What is a Model Description?

What is a Scientific Model?

A model of nature is a description of predictable patterns in the

• • structure (how nature/matter/a system is organized) and

  • behavior (what it does, how it changes)

of some part of nature. A model allows us to look at a given system and reliably

• • describe the current state or structure of the system,

  • explain connections and behaviors we observe, and

  • predict how it might change.

Such a model is often called a conceptual model, because it communicates our understanding of nature rather then just a description 'what it looks like' (which we might call a physical model).

Creating a conceptual/scientific model is a way of clearly communicating how we understand nature in a manner that allows us to test and refine our understanding, and then come to consensus on the model as a community. The model makes the connections and patterns visible to everyone so we can more easily discuss the strengths and weaknesses of our understanding of nature.

A scientific model is typically communicated using four modes of representation:

• • graphs (bar, x-y, scatter, pie charts, etc.)

  • diagrams (particle diagrams, flow charts, organizational diagrams, force diagrams, motion maps, etc.)

  • mathematical expressions (equations, proportional statements, ratio relationships, product relationships)

  • verbal descriptions (sentences expressing organization or behavior)

All representations of the model should complement each other by expressing the same behavior or structure across the different representations (see the example of the constant velocity model you developed in physics below).

What is a Model Description for this course?

A good model typically has a small number of key ideas, appropriately represented, that allow the model users to describe a system and make predictions about its behavior and/or structure.

The model description would include verbal descriptions of each key idea, coordinated with appropriate graphs, diagrams, and/or mathematical expressions that also describe the same key ideas.

Below is an example of a Model Description from physics: an object moving a constant velocity (the Constant Velocity model).

Notice in the physics model example above (a model with only behavioral information), the pattern of equal displacement for equal time intervals is expressed in all four representational modes (verbal, graphical, diagrammatic, and mathematical). All four representational modes say the same thing about the object's behavior, with each mode giving a useful tool for understanding constant motion and predicting how the object's place in space will change across time.

So...in chemistry our model description would include:

• Structural information (often a microscopic view):

  • verbal description(s) of how matter is structured (what kind of particle are we using? what features does the particle have?), coupled with

  • diagrams showing that same structure of matter ("particle diagrams")

• Behavioral information (micro- and/or macroscopic view):

  • verbal description(s) of patterns in how matter changes (temperature, states, substance...), coupled with

  • diagrams, graphs, and/or mathematical expressions showing the same patterns of change.