A material can dissolve and remain present even when its grains cannot be seen. Other grains can stay visible and settle. Follow each material separately: an ordinary sand-catching filter holds sand grains, but dissolved sugar passes with the water. These are paper records, not instructions to mix, taste or heat anything.
Worked example
In a different paper record, salt dissolves in one cup while sand stays visible in another. An ordinary filter catches the sand, not the dissolved salt. The salt is still in the water that passes through. Being out of sight is not the same as being removed.
Two Paper Cup Records
Cup L contains water and a little sugar. After stirring, no sugar grains are visible. Cup M contains water, a little sugar and sand. Its sugar dissolves, but visible sand grains settle. An ordinary filter traps the sand grains from M while its water and dissolved sugar pass into a new cup. Neither cup is heated. Do not taste any mixture; these are imagined observations, not drinking-water tests.