Soil is a filter.

We’re studying soil now in earth science, which dovetails nicely with the farm program that I wrote about in my last post. Today the kids spent a surprising amount of time playing on a soil website, watching little animations and doing click-and-drag activities. I thought this would be pitched too young for Alex, but she and Colin both loved it.

Then we set up an experiment to understand how soil acts as a filter. The directions were confusing, and our results were not as spectacular as promised, but it still turned out to be a good activity.

We punched holes in the bottom of two paper cups. One was half-filled with sand, and the other had about an inch of sand and was then half-filled with dirt. We put each cup inside a smaller paper cup to catch any water that leached through the soil. We were supposed to see big differences between the sand and the soil, and we didn’t.

First we poured dirty water full of miscellaneous gunk into the top cups. The water that came out the bottom wasn’t clear, but it didn’t have any visible material anymore – the soil and sand filtered out all the cruft.

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Next we drained out both cups and started again with water that had been colored with purple food coloring. Alex hypothesized that the water that leached out into the bottom cup would stay the same color. Nope! It came out a light slate gray.

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The experiment directions promised all kinds of cool results, like the water coming out hot pink, and we were not at all that lucky. But it still got the main point across: soil filters some substances and chemicals out of the water that seeps into underground aquifers, but it doesn’t filter out everything.

Alex did a nice job with her lab write-up. I helped out by having her formulate the sentences orally first, so that I could dictate them back to her, but the essentials are hers. (Oh, and I wrote the tiny labels on the pictures.)

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4 Responses to Soil is a filter.

  1. Are you on Pinterest? I wanted to pin this one, along with the bread/earthquake demo onto my A STEM summer board. I know there’s a way to pin something without the “Pin me” button, but I don’t remember how. But maybe you don’t want your posts pinned? That would be perfectly understandable too.

  2. tinderbox says:

    I’m not on Pinterest, but I know other people have pinned my posts. I’m afraid I don’t know anything about how it works. I have no problem with you linking or pinning or reposting or whatever. :-)

  3. Challenge accepted!

  4. I think if you take one of your pictures and move it up in the post (so that it goes title: picture: text: etc.) you will end up getting more Pinterest traffic. (If you are interested in more traffic.) Right now, it’s pulling up your header.

    Can you see?
    http://pinterest.com/jennaandbruce/science-ideas/

    I learned about that trick from Chasing Cheerios. She had a great post about tiny adjustments that make blogs more Pinterest friendly.

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