polarity and molecular shape lab

Introduction: In this lab we learned to build models of molecules in order to determine the shape and polarity of each molecule. To find the shape of a molecule you need to look at the number of bonding pairs and the number of un-bonded pairs. You can determine these pairs by looking at the lewis structure of the molecule. From the pairs you can determine the shape of the molecule. To find the polarity of a molecule you need to make a ball/stick model. If the ball/stick model contains exposed positive or negative ends you will know that the molecule is polar. We constructed models of molecules to determine the molecular shape and predict the polarity of each molecule.


Materials: Molecular model kit.
Pencil and paper.
Camera.
Brains.

Procedure: We built a model for each of the molecules listed on the data table on the back of our lab paper. Next we drew the three-dimensional structure of each molecule in Table 1, using 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. Then we noted the shape of each molecule in the third column of Table 1, the bond angles in column 4, whether or not they will be polar in column 5, and whether or not they exhibit resonance structure in column 6.

The Ball and Stick Models of Each Molecule:

C3H8:

CO2:

SF6:

IF3:

C2H4:

H2O:

H2O2:

N2:

CH4:

SiH2O:

HF:

SeF4:

SO3-2

 

BF3:

CH3NH2:

Conclusion: This experiment has taught us not only how to build a ball/stick model but also how to identify the shapes and the polarity of molecules. When you draw the lewis structure by itself it is more difficult to determine whether there are exposed positive or negative ends. Also, when you only draw the molecule on paper it is only in 2-D which makes it more difficult to see what the shape of the molecule truly is. Making the ball/stick model allows you to see the shape in 3-D which allows you to see the actual shape rather than try to imagine what it might look like in 3-D. This lab has been successful in teaching us about polarity and the shape of molecules. 

chromatography lab

Introduction:
Chromatography is a technique for separating mixtures. In this lab we compared different solvents' polarity and ability to separate a mixture into its pure components. Before we started this lab we had to know what solvents are used for. In our book we found that solvents are the substances in which the solute dissolves to make the solution. In this lab our solvents consisted of water, methanol, isopropyl alcohol, and hexane. We then took these solvents and used a piece of filter paper and markers to find out which solvent worked the best. Yahoooo!!


Statement of the problem:§ To determine which solvent will work the best to separate the pigments of ink from overhead pens.

Hypothesis:
§ We believe water would be the best solvent because of its strong bond and stickiness caused by its high polarity.

Materials:§ One color of overhead pen to test with different solvents.
§ Four strips of filter paper approximately 1cm. x 8cm.
§ Solvents: water (H2O), methanol (CH3OH), isopropyl alcohol (C3H7OH) and hexane (C6H14).
§ Well plate.

Procedure:Since we used potentially dangerous chemicals, we wore lab aprons and safety goggles at all times. We kept the potent chemicals under the fume hood as much as possible and disposed of them in the sink under the fume hood as well. We began our experiment by taking four of the eight strips of filter paper and made 90 degree creases about 1 ½ cm. away from one end. Then we put multiple black dots across the creases on each strip. We filled four of the wells in the 24 well plate, each with a different solvent. Next we placed one strip with the short end down into each different solvent making sure to keep the ink out of the solvent. After half an hour and keeping close observations, we carefully took the strips out and rinsed out the 24 well plate.
Then, for the second part of the experiment, we took the remaining four strips of filter paper and made creases just like we did in the first part of the experiment. This time, we marked one with green pen, one with red pen, one with orange and one with yellow pen. We put water in all four wells in the 24 well plate and put one strip in each of the wells, waited and made careful observations again for another half an hour. Then we recorded our observations for the first part of and the second part of the experiment.

Results:We found that water is the best solvent due to the fact that it carried the ink along the filter paper much better than any of the other solvents. On our second experiment, we observed that red and yellow are pure substances while green and orange are mixtures because when separated along the paper, it consisted of many different pigments. Bam!

Conclusion:

First of all, our hypothesis was correct. After analyzing our observations, we came to the conclusion that water was the best solvent and then methanol then the isopropyl alcohol and lastly hexane. We learned that water worked the best because it was polar and hexane did not work due to its non-polarity. Yes.