Use popcorn, and see how water in the environment has an effect over a dry environment.
Here's what you get....
First set it up exactly the same.
Some corn on a wet paper towel, covered by a wet paper towel. Then covered with tin foil.
Do the same thing with 2 dry paper towels, and cover with tin foil to give your experiment the same atmosphere, minus the water.
Keep it in the same place on the counter, and every day at the same time look at them to compare the differences. Write down your differences each day.
We started to see the corn swell up in the wet atmosphere.
And 9 days later..... CHECK this out!