Thursday, October 29, 2015

Water Retention

Gravel Water Retention
Water retention in different types of soils is one of those concepts where figuring out the process for the experiment is every bit as important as the actual results. I want the kids to come up with a way to test this on their own and be able to measure their results. They generally come up with lots of great ways to allow soil to absorb water, but they can struggle a bit when trying to make the amount of water absorbed measurable. The discussion of our plan oftentimes takes longer than our actual experiment. It's worth it, though, because it really makes them use their noggins! Eventually they come up with this...

To test water retention of different types of soils, we use a graduated cylinder, panty hose (which the kids think is hilarious!) and different types of soil. We put each individual type of soil (200ml) into the panty hose, SLOWLY add 200 ml of water, and figure our how much water was retained by the soil by looking at the amount of water than fell into the beaker. The kids are always surprised by how much water the sand retains!

Sand Water Retention
Top Soil Water Retention