Penny Density Lab
Background Information
An old riddle asks “Which is heavier, a pound of feathers or a pound of lead?” You know that a pound of
feathers and a pound of lead both weigh the same, one pound. However, you also know that there is something
very different about a small lead brick and a large bag of feathers, even though they weigh the same. The key to
answering the riddle is understanding the relationship that exists between a substance’s mass and the volume it
occupies. This relationship is expressed by the physical property called density. Density is defined as the ratio of
a substance’s mass to the volume it occupies.
Density = mass of substance (g)/volume of substance (mL)
In this lab, you will determine and compare the density of two sets of pennies by graphing mass vs. volume.
Penny Set A was minted before 1982. Penny Set B was minted after 1982. In 1982, the U.S. Mint changed the
composition of pennies. Before 1982, pennies were made entirely of copper. After 1982, pennies were made of
zinc with a copper coating.
Purpose Statement: What is the purpose of this lab? (Write this in your lab notebook)
Questions:
1.
2.
3.
4.
5.
How are the pre-1982 and post-1982 pennies different from each other?
How is the density of copper different from the density of zinc?
What instrument will you use to measure the mass of the pennies?
How will you determine the volume of the pennies?
It is important for the pennies to be dry before the mass or volume is determined. Suppose you found the
mass of wet pennies. Would the density be too high or too low?
Hypothesis
Write a hypothesis based on the purpose of the lab. Include an explanation for your prediction.
Procedure
Do NOT mix the contents of the two sets of pennies!!! Always start with DRY pennies before
you take the mass and volume measurements.
1.
From Penny Set A (Pre-1982), measure the mass of 1 penny and then of 2, 3, 4, 5, 6, 7, and 8 pennies. Do not
drop the pennies onto the balance. Record all the mass measurements for Penny Set A.
2. Repeat the procedure for Penny Set B (Post-1982). Record all the mass measurements for Penny Set B.
3. Using a 50-mL or 100-mL graduated cylinder, measure the volume of 1 penny from Penny Set A (Pre-1982).
Then, find the volume of 2, 3, 4, 5, 6, 7, and 8 pennies. Record all the volume measurements for Penny Set A.
4. Repeat the procedure for Penny Set B (Post-1982). Record all the volume measurements for Penny Set B.
Data Table
DRAW THE DATA TABLE IN YOUR LAB NOTEBOOK!!!!!!
Fill in the # Pennies you will use and the measurements you will make for each set.
# of Pennies
Set A (Pre-1982)
Set B (Post-1982)
Data Analysis/Conclusion:
5. Using graph paper, create a graph of your data (mass vs. volume). Attach your graph to your lab report. Use
the same graphing procedure you learned in Discovery 1-3. You will have two lines on your graph (A—Pre1982 and B—Post-1982). Distinguish between the two sets of data on your graph. Your graph should have:
correct data intervals labeled axes w/units best-fit lines descriptive title key or method to distinguish both
lines
a. Pick two points on each best-fit line (one towards the bottom and one towards the top). Label all
four points with their correct (x, y) values.
b. Calculate the slope of each line and include units. Show your work in your lab notebook.
Set A (Pre-1982)
Set B (Post-1982)
6. What is the density of the A (pre-82) pennies? Of the B (post-82) pennies?
7. Which set of pennies (Pre-1982 or Post-1982) is more dense?
8. Restate your hypothesis (just the prediction part).
9. Was your hypothesis supported or rejected by the data?
10. How would the density of 10 pre-1982 pennies compare to the density of 20 pre-1982 pennies? Explain your
answer.
11. If you had a penny and the date was unreadable, how could you determine if it was minted before or after
1982?
12. Think of another example in the world where determining the density of a substance would be useful in
identification. Describe the situation and why density would be important in the identification. (Points for
creativity. You will not get full points if you copy another student's answer).