10 g Boric acid + methanol + a couple drops of concentrated sulfuric acid in a water cooler jug… Swirled around to produce flammable boric acid trimethyl ester, B(H3CO)3. Drop a burning splint and rapid combustion + a loud whoosh noise is what you get :) It’s green because boron compounds burn with a green flame.
Here is the production of the ester:
B(OH)3 + 3 CH3OH —> B(H3CO)3 + 3 H2O
Boric acid + methanol —> boric acid trimethyl ester + water
The reason for adding concentrated sulfuric acid is to shift the equilibrium to the right toward the ester because sulfuric acid is very hygroscopic (moisture absorbing) and it removes water from the system.