[Specialk137]

At school, my group and I are currently comparing two water samples given to us in class, one being a sample from a creek, and another being a contaminated version.
We've found that the pH of the contaminated one is lower than the creek, being around 5, and that there is definitely copper in it (blue precipitate formed after the addition of Sodium Hydroxide)

I found on a website that metal ions make water acidic, but I was wondering if anyone could explain this further?
Any references to websites or textbooks would be great, I haven't been able to find anything so far.

[AWK]

Search for: acidity of metals cations

[ramboacid]

http://www.chemguide.co.uk/inorganic/complexions/acidity.html#top

This should cover most of your questions. If you are unfamiliar with coordination complexes, there is a link to another very informative page in the explanation on the site.