Polarity and Molecular Shape

By doing this blog, we are attempting to figure out the most probable structure for each given molecule. Prior to this lab, we had been taught about Lewis Structures and how to figure out each one for any given molecule. Since the ball/stick model of a molecule is basically the same as the Lewis Structure, it was quite easy to figure out the most probable shape of each molecular formula.

Hypothesis:

I hypothesize that the ball/stick model of a given molecule will resemble, if not replicate, the Lewis Structure of that same molecule.

Materials:

Ball & Stick model kit including:

• 20 Rigid Green tubes-Covalent bonds
• 6 Flexible White Tubing
• Various Colored Balls
• 4 red two prong-Oxygen
• 12 white one prong-Hydrogen
• 6 green one prong-Halogens
• 6 black 4 prong-Carbon atoms (can also be nitrogen or silicon)
• 1 pink 5 prong-Iodine/Selenium
• 1 gray 6 prong-Sulfur
• 1 blue 3 prong-Boron

Safety Procedure?:
Although we are not working with hazardous materials in this lab, you must still be aware of the balls and sticks so this lab does not result in the injuring of your eye or other such sensitive areas.

Procedure:
In this experiment, we created a Lewis Structure for each of the molecular formulas provided to us by our instructor prior to beginning the lab. For each Lewis Structure that we made, we had to construct a ball and stick model representing the 3-D structure of the given molecules. Also, according to the repelling groups and the unbonded pairs, we had to decide what the actual molecular shape was. Following this, we had to decipher the bonding angle and whether or not the molecule was polar.

Results:
As you can see in the adjacent images, the Lewis Structure of H2O (right) is represented by the ball and stick model (left). For the remaining molecules we did basically the same thing, for each we found the Lewis Structure and built its ball and stick model.












Conclusion:
According to our results, we accept our hypothesis. Each Lewis Structure drawn had a corresponding ball and stick model that presented the 3-D view of the molecule.
From this lab we have learned the different structures and angles that each molecule result in from the different bonded elements. This could be used in real life by knowing the potential stability of different molecules to further our knowledge and perhaps lead to a future discovery.
Errors that we have come across is that we weren't absolutely sure about the polarity of each molecule.

Polarity of Solvents Acting on Different Pigments of Ink

Which substance has the most polarity?

• The more electronegativity an element has, the more polar the element is.

• In non-polar bonds, the electronegativity ranges from 0 to 0.5.


• Once reached 0.5, the bonds turn to polar until it reaches 2.1 in which it then turns to an ionic bond.

Hypothesis:

To begin our experiment, we hypothesize that H2O will draw the ink further up the chromatographic strip than any of the other three solvents. H2O is expected to be the answer to our question; which substance has the most polarity?


Materials:

Solvents:
Methanol
H2O
Hexane
Isopropal

Remaining Materials:
1 24-Clear Well plate
8 Strips of Chromatography Paper
1 Black Dry Erase Marker
4 Various Colored Dry Erase Markers (Red, Green, Orange, and Blue)
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Safety Procedure:

When working with the solutions included in this lab, be aware of your surroundings and always wear your safety equipment (goggles and aprons). It is essential that you properly use and handle the given solvents as they are all (besides H20) skin and/or lung irritants and should be kept under the fume hood and away from your face as often as possible.

Procedure:

In this lab we measured the ability of a solvent to separate ink based upon the solvent's overall polarity. First, we prepared a water well with four different solvents (Methanol, Water, Hexane, and Isopropal) each well containing a few drops of each solvent. Then, we began by cutting 8 strips of chromatography paper and then marking then folding them about a third of the way down and also penciling a line alone the crease. Next, we dotted a line following the pencil line and then placed the paper in the dish of the certain solvent. We then waited as we watched the ink spread on the paper, water being the most polar showed the ink spread the furthest up the chromatography paper.
The second part of the lab we chose one substance to put four different colors to compare which color would go the furthest up the paper. In our case we chose water to determine what ink went up t he furthest.


Results:

In the lab, H2O (water) was the most polar substance therefore brought the ink up the chromatography paper the furthest. The other substances did not move up as fast or separate as well as the black ink did with water. We noticed that when we used other solvents, it took longer to travel up the paper. Water was the leap contender because it is a polar molecule, which is why the ink traveled so far up the paper.



(Journal Entries)



Conclusion:

Based on the evidence, we accept our hypothesis that H2O is the most polar.

When we used water with the chromatography paper, the ink was drawn the farthest up the strip in relation to the other solvents we used. We also figured that black ink "broke down" the best, because black is the presence of all colors and they all separated out the fastest compared to the other colors such as red, blue, green, and orange. When we used water to compare the second time, this time using all the colors which water, we found out that the colors separated and moved up the paper faster. In conclusion, water was the best polar molecule between methane, isopropyal, and hexane.