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Chemistry Solutions
November 2019 | Nuts & Bolts
Developing the Skill of Modeling to Reinforce Complex Topics in Chemistry
By Alden A. Zimlich
Modeling, Instructional Strategies
With the release of the Next Generation Science Standards (NGSS), many teachers are searching for answers to questions related to the practice of modeling in the science classroom. Although models have been used in many varieties in science, the practice of modeling has been at the forefront most recently, and it has shown its ability to help students gain a better conceptual understanding of concepts, as well as develop their reasoning skills.^{1,}^{2} The work described in these articles is based upon Modeling-Based Learning, in which the teacher develops and organizes an environment that allows students to self-regulate their learning through their interactions with the presented information.^{3} Instruction about the practice of modeling follows a progression throughout a school year that starts with simple concepts and ends with the synthesis of several concepts that model complex solution chemistry.
The first step: modeling something familiar
Figure 1. An example of an Idea Bank to capture student ideas on what good models should include (photo courtesy of Karen O’Connor). |
The foundational work begins with asking students to create a model of something familiar. An engaging, beginning-of-the-year activity could be to ask the students to create a model of themselves. This would familiarize the students with one another, as well as trigger a conversation regarding elements of a good model. This activity can also assist in establishing the classroom culture of positive feedback and having a growth mindset.
Once the students have drawn their models, ask them to trade their model with another student (or pass the model around the table if they are situated in groups). You can then ask them to provide feedback on a peer’s model with the guidance of a prompt such as, “Provide one or two good qualities of that model,” or “Provide two reasons that this model represents the person who drew it.” The students can then pass the model back (or around their group until it is returned to the originator) and get some positive feedback from their peers.
Once the students have received feedback about their models from their peers, the class can create an “idea bank” (shown in Figure 1), where they can document the qualities that they feel are elements of a good model. After completion of the idea bank, you can extend their understanding of modeling with a reflection prompt. Present the following types of questions as an exit ticket or a prompt for a transition: “Does your model allow you to describe yourself beyond how you look?” or “Can your model be used to describe how good you are at ______ (sports, music, science, math, etc.)?”
As an additional possibility, you can present the students with your baby picture, your high school yearbook picture, and your faculty picture as a model of yourself. This would introduce the concept of time passing as an important aspect of models, as well as the idea of a key being a useful part of a model. Again, using prompting, ask them questions about why this series of pictures is a better model than one of these pictures alone.
The next step: modeling to strengthen skills
A brainstorming session based upon the “familiar model” is an appropriate next step. The students can generate essential elements of a “good model” based upon what they learned from their first model and their reflections on the initial activities. Which characteristics define a good model can vary from teacher to teacher. I encourage creativity and authenticity, so for my students a key is a necessary element, since the individual models have considerable variation. Additionally, it has been learned that the illustration of time (before-during-after) is an effective way to assist students in communicating their thought process during modeling.^{4}
Once the class has established the qualities of a good model with the guidance of the teacher in a brainstorming session, you can use a small group model to further their understanding of modeling. A collaborative approach to modeling promotes several scientific practices, such as argumentation, data analysis, and interpreting evidence.^{5} The phenomena used for this model can vary greatly depending upon what is available to the classroom. Examples that would be appropriate for a group model at this stage could be a lava lamp or the dissolving of a sugar cube in water; in any case, it helps for the students to focus on a particular aspect of the phenomenon in their model. For example, the focus on the lava lamp could be the rising and falling of the substance and how this phenomenon gets captured in a model. The focus of the sugar dissolving could be the solid changing to an aqueous form, thus showing a change from a solid to moving aqueous particles in the water.
Feedback on the student models can be handled similarly as the first model; however, at this stage, I like to present a good model to the class that was created by a group of students. Monitoring by walking around can assist you in developing their skill and finding an appropriate model to share. As the class creates their model, individual students can be prompted with guiding questions to assist them in creating a better model than they could without guidance; however, the prompts should be open-ended to provide the students the opportunity to develop their reasoning skills. For example, if a group of students didn’t show a before-during-after model, you could ask, “How are you showing movement over time in your model?” After sharing a good example (or two) with the class, the students should have the opportunity to modify their model and perform some reflection regarding what they did well and what they can do better in future models. A prompt that I like to present to the students after this group model is, “How can your model be modified to represent the macro and microscopic nature of matter?”
Beginning modeling with unit context
Now that the students have been introduced to modeling, established their criteria for a good model, and learned how to capture motion and time in a model, you can present a new phenomenon relevant to the first unit. In my class, our first phenomenon is a video of a supernova. This is the first of many phenomena used to develop their modeling skills and the related unit is focused on the elements, atomic structure, and the periodic table. After presenting the supernova video to the students, the students are asked to brainstorm about the phenomenon. We develop a “driving question board” to help the students share their questions about what information might help them better understand what is occurring and to assist the teacher in preparing lessons to address these questions throughout the unit. Once the class has created the driving question board, I ask them to create a model of the supernova based upon what they observed.
Since there is no instruction or prompting about elements, supernovae or fusion, the students will struggle with the first model. A picture of a typical initial model can be seen in Figure 2. This is simply a starting point for the students. Again, teacher prompts are useful for the students to expand their models into more than a sketch. After the students have completed their initial model, they can trade models with a partner and provide positive feedback. Once the collaboration has completed, the students share any positive feedback they felt was compelling with the entire class. During the sharing, I recommend focusing on the elements that have been deemed relevant for a good model. A few examples of items that I look to emphasize are:
- a key being present,
- an appropriate scale being used,
- a before-during-after representation,
- scientific accuracy, and
- the model being clear/concise.
Throughout the unit, as specific concepts are taught, the students should modify their models to incorporate the specific concept in the model. For example, the initial model most likely will not include any representation of fusion but, after the concept has been taught, you can use a prompt for model modification: “Now that we understand that this is a supernova and fusion is occurring, add this process to your model.” Adding sticky notes to the model as the student ideas shift is an effective means to capture their growth, but modification of the models should be kept to two or three to prevent model fatigue^{4}. Ultimately, I have my students consolidate their ideas on their initial model and then create one final model. An example of a final student model can be seen in Figure 3, and an ideal model in Figure 4.
Feedback and reflection
An important way to support students’ growth in the skill of modeling is to provide them feedback on what was initially created. Whether this feedback is provided by the teacher as traditional formative feedback, a teacher’s questioning prompt, the peers’ positive feedback, or a self-reflection based or some combination of these would be at the teacher’s discretion. Additionally, once the feedback is provided, the students should have the opportunity to act on that feedback. This process should ultimately end in some modification of the student model to address their reflection and support their growth in reasoning skills. For the introductory model, the focus should be to reinforce the key components of a model; for my class, this model is about a key being present, the scale is appropriate for each snapshot in time, a before-during-after representation, and the scientific details present are relevant to the phenomenon at hand.
Adding complexity
As the school year progresses, the students continue to apply their modeling skills to various phenomena and receive appropriate feedback to foster positive growth. This is challenging work, because the teacher must be able to recognize the weaknesses of the students’ modeling ability and provide ways to support growth in that area. This type of instruction relates to a differentiated classroom, where different skill levels should be provided with different levels of support and/or activities for growth.^{6} Through formative feedback, appropriate prompting, and reflection, the modeling skill can improve. An example of modeling with more complexity is modeling chemical reactions, and Figure 5 shows an example of a single displacement reaction being modelled.
At this point in the year, the student has learned about atomic and ionic size, and also that breaking bonds is an endothermic process, while bond creation is exothermic — so the expectation is that these concepts will be present in the model. Additionally, the collision theory was introduced, so orientation of the collision is also displayed in the model. The obvious omission to this model is solubility; however, that can be a component of the model if desired (as is the case in the last example).
Modeling the complex
The last unit of study is acid/base chemistry. Although this does not fall specifically in the NGSS curriculum, it does capture many of the concepts that are taught throughout the year and synthesizes them into a challenging conclusion at the end of the course. Weak and strong acids are discussed, as well as the method of titration. In this example the students create a model of a titration occurring over time. The expectation of this model is for the students to incorporate all relevant topics that were learned, as well as keeping the model as concise as possible. An example of this model is shown in Figure 6.
This model allows students to demonstrate their understanding of the concept of equilibria of a weak acid, a double displacement reaction with solubility rules applied, and the process of a titration including the key points of the titration (the ½ equivalence point and the equivalence point). The student could indicate motion of the particles but this is solution chemistry and the student should make an editorial decision to include the most relevant scientific principles to model.
Conclusion
The use of particulate diagrams to visualize complex phenomena in chemistry is a modeling skill that most teachers use — but it is also a skill that can be taught. The focus is on the practice of modeling, not the model itself. Using an inquiry-based approach, you can present students with phenomena and then ask them to create a model that explains them, providing students the opportunity to build their modeling skills. Starting with simple concepts, providing feedback, appropriate question prompts, and an opportunity for reflection allows students to become successful in the skill of modeling. Building upon the simple concepts with different phenomenon and covering various content areas helps the students broaden their knowledge and ability to model more complex behavior.
Acknowledgements
Thanks to Karen O’Connor and Caroline Humes for their valuable input during the editing process.
References
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- Harrison, A.; Treagust, D. Secondary students’ mental models of atoms and molecules: implications for teaching chemistry. Science Education. 1996, 80, no. 5, 509-534.
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- Windschitl, M.; Thompson, J. The Modeling Toolkit: Making Student Thinking Visible with Public Representations. The Science Teacher. 2013, 80, no. 6, 63-69.
- Hogan, K. Relating students’ personal frameworks for science learning to their cognition in collaborative contexts. Science Education. 1999, 83, no. 1, 1-32.
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