Model lab

Chemistry

Mitchell and Ben
Period 6, 2/19/10


I. Title: Polarity and Molecular Shape Lab

II. Statement of the Problem:

a. How shape affects polarity.

b. How elements combine to form molecules.

III. Hypothesis:

a. We hypothesize that based on the shape of a molecule we can determine whether or not the
molecule is polar.

IV. Materials:

a. Ball and stick model sets, pencils, paper, molecular shape chart (see fig. 1), and a camera.






fig. 1








V. Procedure:

a. We drew a Lewis structure based on the chemical formula.

b. Using the shape chart we determined the actual molecular shape.

c. We then made a model based on the actual molecular shape and the Lewis structure that we made.

d. Then we proceeded to determine if the molecule could be polar based on the shape of the molecule.

e. We then drew the model and took several pictures of the models.

VI. Results:

a. We took the following pictures.


Water: H2O

(Polar)





C2H4








C3 H8








BF3






SO3-2


(Resonance Structure)




VII. Conclusions:

a. We determined that it is not only the difference in electronegativity difference of the atoms in a compound that makes a compound polar, it is also the shape as is the case with H2O

b. A compound must have two distinctive halves so that one can be positive and the other can be negative.

c. We also determined the angle's between bonding groups and the shapes of all the molecules.

d. We learned that fluorine can cause molecule to have weird shapes due to it's high
electronegativity.

Chemistry

Mitchell

Period 6, 2/4/10

Ben

I. Title: The Paper Chromatography Lab

II. Statement of the Problem:

a. Which solvent would have the best retention time and separate the ink into pigments the best

b. The polarity of the solvents will have a significant effect on the retention time.

III. Hypothesis:

a. We hypothesize that the water will work better than the hexane, isopropyl alcohol, and methanol because water is polar and a smaller molecule than the others.

IV. Materials:

a. H₂O, CH₃OH, C₃H₇OH, and C₆H₁₄

b. In this experiment there are several dangerous chemical so goggles and aprons should be used. Also when using a fume hood one should keep their head away from the chemical and not put their head under the fume hood.

V. Procedure:

a. We filled one well of a 24 well plate with each of the four different solvents all with a similar amount.

b. We then took pieces of paper approx. 8 cm long and bent the paper at a 90 degree angle approx. 1 cm from the end.

c. We put four dots of black ink at the crease and did this with 4 different pieces of paper.

d. Then we put one piece of paper in each of the four well plates and observed as the solvent absorbed through the paper and separated the ink into the different pigments.

e. We then repeated the process only using one solvent (H₂O) and five different colored inks. These colors were orange, yellow, black, red, and green.

f. Again we observed the results.

VI. Results:

a. In the first part of the experiment we observed that water had the best retention time because it carried the colors the farthest.

b. The other solvents ranked as follows

2. CH₃OH

3. C₆H₁₄

4. C₂H₇OH

c. In the second part of the experiment we observed that while black, red, and green separated into different pigments orange and yellow did not. (see fig. 1)

fig. 1

VII. Conclusions:

a. Our hypothesis was supported by this experiment

b. This experiment supported our hypothesis because water carried the ink the farthest and separated it into pigments.

c. Water was the best with methanol being second best and hexane doing only slightly better than the isopropyl alcohol.

d. We also concluded that black, red, and green ink is a mixture of pigments while yellow and orange consisted of only one pigment.

e. This experiment demonstrates how the polarity of the elements compare to one another.

f. A possible error is that we didn’t get the exact same amount of solvent in each well. We also didn’t accurately measure the retention time.