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choicefresh 04-07-2006 04:58 PM

~*need help on materials for science project*~
 
I am doing a project on what is in the drinking water of different schools' drinking fountains. I was thinking I could get a water tester to see what was in the water. I've looked on Google, but most of them are either too expensive, or do not have a lot of uses.

sciencefreak 04-07-2006 11:48 PM

Well, one test could be an acid or alkali test...u could buy litmus solution or make your own using red cabbage. It's really simple - shred the cabbage and boil with water. strain the juice and it's your very own home-made tester!!!

sciencefreak 04-08-2006 10:43 PM

I think you're a bit confused, so here's something more to make it easier....

Red cabbage contains a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purplish color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.

The color of the juice changes in response to changes in its hydrogen ion concentration. pH is the -log[H+]. Acids will donate hydrogen ions in an aqueous solution and have a low pH (pH < 7). Bases accept hydrogen ions and have a high pH (pH > 7).

Here is a table of approximate colors of red cabbage indicator solution at different pH's. If you wish, make your own chart, using chemicals of known pH.

sciencefreak 04-08-2006 10:44 PM

If you don't want to use the liquid indicator, you can make your own pH paper strips using red cabbage indicator. Take filter paper (or coffee filter) and soak it in a concentrated red cabbage juice solution. After a few hours, remove the paper and allow it to dry (hang it by a clothespin or string). Cut the filter into strips and use them to test the pH of various solutions.


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