Re: Why does polyester cloth pick up oil better than cotton and a sponge?

Your question requires the definition of several scientific terms:

1. Hydrophobic: Does not like to absorb water.
2. Hydrophilic: Likes to absorb water.
3. Oleophilic : Likes to absorb oil.
4. Solvent : The liquid that something is dissolved into.
5. Solute : The material that is dissolved into a solvent.
6. Sorbent : The material used to absorb another material.

An ideal oil spill sorbent would be both oleophilic and hydrophobic. Two of the materials that you refer to in your question, cotton and sponge, are extremely hydrophilic. They absorb much more water than the third material, polyester. A good experiment to try would be to weigh out the same amount of cotton, sponge, and polyester. Make sure that the sponge is cut up so that it fits into the container and will rest on the bottom (this will facilitate absorption.) Do some testing, prior to showing the students, to help determine what amount of water will be fully absorbed by the sponge and use that amount for the experiment. Pour the known amount of water directly on the three sorbents and give them about fifteen minutes to absorb the water. After the fifteen minutes, pour off the water into a measuring cup to determine the amount of water that was not absorbed. You can then determine the amount of water retention by subtracting the amount of water poured off from the amount of water poured in.

The second part of the ideal oil spill sorbent is that is must also be oleophilic. The reason that the polyester is oleophilic is directly related to the material from which it is made. OIL PRODUCTS are used as the starting point for the manfuacture of polyester!!! We have a saying in Organic Chemistry, "LIKE dissolves LIKE." This mean that if a solute does not dissolve in water, then use a solvent that also does not dissolve in water. Now sorbents and solution chemistry are not the same thing, but they can be used quite nicely to explain why the polyester can pick up so much more oil. I would recommend a visit to the EPA website for even more information on oil spill sorbents:
http://www.epa.gov/oerrpage/oilspill/sorbents.htm

I wish you and all the future scientists in your class alot of luck learning about how cool science really is!!! I also think that the kids are really lucky to have a teacher that cares enough about learning to ask a really thought provoking question!!!

Regards,

A "Really Cool" Mad Scientist a.k.a. Dave Sherman