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Did you ever read a road map like this one? Maybe not, but you’ve probably made a sketch of a house or other object and played with toy cars or dolls. What do all these activities have in common? They all involve models.

What Is a Model?

A model is a representation of an object, system, or process. For example, a road map is a representation of an actual system of roads on the ground. Models are very useful in science. They provide a way to investigate things that are too small, large, complex, or distant to investigate directly. To be useful, a model must closely represent the real thing in important ways, but it must be simpler and easier to understand than the real thing.

Q: What might be examples of things that would be modeled in physical science because they are difficult to investigate directly?

A: Examples include extremely small things such as atoms, very distant objects such as stars, and complex systems such as the electric grid that carries electricity throughout the country.

Q: What are ways that these things might be modeled?

A: Types of models include two-dimensional diagrams, three-dimensional structures, mathematical formulas, and computer simulations. Examples of simple two-dimensional models in physical science are described below. You can see examples of other types of physical science models at these URLs:

Simple Models in Physical Science

The Figure below is a simple two-dimensional model of a water molecule. This is the smallest particle of water that still has the properties of water. The model shows that each molecule of water consists of one atom of oxygen and two atoms of hydrogen.

Q: What else can you learn about water molecules from this model?

A: The model shows the number of atomic particles—protons, neutrons, and electrons—in each type of atom. It also shows that each hydrogen atom in a water molecule shares its electron with the oxygen atom.

Q: Do you think this water molecule model satisfies the criteria of a useful model? In other words, does it represent a real water molecule in important ways while being simpler and easier to understand than a real water molecule?

A: The model shows the basic structure of a water molecule and how the atoms in the molecule share electrons. These features of the water molecule explain important properties of water. The model is also simpler and easier to understand than a real water molecule. In a real molecule, electrons spin around the nuclei at the center of the atoms in a cloud, rather than in neat, circular orbits, as shown in the model. The atoms of a real water molecule also contain even smaller particles than protons, neutrons, and electrons. For many purposes, however, it’s not necessary to represent these more complex features of a real water molecule.

The Figure below shows another example of a simple model in physical science. This diagram is a model of an electric circuit. It represents the main parts of the circuit with simple symbols. Horizontal lines with + and – signs represent a battery. The parts labeled R 1 , R 2 , and R 3 are devices that use electricity provided by the battery. For example, these parts might be a series of three light bulbs.

Q: In the electric circuit diagram, what do the black lines connecting the battery and electric devices represent?

A: The black lines represent electric wires. The wires are necessary to carry electric current from the battery to the electric devices and back to the battery again.

Q: How is a circuit diagram simpler and easier to understand than an actual electric circuit?

A: A circuit diagram shows only the parts of the circuit that carry electric current, and it uses simple symbols to represent them.


  • A model is a representation of an object, system, or process that is simpler and easier to understand than the real thing.
  • Examples of simple models in physical science include two-dimensional models of molecules and electric circuits.


  • model : Representation of an object, system, or process.


Follow the instructions at this URL to make a model of an atom.



  1. What is a model?
  2. Why are models useful in science?
  3. Identify characteristics of a good model.
  4. Describe a simple model in physical science.

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7 , 8

Date Created:

Oct 31, 2012

Last Modified:

Jul 28, 2014
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