What’s in dirt? It’s mostly little tiny bits of rocks and decomposed plant matter and worm poop and such, right? What if I told there’s usually a whole bunch of air mixed in there, too? Weird, perhaps, but also true. This experiment will show how much “empty space” there often is in the soil under our toes.
Jars + Dirt + Water = Science!
For this scientific demonstration, you’ll need a few clear glass jars, water, and what fancy folks call “soil samples,” but which we’ll just call “dirt” because it’s dirt. You’ll need as many different types of dirt as you have jars (or vice versa), so maybe don’t go get a Ball 20-pack unless you’re a professional landscaper or gardener.
Realistically, you can likely find at least three or four different dirt varieties in your yard. There’s the rich, black stuff that looks like stereotypical “dirt,” the drier, brown, sandy stuff, dirt with larger particles, dirt with small pebbles or gravel mixed in, maybe even some grayish, clayish stuff if you dig in the right spot. Depending on where you live, the dirt possibilities can be pretty wide ranging.
Once you’ve located all your different dirt types, loosely fill your jars about half full, each with a different sample. Then, top them off with water.
Before long, you’ll see air bubbles, um, bubbling up to the surface of the water. At the same time, the water level will be going down as the water takes the place of the escaping air in the dirt.
Science Me, Friendo
Kids (or whomever you’re doing this demonstration for) will notice that some types of dirt let loose way more air bubbles, and absorb more water, than other kinds. This shows the differing properties of different dirts—more bubbles, of course, indicates more trapped air and a “looser” overall composition. The denser dirt samples—like the clayish ones—will have less room for air in them than the lighter, “classic” dirt sample, for example.
The air “content” of dirt affects the types of plants that can grow in the dirt, as well as the ultimate health of those plants. Most vegetation prefers looser soil with more air pockets.
- 365 Super Science Experiments With Everyday Materials, E. Richard Churchill, Louis V. Loeschnig, and Muriel Mandell, 2001. ISBN 978-0806975610