GT Chemistry
Name: _____________________________________________________ MOD: _________
Laboratory Guide Packet
Unit: Skills
This packet includes all of the labs for this unit. Once a lab has been completed you will turn in the whole
lab packet to be graded and returned. This does not take the place of your laboratory notebook. All
worksheets are only to be used to turn in work, all calculations should be done in your lab notebook.
(Please note the only time this lab packet will not be turned in is when there are lab assignments given backto-back).
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GT Chemistry
Table of Contents
Title:
Pages
Size of an Oleic Acid Molecule ……………………………………………………………………………………..
3-7
Determining the Thickness of Aluminum Foil …………………………………………………………………
7-11
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GT Chemistry
SIZE OF AN OLEIC ACID MOLECULE LAB
Molecules are so small that you often need to use scientific notation to express their size. These molecules
often cannot be seen in a microscope nor be measured directly even with the most sophisticated scientific
equipment. In these cases, the size of a molecule needs to be determined by indirect calculations.
In this experiment, you will calculate the length of a molecule of oleic acid. This is a type of organic
compound called a fatty acid with the formula C17H33COOH. When a drop of oleic acid is placed in water,
it spreads out over the surface in a thin film. If there is sufficient room, the layer spreads until it is only one
molecule thick. The –COOH part of the molecule mixes with water. The remainder of the molecule does
not mix with the water but sits on top as shown in Figure 1. By measuring the thickness of the film, you will
have an estimate of the length of the oleic acid molecule.
OBJECTIVES
When you have completed this activity, you should be able to:
1. Calculate the length of a molecule of oleic acid.
2. Express numbers in scientific notation.
in order to manipulate values in algebraic equations and judge whether a solution is reasonable.
MATERIALS
large shallow tray, lycopodium powder, capillary pipet, 0.5% oleic acid-ethanol solution, meter stick ,
ethanol (C2H5OH), graduated cylinder, 10 ml
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PRE-LAB INFROMATION
A beaker (Figure 1) is filled with marbles to the 2.00 x 102 mL mark.
2.00 x 102 mL
Figure 1
Assuming that the space between marbles (molecules) is negligible, what is the
volume occupied by the marbles? By definition, 1.0 mL = 1.0 cm3, therefore, 2.00x102 mL = 2.00x102
cm3
When these marbles are spread out to one marble thickness, they cover a rectangular cake pan with
the dimensions shown in Figure 2.
Figure 2
Calculate the area occupied by the single layer of marbles in Figure 2. 1.21x101 cm x 1.10x101 cm = 1.33x102
cm2.
Using the volume from Figure 1 and the area from Figure 2, calculate the height of the marble layer, h.
(Figure 3) Show all your work. Include units. Volume = length x height x width, Area = length x width,
therefore: Length (height) = volume/area
height = 2.00x102 cm3/1.33x102 cm2 = 1.50 cm
Figure 3
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If 40 drops of liquid have a volume of 1.0 mL, what is the volume of one drop? 1 drop (1.0 ml/40 drops) =
2.5x10-2 mL/drop
How many mL of oleic acid are in 1.0 mL of oleic acid solution? See Procedure 4 for the concentration of
the oleic acid solutions. mL x 0.005 = 0.005 mL oleic acid
PROCEDURE
1.
2.
3.
4.
Add water to a depth of about 1 cm in a clean tray. Make certain that the tray is level.
Cover the entire surface of the water with a very thin layer of lycopodium powder.
Add one drop of ethanol to the tray. Record your observations in Data Table 1.
Hold a pipet vertically over the center of the tray and close to the surface. Carefully add one drop
of the 0.5% oleic acid-ethanol solution to the surface of the water. Record your observations in Data
Table 1. Allow the surface to stabilize. Treat the resulting area of oleic acid as a circle.
5. Measure the diameter of the film at five different places and record in Data Table 2.
6. Determine the volume of one drop of solution by counting the number of drops of the oleic acidethanol solution needed to fill the 10 mL graduated cylinder to the 1.0 mL mark. Check by
counting the additional number of drops to raise the volume to the 2.0 mL mark. Record this
number in Data Table 1.
7. Clean the tray by washing it with hot, soapy water and rinse several times with clean water. Repeat
Procedures 1, 2, 4, and 5 for a second trial.
Student Sheet: SIZE OF AN OLEIC ACID MOLECULE LAB
DATA
DATA TABLE 1
Procedure
Number
Observation
3
4
6
DATA TABLE 2
Diameter Oleic Acid Film (cm)
Trial
1
2
3
4
5
#1
#2
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RESULTS
Trial 1
Trial 2
Average diameter of film
cm
cm
Area of film (Area = d2/4)
cm2
cm2
Volume of 1 drop of solution (1mL/# drops)
mL
mL
mL
mL
cm
cm
Volume of oleic acid in 1 drop
(concentration of oleic acid/volume of 1 drop)
Length of oleic acid molecule
(Volume = Area x Thickness)
ANALYSIS AND CONCLUSIONS
1. Compare the observations in Procedures 3 and 4. Explain the significance of the observed
differences.
2. Convert your answer for the length of the oleic acid molecule from centimeters (cm) to nanometers
(nm). (1 cm = 107 nm) Express your answer in scientific notation.
___________________________
3. Why is the nanometer unit a more convenient unit to use than the centimeter?
4. Calculate percent error using 2.7 nm as the accepted value for the length of the oleic acid molecule.
% error = |measured value – accepted value| x 100 = ________________
accepted value
5. Avogadro’s number can be estimated from knowing the molecular mass of 1 mole of oleic acid
molecules. Since we know the concentration of oleic acid, the volume of it used, we can estimate
the number by using the formula below:
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 A

V 
3
N = 282 
Calculate Avogadro’s number using your obtained data. _____________________
EXTENSION
A huge oil spill has occurred in a body of water. The amount of oil spilled is undetermined, but we can
measure the thickness of the oil and the area that the oil spill occupies. From this we should be able to
determine the volume of oil that was involved in the spill. Use the following information to calculate the
volume of oil that was spilled in the accident. Show your work.
The average thickness of the oil spill as measured in several spots is 2 x 10-3 cm
The area that the oil spill has covered is 2.05 x 1013 cm2
DETERMINING THE THICKNESS OF ALUMINUM FOIL
PRELAB
1. The formulas that will enable you to find the thickness of the foil can be derived by rearranging and
substituting into the formula for the volume of a rectangular solid. The volume of a regular solid is
found by using the formula:
V=LxWxH
where L = length; W = width; and H = height. Substitute T (thickness) for H. Rearrange the formula so
that it solves for T and write it below.
2. The length of a rectangle multiplied by its width (L x W) can also be written as what? What scientific
instrument would you use to measure this?
3. If you know that the density of aluminum is 2.70 g/cm3 what would you need to measure about the
aluminum to find its volume? What scientific instrument would you use to measure this?
INTRODUCTION
Everyone is familiar with aluminum foil. Reynolds™ Wrap comes in three different weights: Standard
aluminum foil, Heavy Duty aluminum foil, and Extra Heavy Duty aluminum foil. What differentiates the
three types of foil is the thickness of the foil. If one wanted to quantify the differences between the three
types of foil, one could attempt to measure its thickness. Because laboratory tools normally available will
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not be suitable for the direct measurement of the thickness of a piece of aluminum foil, you will have to
develop a method to indirectly measure its thickness.
Problem solving often involves the use of one set of measurements and known properties (such as density)
to indirectly measure other quantities. In this activity, you will use a ruler and a balance to collect data then
mathematically determine thickness.
The formulas that will enable you to find the thickness of the foil can be derived by rearranging and
substituting into the formula for the volume of a rectangular solid. The volume of a regular solid is found by
using the formula:
V=LxWxH
where L = length; W = width; and H = height. Substitute T (thickness) for H.
DETERMINING THE THICKNESS OF ALUMINUM FOIL LAB REPORT
For this lab investigation you will be creating a formal lab report. Complete the following on your own
notebook paper or in your lab notebook.
INTRODUCTION: State the purpose of the experiment, followed by a brief summary of the background
information on which the experiment is based.
PROCEDURE: Write up the procedures for your proposed experiment. Submit the completed
procedures to your teacher for approval before starting the experiment.
The procedures are a narrative that explains the steps that were performed to test the hypothesis under
controlled conditions. The procedures should include the following elements:









Write in paragraph form and in the past tense.
Include materials in the narrative.
Use the proper names of equipment used in the experiment.
Write a separate paragraph for each major step of the procedure.
Use titles for each section of the procedure.
Identify the independent variable, dependent variable, control, constants and if trials were repeated.
An appropriate experimental design
Units of measurement
Proposed calculations
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STUDENT SHEET: DETERMINING THE THICKNESS OF ALUMINUM FOIL LAB REPORT
INTRODCUTION:
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PROCEDURE:
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DATA AND CALCULATIONS:
1. Construct a data table that will be used to collect your data. Be sure to include units.
2. Construct a table that will show the calculations used to determine the thickness of each piece of
aluminum foil. Be sure to give the formula and units for each calculation in the headings.
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SUMMARY OF RESULTS
1. Construct a Table to show the calculated average thickness of each aluminum foil.
CONCLUSION: Give a short summary of your findings in the experiment
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POST LAB QUESTIONS: Answer these questions.
1. How can you validate the accuracy of your measurement?
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2. Perform an error analysis using the average of accumulated class data as the theoretical thickness.
Comment on the accuracy of your results.
Accuracy: ______________________________________________________________
3. How precise are your answers? Explain. __________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
4. If you had used a very crude balance that allowed only one significant figure, how would this have
affected your results for: (Be specific)
a. Area? __________________________________________________________________
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b. Volume? _______________________________________________________________
c. Thickness? _____________________________________________________________
EXTENSION QUESTIONS:
1. Could this method be used to determine the thickness of an oil spill? What information would be
needed?
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2. A very thin layer of gold plating was placed on a metal tray that measured 25.22 cm by 13.22 cm. The
gold plating increased the mass of the plate by 0.0512 g. Calculate the thickness of the plating. The
density of gold is 19.32 g/cm3. _____________________________________
3. How could you apply this method to determine the length of a molecule?
[Hint: Let T = length of the molecule]
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