Testing Liquids for polarity Essay

Custom Student Mr. Teacher ENG 1001-04 17 November 2017

Testing Liquids for polarity

Results and Observations:

Liquids

Results

Shape of molecule or Lewis Structure

Conclusions

Distilled Water

4 cm of deflection

The water molecule is very polar. This is because the only oxygen in the molecule is left with 2 lone pairs which give as a result an enormous negative center. On the other hand, the two H atoms are positive resulting into a very polar molecule. As a result, the stream of distilled water has a quite large deflection which almost went out of the beaker.

Heptane

2 mm of deflection

The deflection is very small, almost impossible to detect. Because of this we can conclude that this molecule is non-polar as no attraction towards the charged ruler is shown.

Ethanol

3 to 4 cms of deflection

In this case, the deflection of the stream is bigger and more obvious to human eye. As we can see in the structure of the molecule, the oxygen atom is left with 1 lone pair which makes it into a medium size negative center. However all the carbons and the hydrogen atoms in the left of the oxygen exert a positive charge bigger than the negative charge which makes it polar. However although there is polarity, the stream isn’t deflected so much.

Propanol

3 cm of deflection

Although the structure of this molecule is quite similar to the one of HEPTANE, in the case of PROPANOL, we can see an oxygen atom which again is left with 1 lone pair1 which creates a negative center in the right of the molecule. However, this negativity is balanced thanks to the C and H atoms in the left. This is way this molecule is polar but not enough to deflect the stream so much. This is why it shows a medium deflection of 3 cms.

Propanone

2 cm of deflection

This molecule shows as very weak polarity because the only way of this molecule being polar is the double bonded Oxygen-Carbon bond. Oxygen is more electronegative than carbon which gives as a result a very weakly charged dipole. In conclusion, the stream won’t deflect a lot.

Ethanoic Acid

5 cm of deflection

In the case of this molecule, we can see 2 O atoms which in total are left with 3 lone pairs which create a gigantic negative center. The rest of the atoms of the molecule aren’t capable of dealing with these forces so the molecule turns out extremely polar. This is why we can see a very big deflection in this case.

Ethyl acetate

3 cm of deflection

This is a moderately polar molecule which shows a medium deflection of the stream. This is because although it has 2 O atoms one of them located on the top of the molecule, the lone pairs of these O atoms can’t exert that big amount of negative force as to create a very polar molecule. Another factor is the presence of H and C atoms in both sides of the O atoms which balance the forces of the lone pairs. In conclusion, although it’s a polar molecule, due to the position of the O atoms and the H and C atoms, Ethyl Acetate didn’t deflected that much the stream

Ethane-1,2-diol

4 to 5 cms of deflection

This molecule is clearly polar because of the great deflection that is caused by it. There are two O atoms each one with a lone pair which creates a very powerful negative center which makes the molecule to be polar.

Increasing Order of Polarity Downwards

HEPTANE

PROPANONE

PROPANOL

ETHYL ACETATE

ETHANOL

DISTILLED WATER

ETHANE-1,2-DIOL

ETHANOIC ACID

Camilo Lovera Trujillo Testing Liquids for polarity

Evaluation / Improvements:

Limitations / Errors

Improvements

* Bad smell of substances.

* Many of the substances we were working with, had a very strong and bad odor which spread all the way over the class. Due to this smell, many of the students found difficult to concentrate and to be able to record correctly the deflection of the streams. It’s better if the students wear any type of mask or mouth covering so that focusing of students isn’t affected by the smell.

* Electrically-charged rod

* For being able to deflect the stream of the substances it was necessary to have an electrically charged rod which could attract the stream However, is difficult to keep a fair test in charging the rule or the rod because it was possible that in some cases, the rod was more charged than others. A possible solution to this is to change the rod for a magnet or and object which is already magnetized so that the same attraction force is kept during all the experiment and no possible inaccuracy in the deflection of the streams can happen.

* Deflection

* The deflection, in some cases, was difficult to record. Unfortunately, we had no instrument to measure the deflection but our own eyes. It was possible to use the ruler but it was also very difficult as everything happened very fast. Due to this, there might be some inaccuracy in the results as they were recorded with what we saw and estimated to be the deflection. Maybe a way to help recording more accurately the information is to use instead of a beaker, a kind of deep transparent tray placed over a ruler so that is easier to measure the deflection

Camilo Lovera Trujillo Testing Liquids for polarity

Conclusion:

In conclusion, this practical helped us to find the relationships between the Lewis structure or the molecule structure and the deflection the substances caused when they were near to an electrically-charged rod. From the observations and results we can also conclude that the C atoms reduce the polarity of the molecules as they created positive center in the molecule. However, it was thanks to the O atoms n most of the molecules that their polarity was considerably increased as they were left with lone pairs which helped to create negative center even bigger than the positive ones and due to this, deflect more the streams. On the other hand, there’s a final conclusion to be made and is about the order of the polarity. Acids are the most polar substances just after the amides. In the case of Ethanoic Acid, we can see that it makes part of the most polar substances tested in this experiment as a result of the H bondings and the presence of the 2 atoms of O. Going down the list we will find: Alcohols, Ketones, Aldehydes, Amines, Esters, Ethers and Alkanes.

Camilo Lovera Trujillo Testing Liquids for polarity

Bibliography for Images of Lewis Structure and Molecular Structures:

* http://www.chem.purdue.edu/gchelp/molecules/heptane.gif

* http://www.uni-saarland.de/fak8/schneider/anichem/struktur/ethanol.gif

* http://www.fisicanet.com.ar/quimica/organica/ap1/propanol01.gif

* http://www2.open.ed.jp/data/37561/01/1221system/images/CH3COCH3.jpg

* http://scienceaid.co.uk/chemistry/organic/images/ethanoicacid.jpg

* http://www.steve.gb.com/images/molecules/alcohols/ethane-1,2-diol.png

Bibliography for additional Information:

* http://www.elmhurst.edu/~chm/vchembook/213organicfcgp.html

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