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Name: Lydia
Status: student
Grade: 6-8
Location: FL
Date: December 2007


Question:
My 7th grade daughter is doing a project on 5 metals and how do they react in salt water, fresh water (lake), and tap water (well). We noticed the aluminum, brass, and stainless steel did not react to any of the waters. The plain steel started to actually corrode and grow stuff on it, in all 3 waters. The copper, which is neat, turned green and turned the water green in the salt water only. All I can figure out and find on the net is this - fresh water and well water is mostly deionized and has a minimum of ions. Salt water has a high amount of ions, and the ions start to interact with the salt particles causing a reaction. Is this correct or did I come to a wrong conclusion? I still do not have much more of a conclusion other than that. Can anyone explain to me WHY copper does this, and why the others do not?



Replies:
Lydia,

The right path to finding the answer of why copper turns the salt water green is knowing in which specific ions salt water is rich. The answer is that salt water is rich in sodium chloride ions. Specifically chloride ions will form copper chloride, which will turn the water green. Copper sulfate is also another common water-soluble copper salt--this would turn water brilliant blue. The other metals either do not form water soluble salts, or do not form salts that are highly colored.

Matt Voss



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