Density of Penny Lab

Name: ______Date:______Period:______

Density of Penny Lab

Background:

Originally, American pennies were made of 95% copper. In the late 1970’s the price of copper rose so dramatically that Congress feared the copper content in pennies would be more valuable than one cent and that people would hoard the copper coins and melt them down and sell the copper. Consequently, a bill was proposed in Congress to reduce the copper content of pennies. In this activity, you will use the water displacement method to determine if Congress passed the bill and put it into effect. Use 20 pre-1982 U.S. pennies and 20 post-1982 pennies (do not use the 1982 pennies). Determine the mass of both sets of pennies. Determine the volume of each group by the method of water displacement. Calculate the density of the pre-1982 and post-1982 pennies to determine their composition.

Materials:Balance, Pre-1982 pennies, Post-1982 pennies, 50mL graduated cylinder, computer w/ Excel

Procedure:Always start with DRY pennies before you take the mass and volume measurements.

1. Open “Density of Penny Lab Spreadsheet” by visiting clicking on your course name on the sidebar, and scrolling down to today’s date.
2. Find the mass 5 pre-1982 pennies and record below. (Find the mass of all 5 at the same time)
3. Find the volume of 5 pre-1982 pennies via water displacement. Don’t forget about sig figs!!
4. Enter your data into the Excel spreadsheet.
5. Repeat for 10, 15, and 20 pre-1982 pennies.
6. Repeat for 5, 10, 15, and 20 post-1982 pennies.

Data:

Calculations: Round your answers to the correct number of significant figures.

1. Slope for the pre-1982 pennies: ______

1. Slope for the post-1982 pennies: ______

1. Density of a pre-1982 penny: ______

1. Density of a post-1982 penny: ______

Analysis: Write answers in complete sentences. Use a separate sheet if you need more space. Remember: You can talk about the questions in your group, but it should not be identical.

1. On the basis of your results, does it appear that the bill was enacted? Use data from the lab to justify your answer.

1. Based on your calculated density and the table to the right, which metal do you think is used in the core of pre-1982 pennies? Explain your choice.

1. Based on your calculated density and the table above, which metal do you think is used in the core of post-1982 pennies? Explain your choice.

1. Explain why your values do not exactly match those in the metal/density table.

1. If you had a penny and the date was unreadable, how could you determine if it was minted before or after 1982?

Complete the following calculations. Don’t forget about sig figs and show work! 

1. If 30.943 g of a liquid occupy a space of 35.0 mL, what is the density of the liquid in g/mL?

1. The density of lead is 11.342 g/mL. What would be the volume of a 2.0 x103 kg sample of this metal?

1. What is the mass of a 350 cm3 sample of pure silicon with a density of 2.336 g/cm3?