Originally Answered: I need ideas for a science experiment for a science fair?
Kay, I did this great one where I learned how to make hot air balloons (you get a little pattern, replicate it 8 times, and then stick he pieces together). I used cellophane and scotch tape. Then I used simple math conversions so I had three balloons, one small, one big, one medium, and then I used a hairdryer to fill them with hot air and see which one would fly. The hairdryer didn't actually work too well... I needed somthing with more juice. I remember I found a solution, but I don't remember what it was.
AAAAnyway. I was only in the 5th grade when I did this project. It might be too simplistic, though the prep work involved makes me say "I don't think so." It wasn't that hard, just a little time consuming, and it was pretty fun.
Another project I did once in middle school was one where I asked "are teeth really destroyed by soda?" and I went to the dentist and asked for wisdom teeth that they'd removed from people. I got like 4 or 6, I can't remember, and then dropped some in glasses of different kinds of soda, two in water as a control. And a week later I checked to see what happened. The results were grotesque and totally awesome.
But I have avoided drinking much soda since then.
I enjoyed both projects. I think you can conduct them in a way that suits your age and grade level, even though I did rather cursory versions when I was young. They're good because they have good controls, and you don't have a zillion environmental factors affecting them.