What chemical reactions can you make in the falling sand game

Any. I'm not a chemist but you can model the entire periodic table and the interactions between elements Oxygen and Hydrogen can make Water, Uranium emit a ratiation sand that can cause other "sands" to... whatever you want. So anyway, long story short, you can model reality or just make up your own reality. Note that all of this kind of stuff takes time to script. Nothing is automatic.