Natasha, Max, Spencer, Sabrina, Jaffer and Melissa
June, 2010

Purpose
Test whether using a larger pan diameter produce the predicted length of a molecule of oleic acid

Equipment
30 cm Dish
Digital Camera
Lycopodium Powderexternal image IMG_2549.JPGexternal image IMG_2549.JPG
0.50 % Oleic Acid in Ethanol
Hexagonal graph paper (0.42 cm2 per hexagon)
Graduated cylinder (10 ml graduated in 0.2 ml increments)

Procedure
The experiment was carried out in two different groups, each doing five trials on two different days. First, we took the 30cm dish and filled half of it with water. Next, we placed the dish upon hexagonal graph paper, making sure that there was graph paper under the entire dish. We then took lycopodium powder, and lightly sprinkled it out over the surface of the water, avoiding clumps. Then, we put one drop of oleic acid in the center of the dish. The angle at which the oleic acid was dropped was not controlled, though it was less than 90 degrees to the surface every time. Then we waited until the oleic acid stopped moving (approx. 30 seconds) and then took a photograph of the dish (see Figure 1). We then dumped the dishes content in the sink and rinsed out the dish and repeated the above procedure 4 times.

To measure the volume of one drop of oleic acid, we used a graduated cylinder and counted how many drops of oleic acid there were per 1.0 ml. We then inverted the number of drops to get the number of one. After testing was finished, using the photographs taken of the dish (ex. Figure 1), we counted the number of hexagons that were visible from each trial (to the nearest quarter of a single hexagon) & recorded that information.

Our data table reflects 10 trials total (5 trials from two different groups). These trials were done at different times.

Figure 1:

IMG_2543.JPG

Data & Analysis
Table A:


avg of each trial
Number of Hexagons
Area of Oleic acid (cm2)
Length of Molecule (cm)
1
258.1
108.5
7.67618 x 10^-06
2
386.0
162.1
5.13817 x 10^-06
3
345.7
145.2
5.7384 x 10^-06
4
275.0
115.5
7.21212 x 10^-06
5
386.1
162.2
5.13484 x 10^-06
6
84.5
35.5
2.70841 x 10^-06
7
80.9
34.0
2.83065 x 10^-06
8
31.4
13.2
7.29653 x 10^-06
9
200.9
84.4
1.13966 x 10^-06
10
89.6
37.6
2.55429 x 10^-06


We only counted the hexagons that could be seen through an opening of the Lycopodium twice. In each trial we multiplied the number of hexagons by .42cm^2 per hexagon, giving us the whole area of the oleic acid. To find the actual length of one molecule we needed to know the volume of one drop of oleic acid. We found that there was 60 drops of oleic acid in 1.0 ml solution. Then we divided the drop by 200 giving us just oleic acid which was 0.000833. We divided that number by the area of the whole oleic acid area giving us the length of a molecule.

Uncertainty Analysis
We might have applied too much lycopodium powder to one side of the solution, causing the oleic acid to burst through the powder on the opposite side of the dish. Also, there might have been a minor discrepency in terms of adding up all the hexagons during the counting stage. The angle of the drop was also uncontrolled leaving possible discrepancy in the size and placement of the drop. In terms of numerical data, our lowest value of 1.14 multiplied by 10^-6 cm was closest to the data we got from using the smaller dish. However, we are confident that the real value is between 1 times 10^-6 cm to 4 times 10^-6.

Conclusion
A larger pan diameter does not give the expected value.