I decided to try this experiment that I saw on Pinterest this week - unfortunately it didn't work quite as well as I had hoped! The droplets in the ziploc were so small, that it was hard to show it to my kids. I also have shelves in front of my window, so they can't get close enough to it. It's a neat idea though! I also think it would have worked a lot better if my classroom was facing the sun for a larger part of the day.
Have you found any experiments that were really effective?