PENNY DENSITY LAB
(Don’t Copy) Backgound: In this lab, you will determine & 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 US Mint changed the
composition of pennies. Before 1982, the composition of a penny was 95% copper and 5% zinc. This formula remained
until 1982, when the composition became 97.5% zinc and 2.5% copper (copper-plated zinc). Cents of both compositions
appeared in that year.
(Copy) Purpose: Our job is to determine the density of both sets of pennies & compare them.
(Copy) Hypothesis: Write your own hypothesis based on the purpose of the lab.
(Copy) Materials: 8 pre-1982 pennies (Penny Set A); 8 post-1982 pennies (Penny Set B), 50 or 100 mL graduated cylinder;
water, scale
(Copy) Procedure: (Paraphrase the following steps in your own words so someone else could follow your work.)
1. From Penny Set A, measure the mass of 1 penny and record in data table. Then measure the mass of 2 pennies and
record: 3 pennies and record, 4 pennies, 5 pennies, 6 pennies, 7 pennies , 8 pennies.
2. Repeat the Procedure 1 for Penny Set B.
3. Using a 50-mL or 100-mL graduated cylinder, measure the volume of 1 penny from Penny Set A. 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 Procedure #3 for Penny Set B.
(Copy) Data:
Mass of weighing container: __________
Set A (pre-1982 pennies)
# of
pennies
Mass of
pennies in
grams
(y)
1
2
3
4
5
6
7
8
Volume of
water
before
pennies
added
Volume of
water after
pennies
added
Set B (post-1982 pennies)
Volume of
pennies in
mL
Mass of
pennies in
grams
(x)
(y)
Volume of
water before
pennies
added
Volume of
water after
pennies
added
Volume of
pennies in
mL
(x)
Analysis & Conclusion:
1. How are the pre-1982 and post-1982 pennies different from each other?
2. How is the density of copper different from the density of zinc?
3. 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?
(COMPLETE STEPS #4-7 ON GRAPH PAPER, THEN ATTACH TO REPORT)
4. Using graph paper, create a graph of your data (mass v. volume). Plot the points (volume, mass) as (x, y) . You will
have two lines on your graph (Line A-pre-1982 and Line B-post-1982). Distinguish between the two sets of data on
your graph. Your graph should include:
a. Descriptive Title
b. Labeled x & y axes (tell what each axis represents.)
c. Appropriate data intervals. (for example, if your measurements are 0.2, 1.4, & 3.5, the range on your axis
might start at 0.0 and end at 4.0. Your intervals might be 0.2 units apart.)
d. A key that explains the meaning of each of the two lines.
5. Draw a straight line that “best fits” the 8 points plotted for the Set A penny data. (This is called a line of “best fit.”)
Do NOT connect the dots!!!
6. Complete step 6 for the Set B penny data.
7. Pick 2 points on Line A (one towards the bottom and one towards the top) and label each point with their correct
(x,y) values.
8. Calculate the slope of each line and include units. Show all work in your lab notebook. (slope = change in y
change in x)
9. Repeat steps 8 & 9 for Line B.
10. What is the density of the Set A (pre-1982) pennies? Of the Set B (post-1982) pennies?
11. Which set of pennies is more dense?
12. Was your hypothesis supported or rejected by the data?
13. How would the density of 10 pre-1982 pennies compare to the density of 20 pre-1982 pennies? Explain your
answer.
14. If you had a penny and the date was unreadable, how could you determine if it was minted before or after 1982?
15. 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.