This event takes place outside, which makes cleaning up spills really easy. We divide our students into two large groups. One of the groups begins the day in a kickball tournament while the other group participates in Science Day. Halfway through, we switch. The students participating in Science Day rotate through centers, creating a science experiment at each one. All students take home "samples" from the experiment and a recipe sheet to make the experiments at home too.
All of the ingredients are pretty inexpensive and we usually get almost everything we need donated by parents. In addition to supplies, Science Day requires volunteers for each station. We usually use our classroom assistants and remediation support staff, but parents would make great leaders too.
You can find all kinds of great recipes online, but here's a copy of ours. If you're using a mac and having trouble with the download, you can try these tips. Alternately, you can just grab the plain word copy. Same recipes, just not as cute. ;) Do you have any great recipes to add?