Measuring the Size of an Oil Molecule

Grades: 9-12Subject: Nanotechnology

National Science Education Standards

National Science Education Standards

• Science and Technology: Content Standard E• Understandings About Science and Technology• Abilities of technological design

1What is Nanotechnology?

• Used in a wide variety of applications including: medicine, waste disposal and remediation, energy production and efficiency, electronics, manufacturing and consumer goods

What is Nanotechnology?

• A branch of engineering on molecular scales, typically less than 100 nanometers.

• Can help us understand how chemicals, water, and oil interact on a molecular scale.

Deep Horizon Oil Spill

What is a Nanoscale Object?• Human hair averages about one tenth of a millimeter (just

less than the thickness of a dollar bill)

So just how small is 100 nanometers in comparison?

How to Calculate Nanometers• Step 1: Convert to meters

100 nm = 10-7 m0.1 nm = 10-4 m

• Step 2: Subtract the exponents: 7 – 4 = 3, therefore the difference is 10-3 m, and 10-3 = 1/1000 = a thousandth

• Therefore, a hundred nanometers is a thousandth of the diameter of a human hair.

Time to Explore!Now it’s your turn!

The accuracy of your results will depend on the care and precision you take in performing the experiment.

Optional Preparation• Melt wax in the saucepan.• When entirely melted, run hot water over the

tray and dry thoroughly.• Carefully pour the wax into the still warm tray

and spread evenly across the bottom and sides.

Optional Preparation, continued• If using wooden levelers, dip one of the long

ends into the wax. Repeat for the second piece of wood.

• Ensure the wax is evenly distributed across the bottom and sides of the tray.

• Allow to cool overnight.

To Measure the MoleculePrepare the tray of water.• Pour distilled water into the tray until it is brimming over.• Use the small wooden wedges underneath the tray to

ensure it is level.• Place the levelers in the middle of the tray, until they are

about an inch from the ends.• Very gently sprinkle the powder onto the water surface.

Cover the entire surface between the levelers with a very fine coat of powder. If the powder is too thick, the oil will not spread properly.

To Measure the Molecule• Prepare the oil droplet.• Make a V-shape from the fine wire.• Tape the two ends of the V to the card so that a

portion of the wire remains protruding from the side of the card.

• Add the oil to the small dish or tray.• Dip only the very tip of the wire V into the oil.

To Measure the Molecule• Make the measurements.• Hold the oil droplet up to the ruler and estimate the

diameter of the oil drop. It should be exactly 0.5 mm, as measured with the micrometer (if available).

If the droplet is bigger than 0.5 mm it will spread too wide when added to the water. If it is too big, make it smaller by using a second piece of wire to pull away

small amounts of oil. If the droplet is smaller than 0.5 mm, record the diameter.

To Measure the Molecule• Make the measurements, continued.• When the droplet size is 0.5 mm or less, gently

touch the end of the wire V to the water. The droplet will spread out in the water.

• Then measure the maximum diameter (D) of the oil spread out on the water.

Calculate the Size of the Oil Molecule• Calculate the volume of the oil drop:

Assume that the drop is spherical in shape.• The volume of a sphere is:

Calculate the Size of the Oil Molecule• Calculate the area of the spread oil drop: To

calculate the area of the oil spread out on the water assume the oil is spread out in an approximate circle shape, so using D, the area equals:

Calculate the Size of the Oil Molecule• Calculate the thickness of the oil layer. • Since we know the volume of the oil drop, we

can work out the oil layer thickness from the formula for the volume of a cylinder: where height (h) equals the thickness of the oil layer.

Therefore,

What assumptions are made?• The oil molecule spreads across the water

until it forms a monomolecular layer only a molecule thick.

• The oil drop is spherical.• The oil patch is circular.• Unimolecular composition of the oil.

EvaluateA molecule of motor oil is about two times the diameter of an oleic acid molecule. If you use a drop of motor oil the same size as the one for olive oil, how would the size of the motor oil patch compare?

EvaluateDescribe two possible ways to improve the accuracy of your result.

If the average human height is 200 cm, and the distance from Los Angeles to New York is 4,000 km, what would be the distance from LA to NY if the human was shrunk to 100 nanometers?

Evaluate