43000

Questions about science experiment results [Georgia] 

November 10, 2006

Hello,
Great site! My Uncle and I have just completed the majority of my 8th grade science fair project experiment. We wanted to know what rusted steel wool the quickest: water, sugar water, salt water, vinegar or Clorox. I know you have received inquiries on this type of experiment many times and we have benefited from it greatly. I have some additional questions on the subject that I cannot find answers to however. First, our procedure: We cleaned the steel thoroughly (thanks to tips from this site-- it will be heavily mentioned in our report/bibliography!) and partially submerged them in a 10 ounce clear plastic cup containing 8 oz of the liquids mentioned above. To limit spillage, we taped another cup, with a 1/4" hole in it, on top of the other cups. The hole was there to allow moisture in. In a week, here are the results from least to most rusty:
1) Sugar water
2) Water
3) Salt water
4) Vinegar
5) Clorox
Note: Water was NOT out of the tap and therefore was not aerated nor contained chlorine.
The difference between the first three was minimal. The difference between Vinegar and the first three was very significant as was the difference between the Clorox and the other four (the entire biscuit of Steel Wool [link is to product info at Rockler] was nearly converted into rust!).
Here are my questions:
Early in the experiment, we noticed that the cups containing the vinegar and Clorox were dripping with condensation. Did the Clorox and vinegar know that this was a rust experiment and that we would need water???? Also, after a week, there was absolutely no scent of Clorox or vinegar in the cups at all. They smelled and looked like water!
Furthermore, the rusting was still occurring in the cups containing vinegar and Clorox but the rate had decreased to that of the other cups. I think that water replaced the vinegar and Clorox but don't know why. Your input is greatly appreciated.

Aron H. and Eddie J.
Student - Columbus, GA, USA

Vinegar and chlorox are both acidic. The acid reacted with the steel. Acetic acid plus iron will yield an iron acetate. Chlorox is a 5% solution of sodium hypochlorite, NaOCl. This is a moderately stron oxidizing agent. Rust is iron oxide, so you would expect it to form the most rust.
Rust is formed by iron plus oxygen plus moisture. It takes all three. temperature is a factor on the rate of reaction within certain limits. The reaction will proceede faster when you have material that increases conductivity. Sugar is a very poor conductor.
Hit google for rust and then oxidation. Wikepedia should have some layman's language on both.
The smell went away because you used up the free acetate and free OCl.

James Watts
- FL