When we work out way through the Cycles Unit in Core Knowledge, we spend some time on Water Cycle. This experiment is fun and very visual for the little ones. I have used this with our 4th Grade buddies as partners and as in small groups as well. I've used this as an introduction to the water cycle and as an activity after we learned the steps. Both were fun.
The experiment and the worksheet are included. Sometimes, you may find that a few extra drops of food coloring are needed, so the children won't have to wait so long for the effect of rain. Prepare yourself for "OOOOHHHHS" and "AAAAHHHS" from the kids.