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The most time-consuming science fair project we did, in 2003, was our bean project. We decided to find out if great northern and pinto beans grew better or worse as we varied the pH of the water they were growing in. We used neutral to alkaline pHs of 7 to 9. But that was not all. You cannot add pure hydroxyl ions to a solution to increase the pH. You have to add a stable chemical, which is a cation (X+ or X++) bonded to one or more hydroxyl (OH-) ions. We also wanted to find out whether the chemical (cation) used to change the pH had any effect on how the beans grew.

We grew 13 vats of 18 beans each (9 pintos and 9 great northerns). One vat contained distilled water of pH 7.0 as the control. Then there were 12 more vats, one each for pH 7.5, pH 8.0, pH 8.5, and pH 9.0, for each of the three chemicals, calcium hydroxide, potassium hydroxide, and sodium hydroxide. We took bean height measurements every day for 40 days, and bean weight measurements at the end of the experiment. All in all, we had over 9000 individual data points!

We found that it does matter which chemical you use to change the pH, as well as what the pH is, to how the beans grew. They grew best in the lower pHs (8 and below), generally. They also grew best in the potassium solutions and worst in the sodium solutions.

By the end of this project we were pretty sick of beans, but it was a really good project, we learned a lot, and were chosen to go to the district science fair. We decided to put up a web page about our project so that maybe someone else will do a similar project for their science fair or get some ideas from what we did. We had quite a bit of trouble researching our topic, as there wasn't a lot of related information on the internet or in books. This page has one of our graphs and pictures of our bean setup on it, but if you want to know all about the project, you'll want to download a copy of our report. It is a 1 MB PDF file, so you can read it on any type of computer. You will need Acrobat Reader to read it (get it here if you don't already have it). Then click this link to download our report.

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