Final answer:
Mixing soil and sand with water will lead to a suspension where the soil settles to the bottom and sand is mixed within or on top, depending on its size. The water, unable to dissolve these large particles, passes through, separating from the solid materials when allowed to stand or filtered.
Step-by-step explanation:
When you mix soil and sand together and then add water, you create a heterogeneous mixture known as a suspension. In such a mixture, the components are not evenly distributed, and they will not stay mixed indefinitely. If you let this mixture sit, you'll see that the heavier particles, predominantly composed of soil, will settle at the bottom due to gravity, and the sand may be found on top or mixed within the soil, depending on their relative sizes and densities. This is because neither soil nor sand dissolves in water; they are both too large to form a solution with water.
The process is similar to filtering a mixture; pouring it through a filter would allow the water to pass through while leaving the solid particles of sand and soil behind. This phenomenon demonstrates the differing properties of soil and sand textures, where clay soils have many small spaces that can hold water, and sandy soils have larger spaces but fewer of them.
Sand and soil do not affect the water's ability to be a compound of hydrogen and oxygen, and the oxygen within it remains an element, not altered by the presence of sand and soil. Therefore, the correct answer to the student's question is Option D: The water will pass through the mixture, leaving soil and sand separated.