Density Laboratory
Theoretical Background (Notes)
PROCEDURE
A. Density of a Liquid
In the first part of this experiment you will determine the density of three different volumes of water.
1. Weigh an empty, dry 50 mL graduated cylinder.
2. Add exactly 10.0 mL of water to the cylinder. Remember, the bottom of the meniscus should just be touching the 10.0
mL line. Hint: Add water up to about the 9mL mark and use a dropper to reach the 10.0 mL mark.
3. Weight the cylinder + 10 mL of water. Calculate the density of the water by determining the mass of water and dividing
it by 10.0 mL (the volume of the sample).
4. Add water up to the 30.0 mL mark and weigh.
5. Add water up to the 50.0 mL mark and weigh.
6. Calculate the densities for the other two volumes.
7. As a beginning exercise in graphing, plot the masses of water on the vertical scale versus the volumes of water on the
horizontal scale.
B. Density of a Solid Object
Use your balance to determine the mass of a metal cylinder to 0.01 g. The volume of the cylinder will be
determined using two different methods. The density (d=m/v) will be calculated and compared for the two volume
measurements.
1. Volume from linear measurements:
Perhaps the simplest method of finding the volume of an object utilizes measurement. For instance, the volume
of a rectangular solid can be found by multiplying its height times its length times its width. The volume of a cylinder can
be found by multiplying π times the square of the radius times the height. (V = πr2h) The radius is ½ the diameter and π
is approximately 3.14. Your unknown solid object is a cylinder. Calculate its volume using the method above that applies
2. Volume from water displacement:
The method above is only useful for regular solids whose volumes are related by a formula to the measurements.
The volume of an irregular solid must be determined by using a different method. One such method utilizes the
displacement of a liquid.
Half fill a graduated cylinder with water. Read the volume of water to 0.1 mL. Slant the cylinder and slowly slide
in the solid object. The object should be totally immersed in the water. Again, read the level of the liquid to the nearest
0.1 mL. The difference in the levels of the liquid equals the volume of the solid object. \
C. Density of a Salt Solution
The density versus percent concentration of several aqueous sodium chloride solutions are provided in the Data
Sheet section. Prepare a graph by plotting the percent by mass of sodium chloride on the x-axis and density on the yaxis.
Weigh a 150-mL beaker to at least 0.01 g and pipet 10.00 mL of your unknown sodium chloride solution into the
beaker. Weigh the beaker and contents and calculate the density of the salt solution. Use the graph to determine the
mass percent of sodium chloride in the salt solution. (Note: The densities presented for the salt solutions were measured
at 20 ºC. Although densities are temperature dependent, the values are accurate to three significant figures after the
decimal between 18 ºC and 24 ºC. If the temperature of the solution is not in this range, there will be slight error.)
Data Collection/Analysis and Results/Questions
A. Density of Water
1. Fill in the following table. (INCLUDE UNITS!)
10 mL
30.0 mL
50.0 mL
__________N/A__________
__________N/A__________
Mass of graduated
cylinder + water
Mass of empty graduated
cylinder
Mass of water
Density of 10.0 mL
sample of water
Density of 30.0 mL
sample of water
Density of 50.0 mL
sample of water
________N/A___________
________N/A____________
__________N/A__________
___________N/A__________
Show calculation setups below:
10.0 mL
30.0 mL
50.0 mL
2. Graph mass (g) on y-axis, volume (mL) on x-axis. Title the graph and label each axis. Calculate the slope and
equation of the line.
3. In this case what does the slope of the line represent?
4. Does the density of water depend on its mass? Explain your answer.
B. Density of a Metal Cylinder
1. Linear measurement method – Collect data (INCLUDE UNITS!)
Number on metal cylinder
Mass of metal cylinder
Height of metal cylinder
Diameter of metal cylinder
Radius of metal cylinder
Volume of metal cylinder
Density of metal cyinder
2. Volume measurement method – Collect data (INCLUDE UNITS!)
Mass of metal cylinder
Initial volume of water in graduated cylinder
Final volume of water in graduated cylinder
Volume of metal cylinder *Calculations
Density of metal cylinder *Calculations
*Show calculations:
3. Suggest reasons for the differences between the two density measurements.
4. Using available density data, predict the composition of your cylinder. Once you have a prediction, calculate the
percent error for the linear measurement method and the percent error for the volume measurement method.
C. Density of a Salt Solution
1. Complete the following table (INCLUDE UNITS FOR ALL MEASUREMENTS!)
Unknown number
Mass of beaker
Mass of beaker + 10.0 mL of unknown
Mass of 10.00 mL of unknown
Density of unknown
2. The densities of several water-sodium chloride mixtures are reported below. Plot the % mass of sodium chloride on
the horizontal (x) axis and the density on the vertical (y) axis.
Density of Salt Solutions (g/mL) vs. Concentration of NaCl (mass percent)
% NaCl
Density (g/mL)
0.00
0.998
5.00
1.034
10.00
1.071
15.00
1.108
20.00
1.148
25.00
1.189
.
3. From the graph, determine the percent by mass of sodium chloride in your unknown.