Polarity and Molecular Shapes

OBJECTIVES:
-Construct models like molecules
-Determine molecular shape
-Predict polarity of molecules
MATERIALS:
-Molecular Model Kit
PROCEDURE:
1) Build a model for your selected molecules.
2) Draw a three-dimensional structure of each molecule . Use solid lines to represent bonds in the plane of the paper, dashed lines for bonds that point back from the plane of the paper, and wedged lines for bonds that point out from the plane of the paper toward the viewer.
3) In a table, note the shape of each molecule, the bond angles, whether or not they will be polar, and whether or not they exhibit resonance structure.
ANALYSIS:
1) Explain how water shape causes it to be polar.
2) Describe how water’s properties would be different if the molecules were linear instead of bent.
3) Based on the results of this experiment, list the molecules from the experiment that would be water-soluble.
Here are some examples:
C2H4
compares to

C3H8

Chromatography Lab

Statement of The Problem-

Out of four solutions, which solvent will have the most effect on drawing out the pigments in each color?

The purpose of the Paper Chromatography Lab is to compare different solvents’ polarity and ability to separate a mixture into its pure components.

Solvents:

H₂0

CH₃OH

C₃H₇OH

C₆H₁₄

Materials-

(Part 1) Black over-head pen (Part 2) Red, Yellow, Green, Purple, and Purple pens.

Solid Phase: 10 Chromatography paper strips

PART 1 Procedure-Test to see which solvent works the best in the separation of the mixture found in black ink.

1) Pick one color over-head pen (black) to test with different solvents.

2) Cut four strips of filter paper approximately 1 cm x 8 cm

3)Make a right angle bend at the end of the paper approximately 1.5cm from one end.

4)Put a pencil line near the crease and dot the ink to be tested several times on the pencil line.
(allow a few seconds between dots for ink to dry)

• Using pencil, label each strip as to which solvent will be used.

5) Fill 4 separate wells on the 24 well-plate approximately 1/2 full of the solvents.

6) Place your paper strips into the wells so that the short end is in the solvent.

7) Allow the solvent to wick up the paper for approximately 30 minutes. Record your observations.

Results-Conclusion

Out of the four solvents, H₂O left the longest trail of ink, in the fastest amount of time. CH₃OH followed slightly slower and did not bleed out as far as water. C₆H₁₄ came third, this solvent is not as polar as the first two, so it made sense that it did not reach the same distance. C₃H₇OH is not polar what-so-ever, therefore, did not bleed out at all. In this case, H₂O was the best solvent you can use for this lab since the only other solvent that worked somewhat decent was CH₃OH.

PART 2 Procedure- Choose a single solvent from Part 1 and test its ability to separate different colors.

1) Repeat steps (1-4) outlined in the above procedure with different colored inks. (4-5 strips depending on how many colors you use)

· Be sure to label the strips into the wells so that the short end is in the solvent.

4) Fill 4-5 wells half full of the solvent

5) Place your paper strips into the wells so that the short end is in the solvent.

6) ALLOW THE SOLVENT TO WICK UP THE PAPER FOR APPROX. ½ HOUR.