molecule model lab

Title: Polarity and Molecular Shape Lab

Statement of the Problem:

How shape affects polarity.

How elements combine to form molecules.

Hypothesis:

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

Materials:

a. Ball and stick model sets, pencils, paper, molecular shape chart, and a camera.V. Introduction:
Because of the principle of outer electron shell repulsion, the electronegativity difference determines which type of bond any set of elements may engage in. For example, if the difference is more than 2.5 the bond is ionic if between .5 and 2.5 polar covalent, and if less than .5 nonpolar covalent. This repulsion also means that atoms in a bond will push one another as far away as is possible within the given bond.
VI. Procedure:

We drew a Lewis structure based on the chemical formula.

Using the shape chart we determined the actual molecular shape.

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

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

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

VI. Results:

See top of page.

Conclusion:

This lab is great for anyone who is a spacial learner. It helps them visualize what really happens with bonds.

Paper Chromatography Lab

Statement of the Problem
Test to see which solvent (mobile phase) works best in the fractionation of the mixture found in black ink.

Hypothesis
Water will work best in the fractionation of black ink because its molecules are polar and relatively small.

Materials
water, hexane*, methanol, isopropal alcohol, water-soluble overhead pens (black, red, orange, yellow, blue), Chromatography paper strips (10)1 cm by 8 cm, well plate
*be careful to keep the solvents under the fume hood and try to avoid getting too close to the poisonous gases that are emitted from these liquids.

Procedure
Fill one of the wells on the well plate half full with each of the solvents. Place the well plate with the chemicals underneath the fume hood. Take four chomatography strips and make a fold at a right angle approximately 1.5 cm from the bottom. Draw a pencil line perpendicular to the bottom of the strip and dot the line with the black water-soluble pen. Label the top of the chromatography strip with the name of one of the solvents. Place bottom of strips into corresponding wells. Wait approximately a half hour until each solvent has carried the ink to the top of strip or has stopped traveling up the strip. Repeat the previous steps starting with the folding of the chromatography strips using four well of the solvent that carried the black ink the farthest and using a different color pen on each strip.

Results
Water was the best mobile phase as it traveled the farthest up the chromatography strip and did the best job seperating the black ink to show the colors that made up the mixture. Hexane was the worst mobile phase as it did not seperate the black ink at all.

Conclusion
I accept my hypothesis because it was proved to be true that water was the best solvent as it carried the water the farthest up the chromatography paper and did the best job at fractionating the black ink. Hexane was the worst. It did not manage to fractionate the ink at all. The methanol and isopropal alcohol were in the middle, because they did not carry the fractionated ink as far up the chromatography strip as the water did. Hexane was the worst solvent because it is nonpolar and not sticky enough to break down the ink. The ink was a mixture and that is why it fractions into an array of colors. Hexane was not appropriate for the second part of the lab as it did not fractionate the ink. I discovered that yellow, red, and blue are pure substances; while, orange and black are mixtures.