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# ZingPath: States of Matter

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## States of Matter

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### Lesson Focus

#### The Thermal Expansion of Metals

Physical Science

In this experiment, you will investigate the factors that affect thermal expansion.

### Now You Know

After completing this tutorial, you will be able to complete the following:

• Define thermal expansion as an increase in the size of an object due to an increase in temperature.
• Explain that different materials will expand by different amounts when heated.
• Explain that the expansion of metals increases as the applied heat increases.

### Everything You'll Have Covered

Thermal expansion is an increase in the size of a material when it is heated, but what exactly is expanding? These materials are made out of molecules that are situated relatively close to one another when cool. As the molecules within the material are heated, they begin to move faster and further apart from one another. As they separate, the material begins to expand to account for the greater movement and space between molecules. As the temperature of the material begins to decrease, the molecules move closer together because they are moving slower. This results in the material returning back to its original state.

As these molecules found within the material are heated and cooled, they expand and contract in all dimensions. For almost all instances, scientists and engineers focus on two main types of expansion: linear expansivity and volume expansivity. Linear expansion refers to a material expanding in only one direction. Volume expansion refers to the expansion of a material in all three dimensions. The choice of which measurement to use is a practical one. For example, determining the difference in the length of telephone wire on a hot day as opposed to a cold day may be significant. The wire will expand in all three dimensions, but only the linear expansion is of importance in this situation. On the other hand, if one wants to know how much a balloon will expand as the heat applied increases, the answer is determined by knowing the volume expansion of the gas used inside of the balloon.

Many of our everyday activities revolve around continuously expanding and contracting objects such as telephone wires, buildings, bridges, etc. For scientists and engineers, knowing the varying expansion and contraction measurements of such objects keeps us in a world that is safe for travel, shelter, and communication.

### Tutorial Details

 Approximate Time 20 Minutes Pre-requisite Concepts Students should be familiar with matter, energy, and angles. Course Physical Science Type of Tutorial Experiment Key Vocabulary aluminum, angle, Bunsen burner