Science Buddies: "Ask an Expert"

hi. I am a seventh grader. I am measuring acid rain throughout my community to see 1. if there is acid rain here and 2. Does it vary in my county. I put out 15 jars all around.

My question is: I was going to collect the jars and test for acid rain after each rainfall. Should I do this or should I wait a specific number of days. Like maybe test the jars every three days no matter what.

And the other part of my question is how long does pH last If I don't test it right after the rain does the pH change over time
Thanks

Hi!

I think that you should collect the jars every three days. Also, the pH of the water will not change overtime, as long as you seal your samples. If you do not seal your samples, the water could evaporate causing a higher acid concentration in your samples.

Hope this helps!

If you are interested in answering the question of how much pH varies in time (from one rain event to another) then you would need pH data for each rain event. If you are only interested in the variation of pH from one location to another, then you might not need to know the pH of every rainfall event. However, the pH data for each rainfall event could possibly reveal trends that would not be seen in a 'bulk sample' that averages the contents of several rainfall events.

If it would be difficult for you to sample after every rainfall, and you are not interested in pH variation among rainfall events, then I think it would be fine to collect the samples every 3 days, or whatever time span seems reasonable.