Polar vs. Nonpolar Compounds
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Chemical Concept Demonstrated
2 burets are filled with the polar and nonpolar liquids of your choice.
(Suggested: hexane for the nonpolar, water for the polar)
A small stream is made to exit each buret.
Charge a rubber and/or glass rod using pieces of silk or fur. Hold the rod next to the streams of the burets.
The nonpolar liquid doesn't do anything. The polar liquid, on the other hand, deflects significantly to the side.
The charge in the rod only affects the polar liquid because the polar liquid contains molecules with an unequal charge distribution (a dipole moment). For example, a water molecule has a significant negative charge concentration on its oxygen because a majority of the molecule's electrons are around the oxygen molecule.
The charge in the rod attracts either a positive or negative charge and repels the other. In nonpolar liquids, the positive and negative charges are spread evenly throughout the individual molecules, and the resulting attractive and repulsive forces balance each other out. In polar liquids, however, the uneven charge distribution in the liquid's molecules means that the attractive and repulsive forces will not balance each other out, and the liquid will deflect upon encountering an electric field (such as the charged rod).
- Dr. George Bodner (Perdue University)