Falling Sand
This is a playful simulation, not a chemistry model. Pick a material, then draw in the box. Sand falls, water flows, fire burns what it can, and wind pushes things around. A spout copies whatever it touches and keeps making more.
Draw with the mouse or a finger. The page still scrolls outside the box. Number keys 1 through 0 pick materials.
Clear the sandbox?
Simulation adapted from dust by Max Bittker, ISC License. Fluid code by Oliver Hunt, MIT License. Colors by husl, MIT License. License notes