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Nature of Science

Performance Benchmark N.12.A.5
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Nature of Science
Scientific Inquiry


Science, Technology, and Society
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know models and modeling can be used to identify and predict cause-effect relationships.  I/S

Scientists spend a great deal of time building, testing, comparing and revising models.  According to Cartier, Rudolph, and Stewart, “modeling scientific concepts serve several purposes.  The most important overall goal of scientists is the development of an understanding of how the natural world works. In all scientific disciplines, this understanding is most often accomplished through the conceptualization of models of various natural processes.”  (

A simple definition of a scientific model is a set of ideas that describes a natural process.  Models can be used to illustrate complex concepts making them more tangible. For example, models are used when explaining abstract concepts such as the Krebs cycle or the carbon cycle.  Models also allow scientists to interact with objects too small, large, distant or otherwise inaccessible. For example, models work well to explain microorganisms, the surface of other planets, and atoms/molecules.  Models are also used to visualize forces such as gravity, energy, and magnetism which cannot be seen, but scientists can model their effect on matter.

Models can be divided into two categories: working models and representational systems.  A working model is also called a hypothesis.  This “working model” is refined through experimentation and data analysis (Figure 1).  A model can also be a representational system which includes maps, diagrams, physical models, and mathematical models. Science is an ever changing process and models are only as accurate as the current scientific knowledge. Therefore, models must be evaluated and modified often.


Figure 1. Diagram A depicts the simple flow of the scientific method. Diagram B shows how the same process is used to generate a model. (from

Working Models (hypotheses)
The definition of a hypothesis is difficult for students to understand.  When asked, students often rotely respond that a hypothesis is an “educated guess”.  This is an overly simplified definition that is often used by teachers. A better definition for students is to describe a hypothesis as a “working model” (Figure 1).  Based on current data, scientists develop a working idea of how a system works. Scientists then use this working model to predict cause and effect relationships and design experimentation to test the working model. Finally, scientists revise or accept the working model based on their results.  Students will recognize this process as the scientific method. The definition of a hypothesis as a working model rather than an “educated guess,” enables students to apply the term in more situations.

Figure 2. The human circulatory system.

The simple definition of a scientific model is a set of ideas that describes a natural process.  For example, the circulation model in human anatomy illustrates the cellular level to system level that covers the chemistry, physics, and biology of how and why blood moves around the body (Figure 2).

Further detail about the circulatory system can be found in the TIPS Benchmark L.12.B.2.

Representational Systems

Physical Models
A majority of people are familiar with physical models because they have been using them their entire lives. For example, many individuals played with Legos, blocks, toy cars, and Barbies as children. Scientists often build physical representations to have a tangible, manipulatable example of what they are studying.  These representations allow scientists to “see” things that are difficult to observe.  For example, when constructing a model of a virus (Figure 3) and a cell (Figure 4), a scientist can investigate the relationship between the two components by manually manipulating the models.  Physical models can be built to represent a variety of scientific ideas from planetary systems to atomic structure. As new information and evidence becomes available, models are modified to fit new parameters defined by experimentation.  The model of the sun, Earth, and moon in Figure 5 was constructed in 1712 by John Rowley based on the information available at the time. Visit for instructions on how to construct a scale model of the sun, earth, and moon based on current data.

Rowley's original orrery, 1712-13.

Figure 3. A model of  HIV enlarged 1,000,000 times. (from
88/ library/Models/Models/
1685_ H6A288_1996.jpg

Figure 4. A model of an animal cell magnified 12,000 times. (from

Figure 5. A model of the sun, earth and moon constructed in 1712. (from http://www.sciencemuseum.
10197368. aspx

Physical models in two dimensions are called diagrams.  Diagrams include labeled schematics of physical objects and flow charts to illustrate a complex process.  A pictorial display is a tool that allows the reader to visualize cause and effect relationships between physical parts or a process. See Figure 6 for examples of diagrams.

Figure 6. Several examples of diagrams.
Phylogeny for Life
(from Biology_203/Summaries/Phylogeny.htm)

Free Body Diagram
Phys160/ Ftest2.jpeg

Complex Electrical Circuit

A mathematical model is a model that uses mathematical language as an abstract representation of a scientific concept.  The model predicts the behavior of a system within a given set of assumptions. Therefore, you must know the parameters of the mathematical model before applying it to a new situation. 

Figure 7:  The Hardy-Weinberg Equations.

p   +   q   =   1

p2  +  2pq   +   q2  =  1

p = frequency of one of two alleles
q = frequency of the other allele

There are many mathematical models in science. One example is the Hardy-Weinberg equilibrium model which consists of two equations that work in tandem to predict genotypic and allelic frequencies in a population (Figure 7).  Knowing the frequency of one of the two alleles in a population, you can predict the frequency of the other. You can also predict what would happen to the system when one frequency is changed. This equation was formulated in the early 1900s. This model was developed over time through careful experimentation and modified as needed.  A set of assumptions and exclusions were also developed to refine the situations where the model was applicable. 

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Performance Benchmark N.12.A.5

Students know models and modeling can be used to identify and predict cause-effect relationships.  I/S

Common misconceptions associated with this benchmark:

1. Students incorrectly believe that a model is static.

Any designed model must be flexible to allow the addition of newly discovered items or relationships. For example, the reclassification of Pluto has changed the model of our solar system. Models change as more information is discovered.

 2. Students incorrectly believe that there is only one accepted model per concept.

Many models may be designed to explain a phenomenon using the same data set to meet the needs of the user.  One scientist may be interested in macro level relationships while another may design a model that shows micro level relationships.  Therefore, a model may be extremely simple or very complicated when more specificity is needed.

3. Students inaccurately believe models always make accurate predictions.

“We can make predictions for simple systems more easily than for complex systems. It is very difficult to predict the evolution of a complex system far into the future. An example of this is the accurate prediction of weather. In order to update their models, meteorologists must constantly monitor and update parameters such as temperature, pressure, humidity, wind, solar radiation, etc.”  

For additional common misconceptions about science visit

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Performance Benchmark N.12.A.5

Students know models and modeling can be used to identify and predict cause-effect relationships.  I/S

Sample Test Questions

1st Item Specification:  Describe how models are used in science.

Depth of Knowledge Level 1

  1. Which of the following is NOTa reason for using models in science?
    1. Visualize objects too small, large, or distant to see.
    2. Predict cause and effect relationships.
    3. Provide a working hypothesis.
    4. To construct a final representation of object studied .
  1. All models must NOT
    1. be accepted by all scientists working in field.
    2. be supported by experimental data.
    3. evolve as new data is analyzed.
    4. show relationships between components.

Depth of Knowledge Level 2

  1. Use these two models of the atom to answer the following question.

    The model of an atom was modified because scientists
    1. only look at the data that is important to science to create a model.
    2. work in different fields of science and draw conclusions from that expertise resulting in differing models.
    3. used new evidence to support the change in the working hypothesis.
    4. must considers how their government will react to the explanations.
  1. Models are often made to simplify a very complex concept.  Why is it difficult to construct a single model for life on Earth?
    1. Many organisms live in habitats that are difficult to explore.
    2. Life on Earth is so diverse that it is difficult to understand the complexity.
    3. Tropical rain forests contain so many species that it is not possible to find them all.
    4. Many organisms are microscopic and therefore are difficult to observe.

2nd Item Specification:  Use models and modeling to illustrate relationships and predict outcomes.

Depth of Knowledge Level 1

  1. The diagram below contains three molecules.

    The following four diagrams show these molecules joined together.

    Predict a model of how these molecules would join together.
    1. Diagram 1
    2. Diagram 2
    3. Diagram 3
    4. Diagram 4
  1. The diagram below is a model of the pressure/temperature relationship and the resulting phase of water.


    Predict the phase of water at a temperature of 750C and a pressure of 300 millibars.
    1. Solid
    2. Liquid
    3. Vapor
    4. Plasma

Depth of Knowledge Level 2

  1. The following diagram is a simple food web.

    If the Corn and Oats were removed from the food web above, which of the following will be MOST affected?
    1. Mice and Rats
    2. Hawks and Owls
    3. Snakes and Raccoons
    4. Grasshoppers and Crickets
  1. The map below shows a portion of California along the San Andreas Fault zone.  The map shows the probability that an earthquake strong enough to damage buildings and other structures will occur between now and the year 2024.

(Diagram from ExamGen 4.3)

    The state of California wants to build a nuclear reactor to meet its future energy needs.  Using the model above, where would be the BEST location to place the nuclear reactor?
    1. San Diego
    2. Bakersfield
    3. Los Angeles
    4. Barstow

3rd Item Specification:  Evaluate the appropriateness of a model.

Depth of Knowledge Level 1

  1. Which of the following models would be the BEST model choice to visualize the relative positions of the planets in our solar system?
    1. Full scale physical model
    2. Mathematical model
    3. Working hypothesis
    4. Two dimensional diagram
  1. Which of the following models would be the BEST model choice to predict changes in a system?
    1. Full scale physical model
    2. Mathematical model
    3. Working hypothesis
    4. Two dimensional diagram

Depth of Knowledge Level 2

  1. The model below is set up to show how a lunar eclipse occurs.

    What is the greatest limitation of this model?
    1. The light bulb is standing straight up instead of tilted on an axis.
    2. Comparative sizes and distances are inaccurate
    3. The shadow is being cast in the wrong direction
    4. The heat released is much less than that released by the Sun.
  1. Below is a flow chart showing the types of data used to construct a global climate model.


    Which of the following is NOT a limitation of the global climate model used to support the concept of global warming?
    1. Current computer technology is incapable of processing the amount of data collected in a timely manner so the data must be minimized to draw conclusions.
    2. The model assumes that past climate patterns will continue in the future.  Therefore, we are using past data to predict future weather patterns.
    3. The lack of scientific researchers working on the global warming model limits the rate of which the data can be processed to develop hypotheses.
    4. The model assumes a cause and effect relationship between carbon dioxide and temperature which may or may not be true.

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Performance Benchmark N.12.A.5

Students know models and modeling can be used to identify and predict cause-effect relationships.  I/S

Intervention Strategies and Resources

  1. D, DOK Level 1
  2. A, DOK Level 1
  3. C, DOK Level 2
  4. B, DOK Level 2
  5. A, DOK Level 1
  6. C, DOK Level 1
  7. A, DOK Level 2
  8. D, DOK Level 2
  9. D, DOK Level 1
  10. B, DOK Level 1
  11. B, DOK Level 2
  12. C, DOK Level 2

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Performance Benchmark N.12.A.5

Students know models and modeling can be used to identify and predict cause-effect relationships.  I/S

Intervention Strategies and Resources

The following list of intervention strategies and resources will facilitate student understanding of this benchmark.
1.  Science NetLinks: Evaluating Mathematical Models
This website “uses the Internet to evaluate a variety of mathematical models.  Because mathematics plays such a central role in modern culture, scientifically literate students must develop a basic understanding of the nature of mathematics. It is important for students to realize that mathematics, like science and technology, incorporates both finding answers to fundamental questions and solving practical problems.”

To access these activities, go to

2.  FORSEA: If I Can’t See It, How Do I Know It’s There?
This lesson has students constructing a model of the ocean floor using a closed shoe box with a lid with holes spaced in a 1cm grid.  Students use bamboo skewers to assess the shapes in the box and transfer their data into a topographic model.

This activity can be found at

3.  My NASA Data Lesson: Interpreting CERES Cloud Data and Weather Maps
This lesson asks students to correlate a satellite image with satellite data collected over the United States during a winter storm.  This activity is appropriate for students who are capable of cross referencing several sources of data.  Students also need to be proficient in working with latitude and longitude coordinates.  This activity can be modified to meet the needs of your students.

To link to this activity, go to

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