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 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
 Oleic acid may be purchased from suppliers (e.g. Sargent-Welch: #WLC94631-06)
Olive oil or household oils can also be used.
 Isopropyl alcohol.
 Baby power or fine chalk dust can be used to confine the thin layer.
 Dinner size or large tray
 10 cm3 and 25 cm3 or 50 cm3 graduated cylinders.
 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 Teaching Strategies
Show a PowerPoint
 Show Slides 1 through 12 of the PowerPoint presentation prior to the activity.
 Show Slide 13 and 14 during a discussion of the calculation of the dimensions of
the thin film.
 Slides 15 through 21 outline the process of the formation of a thin film.
 Slide 22 poses questions for students.
 Slide 23 and 24 present the Big Ideas of Self Assembly.
 Slides 25, 26 and 27 provide information for teachers.
Discuss terms that describe a solution.
Discuss relationships among the volume, thickness and area of the top surface of a
disc.
Preview the calculation worksheet and sample calculations.
Discuss Experimental Procedures:
 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.
Discuss the chemical structures and properties of water, oleic acid, and alcohol.
 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 were 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:
 www.chymist.com/size%20fatty%20acid.pdf
 http://www.chemheritage.org/educationalservices/pharm/tg/antibiot/activity/si
ze.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:
 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.