Science Buddies: "Ask an Expert"

My child ( grade 5 ) is doing a science project - Metal Oxidation.
The metals used are Aluminium, brass, Copper, Steel ,Zinc in both Salt and plain water.
The first metal to oxidize is Steel in Salt Water. We have conducted some research on why metals oxidize faster in salt water than plain water.
Would there be a good explanation at grade 5 level for her to explain why it happens?
Also, why would copper make salt water green in color whereas it doesn't change the color of plain water?

Hello and welcome to the forums!

I found some links (searching for "rust") that might help: http://en.wikipedia.org/wiki/Corrosion; http://en.wikipedia.org/wiki/Electrochemistry; http://science.howstuffworks.com/question445.htm.

While most of these descriptions is above grade 5, it would be good if your student can explain what is happening and the term "electrolyte".

With regards to the copper, the salt in the water makes the water a better electrolyte, which means that the oxidation speeds up and occurs in a short enough time for you to observe it.

Keith