DENSITY OF PENNIES LAB

Before 1982, pennies were made of a copper alloy. Since then, they have been made with an outside coating of copper and an inner core of a different metal. In this experiment, you will determine the density of post-1983 pennies. Then, you will use known density values to identify the metal used in the core of these pennies.

MATERIALS

Density of Pennies Lab (Inquiry)ICP

  • post-1983 pennies (need 25)
  • 50 or 100-mL graduated cylinder
  • digital scale
  • beaker of water
  • eyedropper

Density of Pennies Lab (Inquiry)ICP

PROCEDURE

  1. Determine the mass of 5, 10, 15, 20, 25 pre and post 1983 pennies using the digital scale. Record your values.
  2. Measure 50 mL of water into the graduated cylinder. You may find that using an eyedropper is helpful for making final adjustments in the level.
  3. Using your post-1983 pennies, gently add them to the cylinder in increments of 5, measuring the volume each time. Record your values.
  4. Subtract the volume of the water and the pennies from the volume of the water to get the volume of the pennies.
  5. Repeat step 3 with your pre-1983 pennies.

DATA

Prepare a data table to display your measurements. The data table should be recorded in each member’s lab notebook. A sample of the data is below.

A / B / C / D
Pennies / Mass / Volume (pennies +water) / Volume pennies (C-original vol of water)
Post-1983 - 5
Post-1983 – 10
Post-1983 – 15
Post-1983 – 20
Post-1983 - 25

ANALYSIS

  1. Calculate the density of the pre and post 1983 pennies.
  2. Using an excel spreadsheet, graph the mass (set up in front of the room), volume and density of post-1983 pennies. What do you notice about the mass, volume and density lines?

CONCLUSIONS

Write a conclusion that answers the following questions.

  • Based on your calculated density and the table below, which metal do you think is used in the core of post-1983 pennies? Explain your choice.
  • The actual density of post-1983 pennies is 7.05 g/cm3. How close was your calculation? Use the formula:

Difference between your results and the known result

Known results x 100

  • Discuss possible sources of error and how you could improve your procedure in the future.

Metal / Density (g/cm3)
magnesium
aluminum
zinc
copper
silver
lead / 1.74
2.70
7.00
8.92
10.50
11.35

Density of Pennies Lab (Inquiry)ICP