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# Listen Closely!

"Tennessee" Ernie Ford, famed for the hit song "Sixteen Tons," may have found this musical science experiment of great interest!

## Background

Looking at the one-cent coin (penny), a casual observer might assume that it is made completely out of copper. This however isn't true! Although for a brief period of time, at the turn of the 19th century, pennies were made entirely from copper, this coin's composition has changed greatly over the years.  In fact, since 1982 there has been very little copper at all used in the pennies that jingle in our pockets.  Today's pennies are made almost entirely of zinc (97.5%) with only a small amount of copper (2.5%).  This "change" means that the newer pennies are not only lighter than their predecessors, but they also make slightly different sounds.

With this experiment, test your students' ability to hear a difference between the sounds of pennies of different composition.

## Activity

* Note:  This activity is intended for students in 5th grade or higher.

Set up this activity as a science center or a class investigation that will give your students practice at performing a controlled experiment while working together.

Set your students up at a table where they will have relative quiet.  They will need to listen extremely closely to the sounds that the pennies make.  Each lab group will need to have at least 10 pennies (try to give each group at least 5 pennies minted between 1962 and 1982, and 5 pennies that were minted after 1982) and the Penny Sounds lab sheet.

Give your students the following information:
For a long time, pennies were mostly made of copper, but pennies today have very little copper in them.  This change in the coin's makeup also changed the way the penny sounds when it is dropped.  The pennies minted before the formula changed should have a fuller ringing sound to them.  The newer pennies have a more metallic sound.

Have each group listen to the sounds made by dropping each of their pennies.  On their lab sheet, they should record the year each coin was minted, and whether it sounds fuller (F) or more metallic (M).  From the data they collect, the groups should attempt to determine what year they believe the United States Mint changed the penny's composition.

## Extension

• If several groups are conducting this experiment, graph their outcomes to see if there was a general consensus as to when this change was made.
• Allow your students to visit the United States Mint's Web site to see if their results were correct.

## Standards

The project described above reflects some of the national standards of learning as defined by the National Council for the Social Studies (NCSS), the National Council for Teachers of English (NCTE), and the International Society for Technology in Education.  These standards are listed below:

### Science Standards

Science as inquiry:  Students will conduct a scientific experiment and make observations about the composition and sounds of pennies to determine the year in which the penny's makeup was changed.