Water's Polarity

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We have all seen the bending water trick with a comb charged with static electricity from combing it through hair. If you hold it near a stream of water, the stream of water will bend.

Have you ever compared it to a steam of oil?

Since you don't have a running stream of oil in your house like a running stream of water, you'll have to use a Styrofoam cup. Take a pen and poke a small hole into the bottom of the cup. You might want to fill it with water first and run that experiment first. Take a comb and vigorously comb your hair. Then bring the comb teeth near the stream. Now fill the cup with vegetable oil instead of water and run the experiment again. You should see that the water bends toward the comb, but the oil stream is unaffected.

Why the difference?

The chemical bond that water has between the oxygen atom and the hydrogen atoms is a covalent bond. Remember that a covalent bond result when atoms with a molecule share their electrons. As it turns out, oxygen is stronger at pulling on electrons than is hydrogen so the oxygen atom will end up with the electrons more often than will the hydrogen. This is called a Polar Covalent Molecule. In this experiment, the negative charge on the comb attracted the small positive charges on the hydrogen atoms in the water molecules. This the water molecules all turned around so that their hydrogen atoms pointed toward the comb. The mutual attraction between the small positive charge on the hydrogen atoms and the negative charge on the comb was strong enough to bend the water stream toward the comb.

But what about the oil?

The atoms in the oil are non-polar, and therefore are not affected by electrical charges.

source: Exploring Creation with Physical Science, Jay Wile