Polarity and Molecular Shape Lab

Lewis Structures and Ball/Stick Models


Triangular Planar, 90-109.5, non-polar




Tetrahedron, 109.5, non-polar




Trianguler Planar, 109.5, non-polar



Octahedral, 90, non-polar



Tetrahedral, 109.5, non-polar


Linear, 90-109.5, polar



Tetrahedral, 109.5, non-polar

Daniel Webster
Kody Berget

Polarity and Molecular Shape Lab

A. Statement of the Problem
1. How shape affects polarity
2. How to make ball/stick models of Lewis structures of molecular formula

We know that a molecules electronegativity difference affects it's polarity. Now we are going to see how an atom's shape affects it so, by contructing ball/stick models based on the Lewis structures of the molescules


B. Hypothesis
1. I hypothesize that the shape of the covalently bonded molecule will affect the polarity of the molecule. I will build ball/stick models to help prove this. I know that electronegativity difference affects a molecules polarity, and I will find if the shape of a molecule will.

C. Objectives
1. Construct models of molecules from their Lewis Structures
2. Determine polarity of molecules
3. Predict polarity of molecules
D. Procedure
1. Built model for each of the listed molecules on the data table and drew the Lewis structures.
2.. Drew the structures on the paper, using solid lines to represent bonds in the plane of the paper, and dashed lines for bonds that point back or forward from the plane of the paper.
3. Determined whether the molecular shape, bond angle, if its polar or not, and resonance.
4. Materials:










E. Results
1. The pictures of the models are in the above section.
2.



















Conclusion:

The shape does affect the polarity of the model, and a molecule must have two halves to be polar, one negative and one positive. The real difference thought between polar and non-polar molecules lies in the electronegativity difference, which also affects the orientation of the molecules shapes and angles. In conclusion, this lab was really helpful way to help us understand a molecules shape, and its polarity.

1)Explain how water's shape causes it to be polar
The two ends are both positive and and the shape is not linear, but bent.
2)Describes how water's properties would be different if the molecules were linear instead of bent.
It would probably be less polar, and the shape would of course be linear.

Discussion:
Daniel: This lab really helped us understand Lewis structure and shapes in covalent molecules. It helped us understand the relation between an atoms shape and its polarity. In another lab, we could also shape ionic molecules to help us understand the difference between the two types of molecules, and maybe next time use an electonegativity chart to help us with our lab.
Kody: In addition to what Daniel said I would like to note how this lab really help me, being a kid with ADD. The book stuff really didn't click to good for me, I mean I understood it for the most part but not 100 percent. When we did this lab it was some hands on learning so I found it to be more easily understood.

We are determining what solvent is most polar with the overhead pens
• What solvent is more polar or adhesive?
• What colors are pure substances or mixtures?
• What solvent reacts best to separate the colors?

We know that chromatography paper is used to separate the components of a liquid so that it can be identified. The dissolved colors move up the paper according to how well they attract to it or how adhesive the liquid is.


We hypothesized that H20 would be the most adhesive liquid because we weren’t sure what the other liquids were and we knew H20 was a polar fluid.

Materials we used in our lab:
• 9 strips of chromatography paper.
• Overhead pens: Red, Purple, Blue, Yellow, Orange, Green.
• Solvents H2O, CH3OH, C3H7OH, and C6H14
• 24 Well plate.
• Paper Towels
• Apron
• Goggles
• Notebooks

We used chemicals that could be hazardous to our skin and eyes. So we wore aprons and goggles. We also had fume hood vent so that we did not breath in the fumes the solvents let off.


Our Procedure started putting our safety equipment on such as our aprons and goggles. Then we cut 4 pieces of chromatography paper in the same lengths. We then made creases ¼ of the way up the paper and dabbed the black over head pen 4 times across the crease. We then filled our 24 well plate with the four solvents. We dipped the strips into the solvents making sure not to put the dot into the solvent but enough to let it wick up the paper. We waited 30 minutes and then recorded our results in our notebooks. H2O carried the ink farthest. So we agreed to use this for the next part of the lab. Repeat steps leading up to creasing the papers. This time you dot the separate papers with Red, purple, blue, green, orange, and yellow ink. We then filled the 24 well plate with H2O. We dipped the papers into the solvent and waited 30 minutes. Then we recorded our results in our notebooks. (See Results)




Results/Data:

Our hypothesis proved to be correct that H2O was the best solvent because it had the greatest polarity.
• Results: Water worked the best as the solvent then CH3OH came in second, then C3H7OH, and C6H14 was the worst solvent. The yellow color we used is a pure substance and the green, blue, red, and orange were mixtures.
• We learned that chromatography paper could separate components so they can be identified.
• Possible errors could be our chromatography paper being dipped to far into the solvent.