# NCLT`s Construct-Centered Design and the Oleic Acid ```The following is an adaptation of NCLT’s Construct-Centered Design to the Oleic
Acid thin film activity.
Step 1: Select the big idea:

Two chemical substances will self-assemble into a structure with a
nanoscale dimension.
Step 2: Identify the grade level of the students.

Middle school and high school students with poor to average mathematical
skills.
Step 3: Unpack the big idea (construct)





The unique structures of water and oleic acid molecules results in the
formation of a thin layer of oleic acid on the surface of water.
Students will have prior knowledge of attractive and repulsive electrical
forces.
Students may believe that a chemical reaction has taken place.
There is a nine step sequence of measurements and calculations.
The big ideas of self-assembly include:
1. Mobile structural components
2. Target is low energy equilibrium state
3. Ordered structures
4. Assembly through attraction or repulsion forces between the
components
5. Environment selected to induce designed interaction
6. Components retain physical identity through and after
7. Reversible by controlling the environment
Source: Whitesides and Boncheva (2002)
Step 4: Create a claim
There is series of nine steps that lead to the calculation of the thickness of the
oleic acid layer. Students will be able to:
1. Write the fraction of oleic acid in 1.0 cm3 of the first solution. Put the
volume of oleic acid in the numerator. Put the total volume of the solution
in the denominator.
2. Change the fraction of oleic acid from Step 1 to a decimal form. Divide the
numerator in Step 1 by the denominator in Step 1.
3. Determine the volume of oleic acid in 1.0 cm3 of the second solution. Divide
your answer to Step 2 by the total volume of the second solution.
4. Record the number of drops in 1.0 cm3 of the second solution.
5. Determine the volume of oleic acid in one drop of the second solution.
(Divide the answer to Step 3 by the number of drops recorded in Step 4.)
6. Record the average radius of the circular area of the thin film (in
centimeters). The average radius is half of the average diameter.
7. Calculate the area of the thin layer of oleic acid (in square centimeters).
Use the formula for the volume of a circle. Area = () x R2. C
8. Calculate the thickness (depth) of the thin layer of oleic acid (in
centimeters). Use the formula for the calculating the depth of a cylinder:
Depth = Volume / Area
9. Convert the thickness of the layer of oleic acid from centimeters to meters.
Remember that a centimeter is 2 Powers of Ten smaller than a meter.
Step 5: Specify what evidence you will expect that a student has the desired
knowledge.

Students can describe the formation of a thin film of oleic acid as a selfassembly process resulting in a structure with a nanoscale dimension.
Step 6a: (assessment): Design particular tasks, questions, or situations
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Students can compare their data with those collected by other students
and suggest possible sources of error.
Students can be asked to determine the area of water over which a large
volume of oleic acid will spread.
Step 6b: (instructional materials): Design particular learning activities (learning

The students could watch the oleic acid module and then be asked to
construct a report describing the process y which oleic acid formed a thin
layer.
Step 7a: Review assessment tasks.

Present a scenario to students prior the activity where students are asked
to determine the average thickness of a layer of paint if one liter of paint
covers and area of 10 square meters.
Step 7b: Review learning tasks.

Determine the extent to which students have an understanding of
molecular structures.
```