[dameon2008]

Alright, so im supposed to be makeing a project for my art class in collage, and im trying to think outside the box... Were supposed to make a self portrait that is also an island, and that floats for 3 hrs. i had a few ideas bumping around my head and then i came up with one thats guarenteed to turn heads. i want a structure that will innitially sink, but within will have a chemical reaction that will cause it to produce gas and slowly (or quickly) rise to the surface.

My problem lies in the chemical reaction that would be ideal for this.
the ones i had been thinking on were as follows

Use dry ice, the gas produced as the dry ice changes could potentially raise structure to the surface

Use MnO₂(from d-cell batteries, i think durecell) and Hydrogen peroxide which SHOULD produce O₂    My apprehension at this one is the fact that there is a heat issue with this reaction(i think) and also i dont know if it would be hazordus to a lake or not.

If anyone else can give suggestions for a supurb way to make a sinking structure float that is non-harmful to water or animals i would be extreamly pleased.

[nj_bartel]

sodium bicarbonate and acetic acid?

[Borek]

I would think about some other acid - citric for example. Use solid acid in crystallic form, so that the reaction doesn't start before wetting mixture.