It sounds like you are looking for experiments about compounds dissolving in water. Try including the word "dissolution" along with "water" and the grade level (or other appropriate words) in your internet search. The first page I found was:
undergroundadventures

I saw a science project about floating paper clips on water that amazed me. I didn't know it could be done.

What effects do you expect to see, of sand, paper clips, or pennies on water? Do you expect that any research has been done on this? What do you mean by: age appropriate? I am happy to try to answer, if I understand better what you are looking for.