ADAMSON UNIVERSITY
College of Engineering
Chemical Engineering Department
M a ni l a
EXPERIMENT NO. 3
MEASUREMENT OF DENSITY
51080/ F/ 7:00 10:00/OZ404
Submitted by:
Agoto, Ariadna L.
(201312884)
Roderno, Karl Philip G.
(201513016)
Santiago, Dana Michiko M.
(201314338)
Submitted to:
Engr. Robert Delfin
Date of the Experiment: July 21, 2017
Date of Submission: August 04, 2017
ABSTRACT
In this experiment, densities of various liquids were determined using different methods -
by using pcynometer, Westphal balance, and by measuring mass using the weigh by difference
technique and volume. The effect of solute concentration to density was also observed.
INTRODUCTION
Density is an intensive property of matter. It is a measure of the compactness of matter
with within a substance and also defined as the ratio of mass and volume. In density, the
temperature must be recorded because volume changes in different temperatures, so the density
calculation is effected as well. Density of a substance remains the same at constant temperatures;
because of this we can identify different substances on their density. By simply determining the
mass of a known volume of liquid, densities of liquids may be measured.
THEORETICAL BACKGROUND
The mass density or density of a material is defined as its mass per unit volume. The
symbol most often used for density is (the Greek letter rho). In some cases (for instance, in the
United States oil and gas industry), density is also defined as its weight per unit volume;
although, this quantity is more properly called specific weight. Less dense fluids float on more
dense fluids if they do not mix. This concept can be extended, with some care, to less dense
solids floating on more dense fluids. If the average density (including any air below the
waterline) of an object is less than water (1.0 g per mL) it will float in water and if it is more than
water's it will sink in water. In some cases density is expressed as the dimensionless quantities
specific gravity (SG) or relative density (RD), in which case it is expressed in multiples of the
density of some other standard material, usually water or air/gas.
Mathematically, density is defined as mass divided by volume:
=
Where: is the density, m is the mass, and v is the volume
There are different methods that can be used in determining the density of a certain
substance.Some volume measuring devices may be used cylinders and pipettes.
Another device used to measure is the pycnometer. It is a special
glass flask which is used for determining a relative density of liquids. The
bottle has a special glass stopper. The stopper has a hole which allows
liquid to overflow as the stopper is inserted so that it ensures an accurate
full fill every time.Density determination by pycnometer is a very precise
method.
To get the density using a pycnometer, determine the weight of
the unknown liquid inside the sample by weighing the pycnometer with
liquid minus the empty pycnometer. Divide the obtained mass to the
volume of the pycnometer.
Mathematically, it can be explained as:
20
=
20
For specific gravity measurements, Westphal Balance or
Mohrs Balance is used. This is used to measure liquid densities
heavier and lighter than water. A plummet is suspended from the
beam and placed in a cylinder containing the liquid sample. It works
on the principle that the plummet on the balance will be buoyed by
the weight of liquid equal to the volume displaced. Riders are placed
on the beam in succession until the beam balances.
Data Analysis
The experimental value (EV) is of course different from the actual theoretical value (TV).
This is due to the errors present within the experiment. The formula to get the value of the
percent error is expressed by:
% = 100
METHODOLOGY
This experiment aimed to obtain the density of the liquid sample using three different
methods. One is the most often used method, which is by measuring the mass and then dividing
it to its volume, second is by using a Westphal Balance, and third is by using a pycnometer. The
effects of impurity was also measured through adding water to the liquid sample and calculating
the density changes.
Material, Reagents, and Instrumentation
This experiment required distilled water, 30 mL ethyl alcohol, 30 mL ethyl acetate, and
30 mL methyl alcohol. For the materials and instruments used, the experimenters used graduated
cylinders, test tubes, thermometer, analytical balance, Westphal balance.
A. Measurement of Mass and Volume
An empty, dry, and clean graduated cylinder was weighed using an analytical balance. 10
mL of the liquid sample of was added to the graduated cylinder and then weighed once more.
The temperature of the liquid was then measured using a thermometer. The weight of the liquid
sample was calculated by subtracting the mass of the cylinder with the liquid to the empty
cylinder. The density was then calculated. The process was repeated with the other liquid
samples.
B. Measurement of Specific Gravity using Westphal Balance
The balance of the Westphal balance was adjusted by adjusting leg support until the
bubble in the level indicator is at the center. The cylinder was filled with the liquid allowing the
liquid to flow along the side of the container to avoid formation of bubbles. The plummet was
placed on the hook and was immersed in the cylinder with the liquid sample. The arrest knob
was unrested and the rider was placed on the notch of the balance. Then, the rider was moved
just before the pointer swings fully to the right. Adjusting of the chain until to the pointer points
to the middle was done to read the specific gravity. The procedure was done to the other liquid
samples.
C. Measurement of Density using the Pycnometer
An empty, dry, and clean pycnometer was weighed and the gathered data was recorded.
The pycnometer was filled with distilled water until it overflows. It was then covered and the
overflow was wiped to dry the pycnometer. Its temperature was measured and recorded. The
volume of the water was calculated using the density of water at the measured temperature. The
process was the repeated to the other liquid samples.
D. Effect of the Solute Concentration to Density
An amount of methanol solution of different concentrations (10%, 30%, 50%, 70%, 90%)
was prepared. It was filled to the pycnometer and then its density was calculated. A plot of
density vs solute concentration was then made for better presentation. From the plot, the pure
density of methanol was determined.
Results
The results observed during the experiment for the measurement of density using three
different methods for the different liquid samples was tabulated and plotted in order to present
the data in a clear and concise form.
I. Measurement of Mass and Volume
COMPOUND
Methyl Alcohol Ethyl Acetate
T1 T2 T3 T1 T2 T3
Mass of empty
container (grams)
Temperature of
liquid sample (C)
Volume of Liquid
Sample (mL)
Mass of empty
container + liquid
(grams)
Mass of liquid
sample (grams)
Density of liquid
sample (g/mL)
Average Density
Percent Error
II. Measurement of Specific Gravity using Westphal Balance
COMPOUND
Temperature (C)
Specific Gravity
III. Measurement of Density using Pycnometer
MEASUREMENT UNIT
Mass of empty pycnometer grams
Mass of pycnometer + water grams
Temperature of water C
Mass of water grams
Density of water g/mL
Volume of water = volume of pycnometer g/mL
COMPOUND
Methyl
Methanol
Acetate
Mass of pycnometer + liquid (grams)
Temperature of liquid sample (C)
Volume of liquid sample (mL)
Mass of liquid sample (grams)
Density of liquid sample (g/mL)
Percent Error
Average Percent Error
IV. Effect of Solute Concentration to Density of Solutions
Solute Concentration COMPOUND
(%wt) Methanol Methyl Acetate
10%
30%
50%
70%
90%
Discussion
Using three different methods. The density of the liquid samples was measured. The most
often used formula for density () was used, which uses the mass of the liquid over its volume.
The density measurement through the pycnometer produced lower percentages of error
compared to the procedure A. This might be due to the constant volume presented by the
pycnometer. For the procedure A, the average density for methanol at 30.4 C was 0.8994 g/mL,
which has a 15.01% error compared to the true value which is 0.7827 g/mL and the average
density of ethyl acetate was 1.1731 g/mL, which has a
REFERENCES
Argondizo, A. (n.d.). Retrieved from scribd: https://www.scribd.com/document/57033170/Density-
Determination-by-Pycnometer.
Biswas, K. (n.d.). Determination of Density. Retrieved from scribd:
https://www.scribd.com/document/94520680/Determination-of-Density-Lab-1
Density. (n.d.). Retrieved from https://www.saylor.org/site/wp-content/uploads/2011/04/Density.pdf.
Density Determinations and Various Methods to Measure Volume. (n.d.). Retrieved from
General Chemistry: http://www.webassign.net/question_assets/ucscgencheml1/lab
_1/manual.html.
Density Determination by pycnometer. (n.d.). Retrieved from
https://www.fpharm.uniba.sk/fileadmin/faf/Pracoviska-
subory/KFCHL/ENG/lectures/Physics/1.Density-pycnometer.pdf
Westphal Balance. (n.d.). Retrieved from http://physics.kenyon.edu/EarlyApparatus/Fluids/Westphal_
Balance/Westphal_Balance.html
NOMENCLATURE
Greek symbol for rho. Represents the value of the density (Unit: g/mL)
m - Mass
v - Volume
g - Unit of mass in grams
mL - Unit of volume in milliliters
C Unit of temperature in degrees Celsius.
https://www.scribd.com/document/94520680/Determination-of-Density-Lab-1
