Lab #1: Determination of Mass, Volume and Density
Introduction
In order to achieve reasonable results in experimentation, proficiency in the use of the SI
(metric) system and with the measuring instruments commonly found in the laboratory is
essential. In this laboratory exercise the density of a solid, a pure liquid and several
solutions will be determined. Accurate results will indicate proper use of the instruments
utilized in this laboratory exercise.
Theory
In chemistry lab measurements, the SI unit of mass is the gram (g), and the unit of volume
is the milliliter (mL). For the volume of the solids, the unit (cm3) is commonly used
interchangeably with mL. In this experiment all volumes will be expressed in mL.
Density, like color, odor, solubility, melting point, and boiling point is a physical property of
a substance. Therefore, density may be used in identifying a substance. The density of a
substance is defined as mass per unit of volume. The density of a solid or the density of a
liquid are both expressed as grams per milliliter (g/mL).
Gold (Au) has a much higher density than aluminum (Al). This means that a gold cube has
greater mass than an aluminum cube of the same size. Review the information provided in
the table below for equal volumes of aluminum and gold.
Measured Quantity
Volume
Mass
Density
Aluminum
1.00 mL
2.70 g
2.70 g/mL
Gold
1.00 mL
19.7 g
19.7 g/mL
The density of a solution composed of two substances is not the same as the density of
either substance in the solution. The density of solutions vary with the concentration of the
solution (a value that indicates the quantity of solute dissolved into the solvent). In this
case sodium chloride, NaCl, is the solute and water, H2O, is the solvent.
The concentration of a solution can be described in terms of the solution’s percentage
composition on a weight basis. For example, a 5.00% NaCl solution contains 5.00 g of NaCl
(solute) for every 100 g of solution.
Purpose
1. To determine the density of a solid and of several solutions of varying concentration.
2. To determine the concentration of an unknown solution using a graph of densities.
Procedure
Part A: The Density of a Solid
1. Obtain a solid of unknown density and record its identifying number. Determine and
record the mass of the solid to the nearest 0.01 g.
2. Determine the volume of the solid using the displacement method. Put about 70 mL
of water into the 100 mL graduated cylinder. In order to do this accurately you must
read the bottom of the meniscus in the graduated cylinder at eye level. Read and
record the volume of the distilled water to the nearest 0.1 mL.
50
Read here!
44 correct
45 incorrect
40
3. Tilt the graduated cylinder and carefully slide the unknown solid into the cylinder.
4. Again read and record the volume of the water in the graduated cylinder to the
nearest 0.1 mL. The difference in the volume readings (volume of the water
displaced by the solid) is equal to the volume of the solid.
Part B: The Density of a Liquid
1. Determine the mass of a clean, dry 10 mL graduated cylinder to the nearest 0.01 g.
2. Fill the 10 mL graduated cylinder to approximately the 7 mL mark with distilled
water. Determine and record the volume of the distilled water to the nearest 0.01
mL.
3. Determine the combined mass of the cylinder and the water to the nearest 0.01 g.
4. Calculate the density of the water and record this as the density of a 0% solution.
5. Rinse the same 10 mL graduated cylinder with a small amount of 5.00% NaCl (aq).
Then fill the graduated cylinder to approximately the 7 mL mark with 5.00% NaCl
(aq). Accurately determine the volume of the solution to the nearest 0.01 mL.
6. Determine and record the mass of the cylinder and solution to the nearest 0.01 g.
From these data you can determine the net mass of the solution. Use the same
balance for all mass determinations in Part B.
7. Rinse the graduated cylinder out with a small amount of distilled water. Repeat steps
5 and 6 for the 10.0%, 15.0%, 20.0% and unknown solutions, rinsing out the
graduated cylinder with distilled water and the solution about to be massed after
each trial. Determine the net mass for each solution. If there are drops of solution
above the level of the solution being massed, the cylinder must be emptied, rinsed
and dried.
Data and Calculations
Part A
1. Calculate the density of the unknown solid from the determination of mass and
volume of the solid. You must list the number found on your solid in the data section.
Part B
1. Calculate the density of each of the solutions, from 0% (distilled water) to 20.0%
including the unknown solution from the determinations of the net masses and
volumes.
2. Construct a graph which shows density versus concentration for the distilled water,
5.00%, 10.0%, 15.0% and 20.0% NaCl (aq). (Use 0% as the concentration for the
distilled water.) Draw a straight line that best fits the points as you have plotted
them.
3. Determine the concentration of the unknown NaCl (aq) by plotting the density of the
solution on the appropriate axis. Read this to the best fit line and then read down to
the “x” axis giving the solution concentrations. This should be the concentration of
the unknown NaCl (aq) solution.
Sample Data and Analysis Table
Part A
Solid #
Mass
(g)
Volume
(mL)
Density
(g/mL)
Part B
Solution
0.0 %
(water)
5.00 %
10.0 %
15.0 %
20.0 %
unknown
Mass of
graduate
(g)
Mass of graduate
and NaCl (aq)
(g)
Mass of NaCl
(aq)
(mL)
Volume of
NaCl (aq)
(mL)
Density of
solution
(g/mL)
Conclusion
Summarize the results you have obtained in the laboratory exercise.
i. State the density of the unknown solid and the densities of pure distilled water as
well as each of the NaCl (aq) solutions including the unknown.
ii. Discuss how the graphical method used in this experiment allowed for the
identification of the concentration of the unknown solution.
iii. Discuss probably sources of error in your results.
Conclusion (i.) can be shown in a data and analysis table similar to the one above.
Directions for Graphing
Refer to the handout entitled “The Laboratory Report”