Aivsta

Does anyone know how Leonardo Da Vinci used the scientific method? I was readying an article and it concluded with this question. I would realy like to know. And if possible, if you could provide some evidence how.

substances like water and salt, or kool-aid and water, or makeing coffee.

can somone tell me if i mixing two substances is a chemical change. If so please state why, and if not please state why as well. P.S please answer asap.