Basic peg board circuitry; baking soda volcanoes.
electricity, chemical compounds and acid
structures
Decomposition, energy, light, electricity, and photosynthesis are all good science fair topics
Evolutionary Psychology
on the internet
Science projects
There are plenty of great 8th grade science fair projects. You could play with something like air concepts for example.
what are the 3 varbles in fifth grade
Do nothing
there are lots of topics! you can find a few at science buddies.com there are lots more websites where you can find out!
what about UFO's
Yes