Mass, Volume, and Density
Purpose: The purpose of this lab is to determine the densities of unknown materials and to
use measured density values to identify unknown compounds.
Background: An old riddle asks “Which is heavier, a pound of feathers or a pound of lead?”
The question is nonsensical, of course, since a pound of feathers and a pound of lead both
weigh the same, one pound. Nevertheless, there is clearly something 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 the understanding of the relationship that exists between a substance’s mass and
the volume it occupies. The relationship is expressed by the physical property called density.
Density is defined as the ratio of the substance’s mass to the volume it occupies.
Density 
Mass of the the substance (g)
Volume of the substance (mL)
In this experiment, you will measure the mass and volume of several unknown materials. You
will then use your data to explore the relationship between mass and volume of the materials
and to calculate their density.
Materials:
Digital scale
ruler and caliper
25-mL, 100-mL and 250-mL graduated cylinders
Various square, rectangular, cylindrical and spherical samples
Procedure:
1. Measure the mass of several separate samples of the same material to the nearest 0.01
gram, using a digital scale. Be certain that the scale has been zeroed (“tare”) before each
measurement. Repeat this for all the pieces of the other remaining materials. Record the
data with the proper number of significant figures. You should have a minimum of nine
measurements.
2. Find the corresponding volume for each of the samples. Determine the volume by two
separate methods, first by direct measurement using the measuring tools provided, and
second by water displacement. Water displacement is accomplished by measuring the
change in water volume in a graduated cylinder after the sample is completely submerged
in the water. Record measurements to the appropriate decimal place for each method.
CAUTION:
DO NOT DROP THE SAMPLE IN THE GLASS CYLINDER AS IT WILL
BREAK OUT THE BOTTOM OF THE CYLINDER.
3. Calculate the density for each measurement, using volumes determined by both direct
measurement and water displacement. Round calculated values to the hundredth place.
4. Graph the volume versus mass for each of the different materials. Draw a line which best
represents the model of the density (“best-fit” line). Calculate the equation of this line
(y = mx + b) and determine the density from the slope of the curve. Identify in your data
table which measurements were used to calculate Volume 1. (4 graphs per page)
5. Calculate the percent error for the calculated density of each object relative to the density
predicted by the slope of a chosen graph. Record these values in the last column of your data
table. Identify whether it is “Density 1 % Error” or “Density 2 % Error” in your data table.
% error = l predicted density - calculated density l x 100%
predicted density
6. There will be a list of materials on the board with associated actual densities to determine the
identity of your unknown materials. Once you have identified your unknowns, calculate the
percent error for the predicted density of each material relative to its actual density value.
Indicate which predicted density you choose for each material by highlighting the equation on
the chosen graph. Show all four % error calculations under the data table in your lab report.
% error = l actual density - predicted density l x 100%
actual density
Sample Data Table:
Material/S
hape
Dimensions
(ruler)
Dimensions
(caliper)
Volume 1
(calculated)
Volume 2
(water
displacement)
Mass (g)
Density 1
(g/mL)
Density 2
(g/mL)
material A
(cylinder)
material A
(small cube)
material A
(large cube)
material B
(small cube)
etc
Post Lab Questions:
1. Which volume measurement method (calculated or water displacement) gave the best result
for density and why? Use your data (% errors) to support your answer.
2. In the equation of the line calculated from your graph, the slope “m” is the density. What
does the “b” represent in the equation? (hint: look at the units)
3. What does the “percent error” for the calculated density of each object compared to predicted
density tell you about your data? What does the percent error for predicted density compared to
actual density tell you? How might you account for any differences?
4. Looking at your density values, what does this experiment demonstrate about the density of a
metal? What does it demonstrate about the densities of different materials?
%
error