Matter is the basic unit of all things in the world, whether living or nonliving. It is not only useful in chemistry, but also to other fields of science like physics. Physics deals with motion, so it has something to do with matte especially the movement of molecules for solids and fluids.
Because its in group one....which only lose or gain electrons.....thus it will only have oneelectron to fulfill its octect rule
So basically, the change in color effects the amount of cations in the solution making it a physical change rather than a chemical one, defying the law of conservation of mass! I hope this helped! (The only time the change in color affects the amount of cations is in the Alkaline Earth Metals)
source: college science teacher