I've got it!
It seems to me the OP is going with the carb cutaway project, but a theory needs to be tested right? So how can they test gasoline vs. ethanol ("renewable" fuels) to see which is more efficient?
Theory: ethanol fuel contains less BTU's than gasoline by volume.
Test: show both fuels burning on a wick heating a metal bowl of water, with a thermometer in the water. The cutaway carb could be part of the display, along with an ear of corn, and a soup can painted like a barrel of crude oil.
1. Flame is like flashing lights, and will get lots of attention.
1. You would need to show the flow rate was the same for both fuels. Maybe Mom can come up with intravenous drip stuff for this part?
2. Would the school allow flame? If the answer is no, this whole idea is shot.