General Chemistry
Name:___________________________
Penny Density Lab
Date:____________________Hour:______
COMMON LAB ACTIVITY 1: Measuring the Density of Pennies
*Learning Target Met: Identify the difference between physical and chemical properties/changes.
Use proper measurement techniques and identify possible sources of error.
Introduction/Background
Today’s penny is quite different from the penny of two decades ago. Before 1982, pennies were made of an
alloy of copper. Since then, they have been making with an outside coating of copper and an inner core of a
different metal. These differences in the composition of older and more recently minted pennies have resulted
in differences in the penny’s characteristics, including the density (mass per unit volume—volume’s units will
differ depending if it’s a solid or liquid). In this experiment, you will determine and compare the densities of
pennies minted before 1982 and after 1983 and use the density data to try to identify the metal used in the
core of pennies minted after 1983.
Objectives
1. Determine the densities of pennies minted before 1982 and after 1983.
2. Compare the densities of pennies minted before 1982 and after 1983.
3. Identify the metal in the core of the pennies minted after 1983.
Pre-Lab Questions
1. What is the formula for finding density?
2. 1 g/mL is equal to 1 g/cm3. Explain what the difference between these two measurements is.
3. Graph the data from the data table below (in a best-fit line graph). Be sure to properly label both axis
and give the graph a title.
Volume
(mL)
1
2
3
4
Mass (g)
a)
Calculate the slope of the
line (SHOW WORK):
10
25
35
45
4. If a substance has a mass of 141.48 g and a volume of 18 cm3, calculate the substance’s density,
showing work.
5. Use the properties of transition metals table on the next page of this lab (after procedure section) to
determine what the substance in #4 is. ____________________________________
General Chemistry
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General Chemistry
Name:___________________________
Penny Density Lab
Date:____________________Hour:______
Materials
 25 pre-1982 pennies
 25 post-1983 pennies
 Balance
 50-mL graduated cylinder
 Paper towels
Procedure
1. Work with one set of pennies at a time, either pre-1982 or post-1983. Find the mass of 5 pennies from
one set. Record the mass in the appropriate table.
2. Add 5 more pennies to the first group and then obtain the mass of these 10 pennies. Record the mass.
3. Repeat step 2, each time adding 5 more pennies to those already on the balance, until you have
reached 25 pennies.
4. Fill the 50-mL graduated cylinder to the 20-mL mark with water. Be sure to use the bottom of the
meniscus to measure the water level.
5. Still working with the same set of 25 pennies, gently drop 5 of the pennies into the graduated cylinder.
Record the new water level in the appropriate table.
6. Add 5 more pennies to the graduated cylinder, making a total of 10 pennies. Record the water level in
the appropriate table.
7. Add 5 more pennies to the cylinder and record the water level.
8. Repeat step 7 until all 25 pennies are in the cylinder.
9. Discard the water, dry the pennies with a paper towel and return them to the appropriate location.
10. Repeat steps 1-9 using the 25 pennies in the other set of coins.
Informational Table to help complete pre-lab and conclusion questions:
PROPERTIES OF CERTAIN TRANSITION METALS
Melting Point (⁰C)
Boiling Point (⁰C)
Density (g/cm3)
Ionization Energy (kJ/mol)
Atomic Radius (pm)
Common Oxidation Numbers
General Chemistry
Cr
1857 ±20
2672
7.20
653
128
+2, +3, +6
Fe
1535
2750
7.86
762
126
+2, +3
Co
1495
2870
8.9
760
126
+2, +3
Ni
1455
2732
8.92
7.7
124
+2
Cu
1083
2567
8.96
746
128
+1, +2
Zn
420
907
7.14
906
134
+2
Ag
962
2212
10.5
731
144
+1
Au
1064
2808±2
19.3
890
144
+1, +3
Hg
-38.8
356.6
13.5
1007
151
+1, +2
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General Chemistry
Name:___________________________
Penny Density Lab
Date:____________________Hour:______
DATA TABLES:
Data Table 1.1 (Pre-1982 Pennies)
Initial Volume __________mL
Net Volume = Total Volume – Initial Volume.
# of Pennies
Mass (g)
Total Volume
(mL)
Net Volume
(mL)
5
10
15
20
25
Data Table 1.2 (Post-1983 Pennies)
Initial Volume __________mL
Net Volume = Total Volume – Initial Volume.
# of Pennies
Mass (g)
Total Volume
(mL)
Net Volume
(mL)
5
10
15
20
25
General Chemistry
Page 3
General Chemistry
Name:___________________________
Penny Density Lab
Date:____________________Hour:______
Analysis
1. Construct a line graph of your results. Let the Y-AXIS reflect the mass of the pennies. Let the X-AXIS reflect the
volume of the pennies. Plot the data for the pre-1982 pennies first. Then draw the best-fitting straight line (the
straight line that connects as many points as possible). On the same graph, plot the data for the post-1983
pennies. Draw a best-fitting straight line. Label or color-code the line. Graph paper is on the back of this page.
2. How do the graphs compare? Describe the similarities and differences.
3. Find the slope of each line. Show your work.
Slope: Pre-1982 pennies:
Hint: Slope =
𝑌2−𝑌1
𝑋2−𝑋1
Slope: Post-1983 pennies:
Conclusions
1. Why do pre-1982 and post-1983 pennies have different densities?
2.
What do the values you obtained for the slopes of the best-fitting lines represent? (Look back to where you
calculated slope and what the axes represent.)
3.
Find the density of copper on the properties of metals table in this lab. Compare the density of copper with
your value of the slope of the best-fitting line for the pre-1982 pennies.
Density of copper:_____________________
Your slope for pre-1982 pennies:____________________
Compare the two values and explain if they are similar or different and why you think that is:
4. What is the density of the post-1983 pennies? Compare the slope of the line for these pennies with the density
listed for each element on the properties of metals table in this lab. Which elements have a similar density to
your results? (List the 5 closest to your value)
Post 1983 pennies’ density:________________________
Five elements with similar densities:
CONTINUED ON BACK!!!!
General Chemistry
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General Chemistry
Name:___________________________
Penny Density Lab
Date:____________________Hour:______
5. Which metal do you believe to be inside the copper-clad pennies minted after 1983? Explain your answer
BASED ON YOUR EVIDENCE.
General Chemistry
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