Oleic Acid Teacher’s Guide (Large Tray Option)
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STEM ED/CHM Nanotechnology at UMass Amherst
A Teacher’s Guide for the Oleic Acid Thin Film Activity
The Nanoscale Context: Students apply an understanding of relationships among surface,
area, depth, and volume in order to calculate the nanoscale thickness of a thin film of oleic
acid that forms on the surface of tray of water.
The STEM Context: This activity can be integrated into a study of measurement
systems, miscibility of liquids, and the intermolecular forces
National Science Education Learning Standards Examples
 Science as Inquiry Standard; Grade 5-8 (Page 145): “Use appropriate tools and
techniques to gather, analyze, and interpret data.”
 Physical Science Content Standard B; Grades 9-12 (Page 179): All students should
develop an understanding that “The physical properties of compounds reflect the
nature of the interactions among its molecules……”
Massachusetts Science and Technology/Engineering Learning Standards Examples
 Physical Science; Grades 6-8 (Page 67): “Recognize that the measurement of volume
and mass requires understanding of the sensitivity of measurement tools …..and
knowledge and use of significant digits.”
 Chemistry, High School (page 70): “Identify how hydrogen bonding in water affects
a variety of physical, chemical, and biological phenomena…….”
Massachusetts Mathematics Learning Standard Example
 Measurement; Grades 7-8 (Page 65); “Demonstrate an understanding of the
concepts and apply formulas and procedures for determining measures……”
 Measurement; Grades 9-10 (Page 75); “Describe the effects of approximate error in
measurement and rounding on measurements and on computed values from
measurements.”
Materials for the Activity
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Oleic acid may be purchased from suppliers (e.g. Sargent-Welch: #WLC94631-06)
Olive oil or household oils can also be used.
Isopropyl alcohol is used to make the dilute solution of oleic acid and then dissolves
in water as a film of oleic acid forms on the surface of a tray of water.
Baby power or fine chalk dust can be used to confine the thin layer. Lycopodium
powder was once used for the activity but is an allergen for some students.
Large, circular, flat trays that have a diameter of approximately 40 cm are available
from food and catering suppliers such as: http://foodservice.chef2chef.net.
10 mL and 25 mL graduated cylinders. Pipettes can also be provided.
Medicine droppers.
Rulers, calculators, paper towels.
Jugs of water to fill trays with water and large plastic bowls to empty trays.
Activity document, calculation worksheet (with or without calculation hints).
Oleic Acid Teacher’s Guide (Large Tray Option)
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Possible Presentation Strategies
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Show Slides 1 through 14 of the PowerPoint presentation prior to the activity.
Show Slide 15 and 16 during a discussion of the calculation of the dimensions of the
thin film.
Show Slide 17 during a discussion of sources of experimental error.
Show Slide 18 during a discussion of the Big Ideas of Self Assembly worksheet.
Sample Calculation Results (Using Large Tray Dilution Volumes of 25 mL)
(Small Trays require solution volumes of 40 mL)
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The volume fraction of oleic acid in Solution #1 is 1/25.
The volume of oleic acid in Solution #1 is 0.04 cm3
The volume of oleic acid in 1.0 cm3 of Solution #2 is 0.04 cm3/25 or 0.0016 cm3
A group determines that there are 40 drops in 1.0 cm3 of Solution #2.
If 40 drops of Solution #2 had a volume of 1.0 cm 3, then the volume of oleic acid in
one drop of Solution #2 is 0.0016 cm3/40 or 0.00004 cm3.
The group estimated that average diameter their thin film of oleic acid was 21.50
cm and the average radius was 10.75 cm.
If: Area = 3.14 x R2; Then: The area of that film was 362.87 cm2
If Volume = Area x Depth; Then: Depth = Volume / Area. The thickness of the
example group’s film was determined to be 1.1 x 10 -7 cm.
The thickness of the thin film was then 1.1 x 10-9 m or 1.1 nanometers
Examples of Class Discussion Topics Include:
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Students will need to use a consistent strategy for reading the meniscus of the
liquid in graduated cylinders.
A solution must be thoroughly mixed before removing one cm3 needed to make a
more dilute solution.
Oleic acid dissolves in alcohol. The alcohol dissolves in water but the oil does not
dissolve in water leaving a thin film on the surface of the water.
The hydrophobic end of an oleic acid molecule has the structure of a hydrocarbon.
The hydrophilic end has the structure of a carboxylic acid.
The hydrophilic end of oleic acid includes an oxygen atom. The result in a very
unequal sharing of electrons with an adjacent atoms and the formation of partial
positive and negative charges.
The hydrophilic end of an oleic acid molecule includes highly electronegative oxygen
atoms and is asymmetrical. The hydrophobic end of the oleic acid molecule does not
include highly electronegative elements and is symmetrical.
Intermolecular forces referred to as hydrogen bonding describe the attractions
between the carboxylic end of the oleic acid molecules and the water in the tray.
Intermolecular forces referred to as van der Wall forces describe the interactions
between the hydrophobic ends of the oleic acid molecules as the oleic acid molecules
align themselves vertically on the surface of water.
Oleic acid is a pure substance and the thickness of a monolayer will also be the
length of an oleic acid molecule. Household oils are a mixture and the thickness of
the monolayer will then be the average length of molecules in the mixture.
Oleic Acid Teacher’s Guide (Large Tray Option)
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Examples of Student Responses to Questions
Question 1: How does your value for the thickness of the thin film compare with generally
accepted the length of 1.97 nanometers for oleic acid molecule?
 Student answers will vary. Many values will be larger or smaller than the generally
accepted values.
Question 2: Why might there be a difference between the thickness of the thin film that
you made and the generally accepted length of an oleic acid molecule?
 When student values are larger, that can mean that the thin film consisted of
multiple layers of oleic acid. When values are smaller, that can mean that gaps in the
thin film developed as the oleic acid spread to form a thin film.
Question 3: What are some sources of experimental error in the procedure you followed?
 Answers will vary and include inconsistencies in reading the meniscus of the liquid in
graduated cylinders, errors in counting the number of drops in a cubic centimeter of
a solution, difficulty in determining the average diameters of a somewhat circular
thin film, errors in multiplication or division, etc.
Question 4: How can experimental error for this activity be reduced?
 Answers will vary depending on what they have cited as sources of error.
Question 5: What area of the lake’s surface would be covered by a thin film if 1.0 liter of
pure oleic acid is accidentally spilled onto the surface of a lake?
 Set up a proportion to calculate the number of drops of oleic acid in a liter of pure
oleic acid: 1.0 drop / 0.00004 ml = x drops / 1000 mL. For this example, there would
be 25,000,000 (2.5 x 107) drops per liter. As a result, the area of the thin film
would be 2.5 x 107 times larger that the area from the activity.
 For this example, 362.87 cm2 x (2.5 x 107) = 9.07 x 109 cm2. There are 10,000 cm2
(1.0 x 104) in a square meter. The area would equal 9.07 x 105 m2. There are 1 x 106
m2 in a square kilometer. Therefore, based on this group’s results, the area of a
thin film of 1.0 liter of oleic acid would equal 0.907 square kilometers.
Oleic Acid Thin Film Resources
Web sites that provide information about oleic acid thin films include:
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www.chymist.com/size%20fatty%20acid.pdf
http://www.chemheritage.org/educationalservices/pharm/tg/antibiot/activity/size.htm
http://www.sargentwelch.com/pdf/opinstr/72701-81.pdf
http://chem.lapeer.org/Chem1Docs/OleicAcidLab.html
Web sites with information about Benjamin Franklin’s observations of a thin film include:
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www.benfranklin300.com/_etc_pdf/Dutch_Joost_Mertens.pdf
http://www.historycarper.com/resources/twobf3/letter3.htm
A book, entitled Ben Franklin Stilled The Waves, written by Charles Tanford and
published by Oxford Press included a full description of Franklin’s observations and
experimentation with thin films of oil.