Science Buddies: "Ask an Expert"

Doing Science Buddy Proj. https://www.sciencebuddies.org/ mentoring/ project_ideas/EnvSci_p016.shtml?from=Home. Tap water H2O is 7.5 ph, distill 5.0. We are doing acid rain effects on green beans. We want to have solutions at PH about 7, 6, 5, and 4. See matrix table in experiment above. Using tap H2O with 90ml tap water and 10ml vinegar PH drops to about 4.0! Test strip range goes from 7.0 - 4.0. Strips are from Germany and are called "Colorphast" and are submerging type. I don't know for sure, but a 50/50 mix would be very acidic. We could go PH about 7.0, 5.0, 3.0 and just use 3 plantings. We could get a broader range of test strips? Thanks for any guidance as we are getting close. Email is [email protected]

Hi,
I'm not entirely sure what your question is, but i will do my best to address your concerns.

I would suggest getting test strips or a pH meter that allow you to measure pH <4. Researchers who study the effects of acid rain routinely have used solutions with pH between 2 - 6.
For example see http://www.springerlink.com/content/p856g301638g7u72/
Tim Wood and F. H. Bormann
Water, Air, & Soil Pollution
Volume 7, Number 4 / April, 1977
Abstract ...Abstract Acidified precipitation may affect the productivity of forests by altering the availability of plant nutrients or by affecting the ability of trees to absorb and assimilate those nutrients. In this study, the short-term effects of simulated acid rain (pH range 5.6 to 2.3) upon the growth and nutrient relations of Eastern White Pine seedlings (Pinus strobus, L.) grown in a sandy loam soil were examined. . .
For more examples, run a web search for "simulated acid rain".

pH is a logarithmic scale, which means that a five-fold increase in acid concentration (H+ ion concentration, actually) does not result in a five-fold decrease in the pH value. Rather, a ten-fold increase in acid concentration results in a change of 1 pH unit. So, if you go from 10% vinegar to 50% vinegar, you might see less of a pH decrease than you expected. The actual change in pH will depend on other dissolved constituents in your water.

I hope that helps.
Chris