Density of Pennies Lab
Purpose: The purpose of this lab is to measure volume and mass for pre and post
1983 pennies, graph this data, and determine the two densities by graphing methods.
The identity of the composition of these pennies will be determined.
Materials: 25 pre and 25 post 1983 pennies, 50 ml graduated cylinder, water, balance
Procedure: Do not find the mass of wet pennies. Do the volume last!
1. Find the mass of 5 older pennies on the balance. Add 5 more and find the mass
of 10 pennies. Continue until you have 25 pennies. Record the data below.
2. Add water to the 20.0 ml mark on the graduated cylinder. Add 5 pennies and
read the new volume. Continue with all 25 old pennies. Record volumes below.
3. Place the pennies on a paper towel to dry.
4. Repeat with the 25 new pennies.
# Pennies
(OLD) 5
10
15
20
25
(NEW) 5
10
15
20
25
“y”
Mass (g)
DATA
Initial vol. of
water (no
pennies)
Final vol. of
water
“x”
Vol. of
pennies
Analysis
1. Graph the data. Use one color for the old pennies and one for the new
pennies. Place the mass on the “y” axis and the volume on the “x” axis.
2. Determine the slope of each line. Show this clearly on your graph. Record the
slopes here:
Pre-1983 pennies: ________________ Post-1983 pennies: _________________
3. The slope is describing how mass changes with volume. What physical property
is this?
4. The pre-1983 pennies are solid copper. The density of copper is 8.920 g/ml.
Compare this to the slope of your pre-1985 line. Calculate your percent error:
your value – 8.920
__________________
X 100
8.920
5. The slope of your post-1983 pennies line should give you the identity of the
metal that makes up most of the mass. Compare your value to the attached list
and identify the metal in these pennies. List several if more than one fits the
slope.
6. Why do you think we began making pennies out of a different metal?
7. How could you find the volume of a rock that floats in water?
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