When you hear the word “model” you might immediately think of the small-scale 3-dimensional replicas of buildings used by architects or the typical animal cell model your teacher had you make when you were a student. In science, the term “model” refers to a simplified representation of a system that is used to make predictions or explanations for a phenomenon. Scientific models are “judged on both how simple they are and how well they can be used to explain and predict natural phenomena” (Jadrich & Bruxvoort, 2011, p. 12). Using this definition, the 3D cell model or a drawing of the rock cycle found in so many textbooks are NOT scientific models in and of themselves. They are simply representations (unless they are used to explain or predict). Memorizing the steps in a cycle or the parts of a cell are not the end goal in an NGSS classroom.
According to the Next Generation Science Standards (NGSS), scientific models may include: diagrams, physical replicas, mathematical representations, analogies, and computer simulations (see NGSS Appendix F). But, again, keep in mind that they must be used to predict or explain phenomena.
In this blog, we focus on one specific type of modeling that is particularly helpful for supporting and deepening student learning: “explanatory models.”
Explanatory models are a combination of pictorial representations and written explanations that describe how and why a particular phenomenon occurs. Here are a couple of examples of what these types of models look like:
How does Ebola infect and kill a person?
(Darrin Collins, 2014, Phillips Academy High School)
Why do huge swarms of rats overrun a bamboo forest in India once every 48 years?
(Sarah Rogers, 2015, Howe School of Excellence)
Explanatory models accommodate different learning styles. They don’t just stop at reading and writing, they allow students to visually represent their thinking (i.e., through drawing). Research shows that having students draw out their explanations supports learning (Ainsworth & Iacovides, 2005). Asking students to represent their ideas through illustrations provides a window into their thinking for the teacher and supports students in making sense of the content. Drawing is not only a helpful strategy for ELL and diverse learners who struggle with writing, but for all students.
3 Key Aspects of Scientific Models (Schwarz et al., 2009)
- Include specific variables or factors within a system under study.
- Represent the relationships among components (i.e., variables/factors) in order to provide an account of why the phenomenon occurs.
- Sequence these variables, factors, and relationships into a causal storyline to explain a phenomenon.
As students acquire new learning and evidence over the course of a unit, they need periodic opportunities to revisit and revise their explanatory models. Explanatory models require students to use science principles and ideas to explain real world events/occurrences. Stated another way, explanatory models require students to relate the observable (effects) to their unobservable (causes). According to the research synthesized in the publication, How People Learn, “To develop competence in an area of inquiry, students must...understand facts and ideas in the context of a conceptual framework, and...organize knowledge in ways that facilitate retrieval and application” (NRC, 2000, p. 12). It follows that developing models to explain how and why phenomena occur strongly aligns with research on effective teaching and learning.
NGSS outlines 8 Science and Engineering Practices in which students should regularly engage in order to learn the science content. “Developing and Using Models” is the second of these eight practices.
Check out this AUSL video to see how 3 AUSL teachers have implemented explanatory models in their classrooms.
What are we aiming for when we have students develop and use explanatory model?
- Students create initial models at the beginning of the unit (to elicit their initial ideas/predictions), revise them in the middle (once or twice) based on new learning, and then create a final model at the end (tying together their learning throughout the unit).
- Students defend their additions/revisions to their explanatory models using evidence from sense-making activities (i.e., any classroom activity that supports students in deepening their content knowledge: investigation, simulation, reading, etc.).
- Students are able to connect the unobservable (causes) to the observable (effects) in their explanatory models.
- Students are able to use their explanatory model to make predictions about or explain how and why a phenomenon occurs.
- Students are able to apply their learning to explain how and why a new, related phenomenon occurs (to show that their learning is transferable).
I’m interested in having my students develop and use explanatory models: Where should I start?
The easiest way to get started with modeling is to begin by asking students to do more drawing (i.e., represent the concepts they are learning pictorially). For example, ask students to draw what they think is going on when a liquid evaporates, or better yet, draw how they think a puddle disappears after it rains. While explanatory models for big questions, such as “How can we smell the cookies baking at the factory 10 blocks away,” requires students to connect and synthesize several science ideas in one explanation, the modeling activity to the right was used to have students explain a single concept: air compression in a syringe. If you are new to modeling, we recommend starting by having students draw pictures of their ideas around a single concept. As you and your students become more comfortable, you can start asking them to draw models to explain or predict more complex, multi-concept, questions.
Why is it difficult to push in the plunger of a syringe filled with air when your finger is covering the opening?
(Alexa Young, 2015, Marquette School of Excellence)
Things to keep in mind as you get started with modeling…
- Don’t give the answers away! Let students struggle.
- Respond to students’ questions with questions (e.g., What did you observe? What do you think it means? Why do you think that? Where have you seen something similar?)
- Give them time. Allow them to share ideas with each other and edit their models.
- Discuss and agree on common drawing conventions (e.g., how to draw different types of particles, how to show motion, how to represent different speeds, etc.)
- Use “zoom-in’s” (like the picture of the syringe above) and ask students to use “microscope eyes” to illustrate and explain things that are invisible to the naked eye (e.g., layers of the earth, gases, etc.)
- Have students label with arrows and/or make a key/legend.
- Have students describe what’s going on in their pictorial models through writing (in full sentences).
How do explanatory models align with Model-Based Inquiry (MBI)?
Based on its name alone, it’s clear that MBI is inextricably linked to modeling. Developing, testing, revising, and evaluating explanatory models is the skeleton around which MBI units are designed. For each unit, you change the phenomenon and you change the content/science ideas addressed, but you go through the same modeling process: 1. develop initial models; 2. revisit, test, and revise models to improve their predictive and explanatory power; 3. create final models; and 4. apply learned science ideas by creating an explanatory model for a new related phenomenon.
How do explanatory models align with NGSS?
Not only are explanatory models at the heart of MBI, but they are at the heart of science in general! “The primary goal of science is the construction and evaluation of scientific models” (Jadrich & Bruxvoort, 2011, p. 12). All of the 8 science and engineering practices outlined in NGSS are tightly tied to modeling. Put modeling at the center of your classroom and you’ll find innumerable opportunities to weave in the other practices integral to the scientific endeavor. Since modeling is salient to MBI, this further reinforces why MBI is such an effective approach to planning and teaching science in line with the vision of NGSS.
Many thanks to Alexa Young, from Marquette School of Excellence, for co-writing this blog, as well as the teachers across our network who are engaging their students in MBI and sharing photos of their students’ work from which we all get to benefit!
Ainsworth, S., & Iacovides, I. (2005). Learning by constructing self-explanation diagrams. In 11th Biennial Conference of European Association for Research on Learning and Instruction, Nicosia, Cypress.
Jadrich, J., & Bruxvoort, C. (2011). Learning & Teaching Scientific Inquiry: Research and Applications. NSTA press.
National Research Council. (2013). Next Generation Science Standards: For states, by states. Washington, DC: National Academies Press.
Schwarz, C. V., Reiser, B. J., Davis, E. A., Kenyon, L., Achér, A., Fortus, D., Shwartz, Y., Hug, B., & Krajcik, J. (2009). Developing a learning progression for scientific modeling: Making scientific modeling accessible and meaningful for learners. Journal of Research in Science Teaching, 46(6), 632-654.