# III Modeling Phases: Modify Model

The goal of this modeling phase is to have the class modify the model to help it provide a better explanation for the phenomenon.

What characterizes this modeling phase is that the focus of classroom activity is on modifying aspects of the model that students have evaluated as needing improvement. There are a number of Level II Creative Reasoning Processes that can help with this modeling phase.

This phase can rapidly alternate with the Evaluating a Model phase and these two phases can work together to support Level IV classroom modes. However, at times a teacher may want the class to focus on modifying. In the first example below, the teacher directly challenged the class to come up with a modification to solve a question she had about the model. In the second example, the class had gone through an extensive evaluation phase where they had decided that many aspects of the models currently on the board were problematic. At a certain point, the teacher decided to call a halt to the evaluation of those flawed elements and did so by erasing them. He then challenged the students to come up with some different ideas

 Example 1 When modeling the lungs, after considerable discussion and help from their teacher, 8th graders had evolved a model with tubes that took air to many cavities (alveoli). In the cavities, air was near to blood vessels (capillaries). The teacher then challenged them, “But how does oxygen get into the blood vessels from the cavities?” This was a direct request for model modification.         Two ideas proposed for modification were “little pipes” from the alveoli to the capillaries (pictured) and “oxygen...seeping through the walls.” These were each evaluated, returning to the Model Evaluation Phase in cyclical fashion. a. Model of lungs with tubes to many alveoli. "But how does oxygen get into the blood vessels?" b. One idea: Model of alveoli with "little pipes" to a capillary.
 Example 2 (Fig. a) Students had evaluated two possible models for the human circulatory system. (See Model Competition Example 1). As a result of their evaluation, they had decided that neither model worked. The teacher suggested erasing all the connections that differed between the two models. For the Model Modification phase, the class began to suggest new ideas for how the lungs might be connected to the heart and how the blood might return from the cells of the body to pick up more oxygen.       (Fig. b) After an extensive Model Modification phase, the resulting model had a two loop system.       (Fig. c) One final modification occurred when a student spontaneously walked to the front of the room and erased holes between the upper and lower chambers of the heart, providing a complete, complex pathway for the blood through the entire system.   Although this part of the discussion was focused on modification, there was actually a frequent back and forth between modification and evaluation, as each new model element was evaluated before the class agreed to add it. These included three blood vessels, the color codes for each (to determine oxygen rich or poor), designations as arteries or veins (determined by whether they travel away from or to the heart, not whether they are oxygen rich or poor), vessels inside the lungs, and finally the valves inside the heart. This discussion used several Level II strategies to support Model Modification, in particular, Adding or Subtracting Model Elements. a. Model at beginning of modification phase. b. Model after many modifications. c. Model after the final modification. Note the holes between the upper and lower chambers of the heart; the route the blood takes through the chambers can now be seen clearly.

Supporting and Contributing Strategies

Reasoning processes and strategies that support this phase of the modeling sequence are found in:

Suggestions for managing a type of discussion that can be very useful here are included under:

There are many Visualization strategies that may be helpful. Among them:

Background

A discussion of this modeling phase in the context of a classroom example is in Core of this Approach.

For how this phase fits into the larger framework, see the Level III section of the Educator's Tour.

For more discussion on the theoretical underpinnings of the framework, see the Introduction to the Full Theory page.

Articles, Papers and Websites

More in-depth discussion of this modeling phase is found in the following paper by our team:

Large scale scientific modeling practices (Nunez-Oviedo & Clement, 2019)