a Question for TEACHERS

for my new internship i need to find out some really cute science fair projects for children in grades 3-5...

any ideas would be so helpful!

Thanks!!

These are some that my kids did last year:
what cleans a penny best?
using lemons to light a small lightbulb
what cereal brand has teh most raisins?
What uses more water a shower or a bath?
What type of food do ants prefer?
what brand of garbage bags can hold the most garbage (or amount of weight)?
What brand of paper towels absorbs the most water.