If you want a science experiment model that is simple but still pretty cool then I would recommend the old classic: Model of the solar system.
It's a good idea because:
- You can use materials from around the house
- The facts are easily researchable (like what planets look like, where they are in relation to each other in the solar system)
- You can get as creative or complicated as you like.
Whatever you do, try to stay away from doing "amazing things with eggs".
This guy has a few cool tricks, but it's not going to get you a good grade, or is it?