Carbon Electrodes

[Voice]

G'day, I am sure that someone can help.
I have a Year 9 prac. which requires carbon electrodes. Students are just testing to see if distilled water, water from the tap, salted water and sweetened water conduct electricity. They are supposed to use Carbon electrodes in the prac. As the electrodes are a constant should it matter if I substitute both electrodes with Zinc or both electrodes with Copper?
I wouldn't have thought so, but I have decided to check.
Thanks for any help.
Maree

[smiley]

The benefit of carbon is that it won't react/rust etc in the water. Other electrodes will work, so it's really a matter of how long the circuit is connected. Long enough to see a light/read a meter should be fine. Be careful around salted water, because they can make chlorine from the salt! (Like swimming pools really)

[Voice]

Thank you Smiley.
You have articulated my own thoughts.
Maree

[smiley]

Go copper rather than Zinc - less reactive! And I'd do the salt solution last. We do that here too, and salt goes last, so that there's no cross contamination from salt to sweet, which would then give a false positive result.