He Composition of Pennies The US penny has undergone many changes since pennies were first made. In this task, you’ll determine one particular change that was made to the penny around 1982. If you’re unfamiliar with balances and scales or graduated cylinders, read Lab Instruments and Measurements before beginning.

If you’re using an Edmentum lab kit, remove the electronic balance and graduated cylinder from the bag labeled Common Materials. These materials are italicized in the following equipment list. Then gather any additional items shown on the list. If you’re not using an Edmentum lab kit, alternatives have been suggested in parentheses. If you don't have these alternative materials at home, please check with your teacher for help.

You’ll need these materials:

electronic balance, precise to at least 0.1 g (may also use a kitchen scale)
graduated cylinder (may also use a 1-teaspoon measure)
at least 20 pennies; at least 5 of them dated before 1982, and at least 5 dated after 1982
a narrow, transparent container that can hold water; the narrower the better, as long as pennies will fit into it
masking tape
Part A
Separate the pennies you have into two groups: one group with pennies dated before 1982 and the other with pennies dated after 1982. Compare the two groups. Record any similarities or differences in size or appearance that you notice between the two groups.

Part B
Gather all of your pennies dated before 1982. Then follow the steps to complete the table. Include units as necessary.

Record the number of pennies dated before 1982.
Weigh (as a group) the pennies dated before 1982. Record the total mass. If you’re unfamiliar with using an electronic balance, watch this video before continuing.
Calculate and record the average mass of a single penny. If you need help with the calculation, visit the averaging data section of the math review.

Part C
Now gather all of your pennies dated after 1982. Complete the table for the post-1982 pennies using the same steps from part B.

Part D
In parts B and C, you measured the average mass of each group of pennies. Now you’ll measure their volume. (For this part, assume that the pennies dated before and after 1982 have the same volume.) Follow the steps to complete the table. If you’re planning to use a graduated cylinder, watch this video on measuring volume before continuing.

Stay safe! Be careful when handling glass containers so they don’t break.

Add water to the narrow transparent container until it is about half full.
Stick a piece of tape to the outside of the container to mark the water level. The water level must be even with the top edge of the tape.
Using a graduated cylinder or a teaspoon measure, add another 5 mL (1 teaspoon) of water to the container. Be sure your measurement is exact.
Stick another piece of tape to the outside of the container to mark the new water level. This time, the water level must be even with the bottom edge of the tape. Your setup should look something like this.
Next, remove 5 mL (1 teaspoon) of water from the container. The water level will again be even with the top edge of the bottom piece of tape. (Alternatively, pour out all the water from the container and refill it to the top edge of the bottom piece of tape.)
Add pennies one at a time until the water level is even with the lower edge of the top piece of tape. In the table, record the number of pennies added. The pennies you added just displaced about 5 mL of water.
Divide 5 mL by the number of pennies added to determine the average volume of each penny. Record this value in the table.

Part E
In part E, you’ll use your answers from parts B, C, and D to find the average density of each type of penny. Recall that density is mass divided by volume:

D = .

Question 1
Calculate the average density of a penny (in g/mL) made before 1982. Show your work.

Question 2
Now calculate and record the average density of a penny (in g/mL) made after 1982. Show your work.

Question 3
Study the densities of the metals in the table below. Based on your experimental data, which metal was likely used to make the pre-1982 pennies? Describe what led you to this conclusion.

Metal Density (g/mL)
aluminum 2.70
titanium 4.50
zinc 7.14
iron 7.87
copper 8.92
silver 10.49
lead 11.34
gold 19.3