Answer:
NaCl dissolves into the water and dissociates into Na⁺ and Cl⁻ ions, present homogeneously throughout the solvent
SiO₂ settles down at the bottom of the vessel in the form of coarse particles
Explanation:
NaCl is a strong electrolyte that is, it dissociates readily in an aqueous solution. So when the water is added in the mixture, NaCl dissolves readily and is present uniformly in the solvent as Na⁺ and Cl⁻ ions.
SiO₂ has a strong ionic bond and is not dissociated by water, so it is present in the form of coarse particles at the bottom of the vessel.