Chemistry lab:
Measuring Densities of Pennies
pennies to those already on the balance, until
you have used all 50 pennies. Be sure to
record all data.
4. Fill the graduated cylinder to exactly 20
mL with water. Make sure you read the
water level at the bottom of the meniscus at
eye level. (these 20 mL have to be
subtracted from all your following data)
5. Still working with the same set of 50
pennies, hold your graduated cylinder on an
angle to avoid splashing, gently drop 5 of
the pennies (one at a time) into the
graduated cylinder. Record the new water
level to the tenth of mL (xx.x mL, one
decimal) in the first column of your table.
Find the actual volume of the 5 pennies by
subtracting the initial volume (20.0 mL)
from the total volume.
6. Add 5 more pennies to the graduated
cylinder, making a total of 10 pennies.
Record the new level. Find the net volume
of 10 pennies, by subtracting 20.0 mL.
7. Repeat step 6 for 15, 20, 25, 30. 35, 40,
45 and 50 pennies. Record the water level
each time and subtract 20.0 mL for net
volume.
8. Discard the water. Dry the pennies with
a paper towel thoroughly and return to the
cup.
9. Repeat steps 1-8 using 50 pennies of the
other set of coins. And record your data in
the correct data table on the right. Make
sure the pennies are dry when you measure
the mass. Again, please dry the pennies
with paper towels before returning.
Introduction
Today’s penny is quite different from the
penny of two decades ago. Before 1982,
pennies were made of an alloy (solid
mixture with at least one component being a
metal) of copper. Since then, they have been
made with an outside coating of copper and
an inner core of a different metal. These
differences in composition of older and
more recently minted pennies have resulted
in differences in the pennies properties. One
of these differences is the density, which is
the mass per unit volume (usually in g/mL
or g/cm3). We are going to use the
property density to identify the metal
inside the pennies.
slope n. 4. Mathematics. a. The rate at which
an ordinate of a point of a line on a coordinate
plane changes with respect to a change in the
abscissa. b. Rise over run
density n., pl. densities. b. The mass
per unit volume of a substance under
specified conditions of pressure and
temperature.
Materials
50 pre-1982 pennies
50 post-1983 pennies
balance, 50 mL graduated cylinder
paper towels to dry pennies when done.
Procedures
Important:
Work with one set of pennies at a time,
either pre-1982 (older) pennies or post1983 (newer) pennies !!!!!!!!! (Do not mix)
Figure 1
Density of Pennies
mass/g
1. Find the mass of 5 dry pennies from one
set. (They must be dry!). Record the mass
in the data table of your lab journal.
2. Add 5 more pennies to the first group
and obtain the mass of these 10 pennies.
Record the mass.
3. Repeat step 2, each time adding 5 more
9
8
7
6
5
4
3
2
1
0
0
1
2
Volume / mL
4
Date [_________]
Chemistry lab: Measuring Densities of Pennies
Purpose: Determine the density and use it to identify the metal inside the pennies.
Pre-Lab Questions:
1. Define Density (in words).[…]
2. Write the formula of density (include units). […]
3. What are you measuring today in order to determine density? These are your two variables
will you be graphing. […]
4.. Define alloy. […]
Table 1 Pre- 1982 (older )Pennies
Number
Total Volume
of Pennies in Cylinder
Net Volume of Pennies
(mL) (subtract 20)
Mass (g) of Pennies
5
10
15
20
25
30
35
40
45
50
X axis
→
you will
need the
last two
columns
for the
graph
!!!!
Y axis
Table 2 Post- 1983 (newer)Pennies
Number
Total Volume
of Pennies in Cylinder
Net Volume of Pennies
(mL) (subtract 20)
Mass (g) of Pennies
5
10
15
20
25
30
35
40
45
50
→
X axis
Y axis
Analysis:
1. Using MS Excel, construct a graph of your results for the pre-1982 pennies and post-1983
pennies on the same graph, as shown in Figure 1. Each student has to attach (use scotch tape his
or her own graph (with name) to the report. Let the y axis reflect the mass of the pennies and
the x-axis the volume of the pennies in cm3 (remember mL = cm3). Make sure to label your axes
with (mass/g and volume/cm3). For detailed instructions see separate sheet.
2
Analysis: (continued)
2. Determine the slope of both lines of your graph. Use the equation given by Excel (ax+b), with
a being the slope.
The slope of your graph for pre-1982 (older) pennies is: __________________________
The slope of your graph for post-1983 (newer) pennies is:________________________
The slope will be equal to the density!!!!!
Conclusions
1. What does the slope of each line represent with regards to the pennies (a physical property)?
The slope of each line represents the …..
2. The density for pure copper is 8.92 g/cm3. Compare the density of copper with the value for the
slope of the line for the pre-1982 (older) pennies. Is the slope of this line the same value as the
density of copper? Explain why there are any differences that exist. (experimental
problems……alloys,) .[…]
3. What is your value for the density of the pennies minted since 1983 (newer, post-83 pennies)
(see analysis #2)?
The density of the newer pennies is …..
4. Compare your density value for post-83 pennies with density data for different elements below.
What metal is most likely inside your post-83 pennies (most similar density)? […]
Element
Magnesium
Beryllium
Carbon
Boron
Aluminum
Zinc
Iron
Silver
Lead
Mercury
Tungsten
Gold
Platinum
Density (g/cm3)
1.738
1.848
2.266
2.46
2.699
7.14
7.874
10.49
11.34
13.534
19.3
19.32
21.41
5. Archimedes, a Greek mathematician and inventor of the second century B.C., was commissioned
by the king of Syracuse to find out whether a crown that had been made for the king was fashioned
from pure gold or from a mixture of gold and silver, a less expensive metal. Archimedes could not
use chemical tests, for they would damage the crown, yet he was able to find the answer to the
king’s question. How did he carry out the king’s request?
[…]
3
How to use Microsoft Excel
 to generate the…
Density Graph of Pennies
Open a new Excel file and save it as “penny density” or similar recognizable name.
Make a data table similar to the example below for your two sets of data. You need one column
for volume and two columns for mass. The units (mL and g) have to be in the header with the
words volume and mass and not in the cells with the numbers! Otherwise, Excel does not
recognize your data as numbers later.
If you like “pre-82 pennies” like here written in two lines: choose from *home format (on the
right), *format cell (way down), *alignment and check “wrap text.
Each set of data should also contain 0 mL – 0 g
Here is a sample column with data,
(because no pennies = no mass = no volume). You can
for you to see the format. However,
simply put in first the data of your first set of data and
the values are not correct! Do not
underneath those of your second set. Just make sure the
copy these exact numbers! Use your
corresponding volume and mass values actually belong
own data!!!
together in each row. Save!
Volume/mL
mass/g
Pre-82
pennies
Create a Graph:
mass/g
Post-83
pennies
0
(example graph on the back)
Highlight all three new columns of your new data
table
( without volume/mL and mass/g).
0
0
Click “insert” “scatter” and choose the first option
9.2
18.11
just dots without lines.
17.5
36.05
You can make the graph box bigger by clicking the
26.7
55.01
corner and dragging (the usual way ☺)
37.5
71.15
To add title and axis labels click somewhere inside
10.2
15.21
your graph box. On the way, way top toolbar (above
from where you would usually look, above design) it
19.5
31.09
now reads “Chart Tools”
31.3
44.55
Click “Design” and choose the first chart layout.
40.5
61.88
Title etc. should now appear on your chart and you can
change all text bars. I recommend for chart Title “ Density graph of Pennies”, for Value (x) axis
“Volume/mL” and Value (y) axis “Mass/g”. Right-click to change font, size etc. Save!
Add Linear Trent Line:
• Put your cursor on one data point of your first set of data, right-click and select “add trend line”.
Select the following three in the same window: “Linear”, “Set intercept = 0.0” and “Display
equation on chart”. Click ok. Repeat this for the second set of data. (slope = density)
Beautify and Print
•
•
•
Click somewhere outside the graph before you try to print. (If graph is selected you will only
print the graph without the table … and we want both) Check print preview before you print
From print preview you can access “Page setup” and select “Landscape”, and “fit to one page;
click ok.
You may also beautify the graph and the datasheet to your liking before printing, add your
Name, Period and Date anywhere on your data sheet. Again: Check print preview before you
print !!!!! (Excel does funny things sometimes…) Save again.
Staple, glue or tape the graph into your composition book
4
Volume/mL
mass/g
Pre-82
pennies
0
9.2
17.5
26.7
37.5
10.2
19.5
31.3
40.5
0
18.11
36.05
55.01
71.15
mass/g
Post-83
pennies
0
Zero pennies, zero mass, zero volume for both data sets
First data set for older pennies
(use net volume and mass)
15.21
31.09
44.55
61.88
Second data set for newer pennies right underneath
(again, use net volume and mass)
5