Title: Density of Liquids
Purpose: Find the density of tap water and how a property such as density be used to identify an
unknown substance.
Materials and Apparatus: chemical splash goggles; laboratory apron; laboratory balance;
graduated cylinder (10-mL); 6 plastic micropipets; unknown liquid; tap water
Drawings:
Procedures and Observations:
Procedures: First, put on the safety goggles and lab apron. After that, obtain the micropipets and
label them1-6. Then place micropipette #1 on the lab balance and measure the mass to the
nearest 0.01g. Record the data in Data Table 1. Fill #1 with tap water and measure its mass to
the nearest 0.01g and record in Data Table 1. Then transfer the tap water from the micropipet
into a graduated cylinder. After that, measure and record the volume to the nearest 0.1mL. Then
repeat the above steps with micropipets #2 and #3 so that three sets of mass and volume are
recorded in Data Table 1. After that, Obtain 50mL of an unknown liquid supplied from your
instructor. Using micropipets #4, #5, and #6 repeat the above procedures and record the
measurements in Data Table 2. Carefully dispose of all chemicals as instructed, clean up the
work area, and wash your hands.
Observations: The observations were that the measures for the unknown and the tap water were
very similar in measurements.
Data:
Data Table 1
Trail 1
Trial 2
Trial 3
Mass of empty micropipette (g)
1.02
.98
.96
Mass of filled micropipette (g)
3.39
3.82
3.76
Mass of water (g)
2.37
2.84
2.80
Volume of water (mL)
2.2
2.6
2.5
Density of water (g/mL)
1.08
1.09
1.12
Unknown 1
Unknown 2
Unknown 3
Mass of empty micropipette (g)
.98
.93
.95
Mass of filled micropipette (g)
3.90
3.61
3.40
Mass of unknown (g)
2.92
2.68
2.45
Volume of unknown (mL)
2.6
2.5
2.2
Density of unknown (g/mL)
1.12
1.07
1.11
Data Table 2
Conclusions: The results of Data Table 1 were very similar to the results of Data Table 2. It was
concluded that the unknown was also tap water.
Error Sources: There were no error sources.
Questions:
1. Based on your data, which of the liquids in the table on the next page could be your
unknown? Explain.
TABLE 3 Densities of Some Liquids
Liquid
Density (g/mL)
Ethanol
0.789
Isopropyl alcohol
0.786
Methanol
0.791
Corn oil
0.921-0.928
Water
0.998
Ethylene glycol
1.114
Glycerine
1.261
Based on the data in Table 3 the liquids that could be the unknown could be Water,
Ethylene Glycol, or Glycerine because the density is very close to the average density of
our unknown.
2. Could your unknown be a liquid that is not listed in the table in Question 1? Explain.
The unknown could be a liquid that is not listed in the table in Question 1 because there
are many other liquids in the world and the unknown could have a very different density
than the liquids in the table.
3. Using the formula below, calculate the percent error for the average density of water that
is determined in the investigation. Do the same for the average density of the unknown
liquid. Your teacher will provide you with the accepted value for the density of each
liquid.
Percent error = (measured value – accepted value) divided by accepted value X 100
Percent error for density of water:
10%
Percent error for density of unknown: 10%
4. Why do you think your measured values differ from the accepted density values for water
and the unknown liquid?
I think the results differed because the mass of the micropipets, water, and the unknown
differed from the beginning which would differ the final result even more.
5. What changes could you make in the procedure to increase the accuracy of your results?
The only change I would make is to use a different graduated cylinder every time the
volume was measured because drops of water from the previous measurement could alter
the results.
6. Look again at Table 3. If your unknown had a density of 0.79g/mL and you knew that it
was one of the three substances listed in the table having a density close to your value,
how would you go about determining which liquid was your unknown?
An experiment could be conducted using those three liquids to find out what properties
they have and then perform the same tests to the unknown liquid and the ones that the
properties match are the same liquids.
7. Ice floats on water. Is ice more or less dense than water? How do you think the density of
ice affects the survival of water-dwelling organisms in environments where temperatures
fall below the freezing point?
Ice is less dense than liquid water. I think it doesn’t really affect water-dwelling
organisms because the water only freezes into ice on the top of the body of water and the
liquid water stays flowing as usual.
8. When stating the density of a liquid, why is it necessary to state the temperature?
It is necessary to state the temperature because there are different forms of many liquids
that occur in different temperatures which changes the density.
9. The density of petroleum oil is less than the density of sea water. How would this
property affect methods used to clean up an oil spill in the ocean?
It would affect the methods to clean up the spill because since it is less dense then it
won’t float and it will sink and spread throughout the ocean which makes it much more
difficult to clean up.
10. Describe the procedures you would use to measure the densities of a solid and a gas.
Explain how these procedures would differ from those used to determine the density of a
liquid.
To measure the density of a solid would be to get the mass by weighing it and then get
the volume by putting it in a graduated cylinder with water and subtracting the volume of
water. After that just divide. For the gas, put the gas into a container that the volume is
known and then weigh the gas in that container and then just divide.