Key Idea: Models are useful for thinking about real-world objects, events, and processes.

Students are expected to know that:

  1. Someone may use a model to think about (i.e. to visualize or imagine and to reason with or reflect upon) objects, events, and processes in the real world (phenomena).
    • Objects: Earth (how much is covered by land vs. water), Moon (how cratered it is), Sun, Earth-Moon-Sun System (relative sizes, relative distances, etc.)
    • Events: Eclipse, Earthquake, tsunami, car crash, election, battle
    • Processes: erosion, presidential campaign, chemical reaction, car assembly, plant growth
  2. Use of models makes it possible to observe phenomena that would be difficult or impossible to observe in the real world. For example, a phenomenon could happen very slowly, very quickly, on a very small scale, or on a very large scale. The phenomenon could also be too complex, too expensive, or too dangerous to observe directly.
  3. Use of models makes it possible to illustrate abstract aspects of a phenomenon (e.g. arrows to represent forces).
  4. Use of models makes it possible to ignore some features of a phenomenon being considered so that there is less to keep track of. This allows the exclusion of features that are believed to be irrelevant in how the phenomena behave (e.g. food web diagrams do not show how predators catch and consume their prey, point masses in a physics problem do not show the actual size and/or shapes of the objects they represent). Whether or not a given feature turns out to be irrelevant depends upon the purpose of the model and how well understood the phenomenon is.
  5. A model may be modified as it is being used based on new information about the phenomenon it represents or based on new thinking about what features of the phenomenon are important to represent in the model.