A substance is made of small brown particles and small white particles. When poured into water, the substance separates - the brown particles sink and the white particles float.
The original substance would be considered a(n) .

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume

i'm assuming that it's c.) red bank..