According to the FAQ page:
Does the entry need to be based on the science of chemistry?
No, it is encouraged for entries to explore any field of science or multiple fields.
I suggest, if I may, that you also include physics (mechanics, electronics, or what have you). For electronics please review the following articles since they are simple to build and all based on a basic 555 timer circuit:
http://www.science20.com/square_root_not/snap_circuits_science_hot_liqui... http://www.science20.com/square_root_not/snap_circuits_science_cable_tes... http://www.science20.com/square_root_not/snap_circuits_science_create_ca... http://www.science20.com/square_root_not/snap_circuits_science_pencil_an... http://www.science20.com/square_root_not/snap_circuits_science_magnetic_...
I hope to be able to post up some more 555 circuits that explain other electronic components such as the transistor before the deadline.
One construction toy that you can include in the kit is K’nex. I often see K’nex sets at second-hand stores like Goodwill or Salvation Army so I decided to see if K’nex can be co-opted for science. The following set of photographs is a test tube rack that I built out of K’nex:
The upright K’nex rods support the structure and serve as test tube drying pegs.
You might also want to include some extra K’nex parts to Model DNA