models to chemists. Indeed, Gilbert holds that science may be defined as “a process of constructing predictive conceptual models”.36 Topics throughout science curricula employ models and scientific models are often the only way to explain abstract scientific theories, including the models of the atom illustrated within this activity.37 Activities in which students are instructed about the nature and purpose of models in science have been positively related to modeling gains for chemistry students4 and it is held that interactive activities employing models, like the one described here, contribute to this conversation. In several respects this activity is consistent with pedagogical recommendations about teaching with analogical models.35 It is important that teachers regularly check the students’ visualization of the model, especially if the model was designed by scientists and is unfamiliar to students. That is certainly the case with atomic models, and so having a common point of reference (the simulation) is valuable. Also valuable is the presentation of different atomic models, as this may support a discussion of the legitimacy, desirability, and overlap of scientific models. This activity, however, is not intended to be a comprehensive treatment of modeling in general chemistry. The arbitrary nature of models, their use as tools for predicting and explaining, their tentative and developmental nature as understanding improves, all require explicit instruction that goes well beyond a single laboratory experiment.35,38,39 This activity involves learners observing models, but it does not task them with constructing, testing, and revising their own
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DISCUSSION The notion that introductory chemistry labs are suitable for the inclusion of interactive simulations was tested here on a large scale. Logistically, the implementation of simulations was a clear success as accessing and using technology was not a problem. As technology becomes ubiquitous in higher education, attention is shifting to questions of technology usage, not of providing access to technology.25 This activity’s implementation is similar to other investigations that have included computer simulations within the laboratory itself14 albeit on a much larger scale. The emission spectrum of hydrogen is a noteworthy experiment suitable for such a pairing in that it has historical significance, may support NOS learning objectives and model development,6,26 and is experimentally accessible in an introductory laboratory course.27 Emission spectra provide important insights into the nonclassical realm of quantum mechanics,28 yet connecting these experimental data with an underlying atomic model, or models, is not a trivial task. The “troublesome” nature of atomic models and their abstractness makes visualization at the particle-level challenging.1 A relevant feature of the Models of the Hydrogen Atom simulation is its particle-level depiction of six atomic models ranging from the classical to the quantum mechanical. Students repeatedly commented on how they could now “see what the theory was like”. This is consistent with the goal of using the simulation to support the students’ mental construction of atomic models.16 As noted, seven different instructors presented information on the topic of electronic structure of atoms in lecture, making evaluation of simulation-specific learning gains difficult to quantify. Instead, we consider here student perceptions of their simulation use in lab. A survey was constructed based on dimensions of laboratory instruction shown to be linked to student satisfaction in instructional labs,29,30 that is, material environment, student cohesiveness, rule clarity, open-endedness, and integration with class (see the Supporting C
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models.38 However, the fact that simulations can be employed on a large scale in a manner that students enjoy and feel contributes to their learning suggest that further use of simulations and their effectiveness is worthwhile, and that such simulations may prove useful for students’ development as modelers.
(12) Liu, X. Effects of combined hands-on laboratory and computer modeling on student learning of gas laws: A quasi-experimental study. J. Sci. Educ. Technol. 2006, 15 (1), 89−100. (13) Zacharia, Z. C. Comparing and combining real and virtual experimentation: An effort to enhance students’ conceptual understanding of electric circuits. J. Comput. Assisted Learn. 2007, 23, 120− 32. (14) Jaakola, T.; Nurmi, S. Fostering elementary school students’ understanding of simple electricity by combining simulation and laboratory activities. J. Comput. Assisted Learn. 2008, 23, 271−283. (15) Models of the Hydrogen Atom. http://phet.colorado.edu/en/ simulation/hydrogen-atom. (accessed Mar 2014). (16) McKagan, S. B.; Perkins, K. K.; Wieman, C. E. Why we should teach the Bohr model and how to teach it effectively. Phys. Rev. ST Phys. Educ. Res. 2008, 4, 1−10. (17) Adams, W. K.; Reid, S.; LeMaster, R.; McKagan, S. B.; Perkins, K. K.; Dubson, M.; Wieman, C. E. A Study of Educational Simulations Part I − Engagement and Learning. J. Interactive Learn. Res. 2008, 19 (3), 397−419. (18) Adams, W. K.; Reid, S.; LeMaster, R.; McKagan, S. B.; Perkins, K. K.; Dubson, M.; Wieman, C. E. A Study of Educational Simulations Part II − Interface Design. J. Interactive Learn. Res. 2008, 19 (4), 551− 577. (19) Lancaster, K.; Moore, E. B.; Parson, R.; Perkins, K. K. In Pedagogic Roles of Animations and Simulations in Chemistry Courses; Suites, J. P., Sanger, M. J., Eds.; American Chemical Society: Washington, DC, 2013; http://pubs.acs.org/isbn/9780841228269 (accessed Mar 2014). (20) Yayon, M.; Scherz, Z. The return of the black box. J. Chem. Educ. 2008, 85 (4), 541−543. (21) Records, R. M. Developing models: What is the atom really like? J. Chem. Educ. 1982, 59 (4), 307−309. (22) Prince, M. J.; Felder, R. M. Inductive teaching and learning methods: Definitions, comparisons, and research bases. J. Eng. Educ. 2006, 95 (2), 123−138. (23) Adams, W. K. Student engagement and learning with PhET interactive simulations. Il Nuovo Cimento 2010, 1−12. (24) Clark, T. OSU Laboratory Experiment: Emission Spectra & Atomic Models. http://www.youtube.com/watch?v=dGWYEkiUFgw (accessed Mar 2014). (25) Smith, S. D.; Caruso, J. B.; Kim, J. The ECAR Study of Undergraduate Students and Information Technology, Research Study; EDUCAUSE Center for Applied Research: Boulder, CO, 2010; Vol. 6; available from http://www.educause.edu/ecar (accessed Mar 2014). (26) Leary, J. J.; Kippeny, T. C. A framework for presenting the modern atom. J. Chem. Educ. 1999, 76 (9), 1217−1218. (27) Bopegedera, A. M. R. P. A guided-inquiry lab for the analysis of the Balmer series of the hydrogen atomic spectrum. J. Chem. Educ. 2011, 88 (1), 77−81. (28) Shields, G. C.; Kash, M. M. Experiment in quantization. J. Chem. Educ. 1992, 69 (4), 329−331. (29) Fraser, B. J.; Giddings, G. J.; McRobbie, C. J. Evolution and validation of a personal form of an instrument for assessing science laboratory classroom environments. J. Res. Sci. Teach. 1995, 77, 1−24. (30) Henderson, D.; Fisher, D.; Fraser, B. Interpersonal behavior, laboratory leaning environments, and student outcomes in senior biology classes. J. Res. Sci. Teach. 2000, 37, 26−43. (31) National Research Council. National Science Education Standards; National Academy Press: Washington, DC, 1996. (32) Suchocki, J. A. Conceptual Chemistry; Pearson Benjamin Cummings: San Francisco, CA, 2007. (33) Harrison, A. G.; Treagust, D. F. A typology of school science models. Int. J. Sci. Educ. 2000, 22 (9), 1011−1026. (34) Grosslight, L.; Unger, C.; Jay, E. Understanding models and their use in science: Conceptions of middle and high school students and experts. J. Res. Sci. Teach. 1991, 28 (9), 799−822. (35) Harrison, A. G.; Treagust, D. F. Learning about atoms, molecules, and chemical bonds: A case study of multiple-model use in grade 11 chemistry. Sci. Educ. 2000, 84 (3), 352−381.
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CONCLUSION The Models of the Hydrogen Atom PhET simulation and accompanying activity are valuable additions to introductory courses as they support the mental construction of atomic models by students, demonstrate the tentative nature of scientific knowledge, and engage students in inquiry-based sense-making activities. The successful implementation of these resources in laboratory classes on a large scale was demonstrated in terms of student views and logistical feasibility, suggesting their transfer to other traditional instructional settings is both possible and warranted.
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ASSOCIATED CONTENT
* Supporting Information S
Laboratory activity; discharge lamp activity; student survey responses. This material is available via the Internet at http:// pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
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(36) Gilbert, S. Model Building and a Definition of Science. J. Res. Sci. Teach. 1991, 28 (1), 73. (37) Treagust, D. F.; Chittleborough, G.; Mamiala, T. L. Students’ understanding of the role of scientific models in learning science. Int. J. Sci. Educ. 2002, 24 (4), 357−368. (38) Schwarz, C. V.; Reiser, B. J.; Davis, E. A.; Kenyon, L.; Achér, A.; Fortus, D.; Shwartz, Y.; Hug, B.; Krajcik, J. Developing a learning progression for scientific modeling: Making scientific modeling accessible and meaningful for learners. J. Res. Sci. Teach. 2009, 46 (6), 632−654. (39) Criswell, B. Do You See What I See? Lessons about the Use of Models in High School Chemistry Classes. J. Chem. Educ. 2011, 88 (4), 415−419.
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