Science & Engineering Practices:
2. Developing and Using Models
Modeling can begin in the earliest grades, with students’ models progressing from concrete “pictures” and/or physical scale models (e.g., a toy car) to more abstract representations of relevant relationships in later grades, such as a diagram representing forces on a particular object in a system.(NRC Framework, 2012, p. 58) Models include diagrams, physical replicas, mathematical representations, analogies, and computer simulations. Although models do not correspond exactly to the real world, they bring certain features into focus while obscuring others. All models contain approximations and assumptions that limit the range of validity and predictive power, so it is important for students to recognize their limitations.In science,models are used to represent a system (or parts of a system) under study, to aid in the development of questions and explanations, to generate data that can be used to make predictions, and to communicate ideas to others. Students can be expected to evaluate and refine models through an iterative cycle of comparing their predictions with the real world and then adjusting them to gain insights into the phenomenon being modeled.As such, models are based upon evidence. When new evidence is uncovered that the models can’t explain, models are modified. In engineering,models may be used to analyze a system to see where or under what conditions flaws might develop,or to test possible solutions to a problem. Models can also be used to visualize and refine a design, to communicate a design’s features to others, and as prototypes for testing design performance.
Modeling in grades 3–5 builds on previous experiences and progresses to building and revising simple models and using models to represent events and design solutions. - Identify limitations of models. - Collaboratively develop and/or revise a model based on evidence that shows the relationships among variables for frequent and regular occurring events. - Develop a model using an analogy, example, or abstract representation to describe a scientific principle or design solution. - Develop and/or use models to describe and/or predict phenomena. - Develop a diagram or simple physical prototype to convey a proposed object, tool,or process. - Use a model to test cause and effect relationships or interactions concerning the functioning of a natural or designed system Here, we refer to models as representations of systems, so we can better understand the parts of a system and how they work together. This can help us explain phenomena and make predictions. Over time, students need to refine their models to show their thinking and understanding. They must revise and adapt their model when they encounter a situation that cannot be explained by applying their existing model. |
Suggestions for High-Quality Models:
A = Accurate B = Big; take up most of the page C = Colorful D = Detailed; include key details Also: - Show concepts (not just pictures) - Show functions (of the parts of a system) - Decode, understand, test, and refine others' models; see where you can extend or adapt simulations. - Identify the abstractions, limitations, and assumptions made in models - Use dynamic models that “act like” the system modeled and show change over time There are several types of models: Mental models reveal someone's view of how the world works. For example, if you want to get the greatest results with the least effort, you can analyze which actions produce the best results, and then focus your energy on the one or two most powerful actions. Conceptual models are pictures of mental models. Diagrams (often using arrows and labels), maps, and animations visually display systems. Physical models can reproduce the structure/shape and/or material properties of objects, or to show how objects behave. Examples: 1) a clay model of tectonic plates colliding, 2) a scale model of a bridge, or 3) students acting like they are droplets of water, moving around the room as a model for the water cycle. Mathematical models use variables and symbols to represent systems. For example, F = ma F = Force [equals] m = mass [times] a = acceleration This equation can predict how quickly an object will change speeds when a force is applied to it. Equations can be used to create graphs. Computer models are programs that use a set of interrelated equations to model systems. For example, a computer simulation includes all the parts of a car and their material properties. The computer uses equations such as Newton’s laws to calculate the movement of each part during a collision. This helps engineers study the effects of collisions without crashing a real car. Analogies can help students understand relationships between objects. For example, a bicycle chain is an analogy for an electric circuit; there is an energy source and a load and they must be connected in order to work. The goal of science is to capture the most important features that explain the phenomena being studied; not to accurately depict every aspect of nature, Scientists need to focus their attention on key aspects of the system and the variables that are relevant to that process. Students need to understand that models are simplifications. They should be accurate and leave out unimportant aspects. But be aware! For example, while analogies convey key ideas, they can also create unintended misconceptions. Because they are simplifications of complex phenomena, all models have limitations. |