Final answer:
Anything insoluble in water stays on the filter paper and does not pass through. Filtration allows water to pass while trapping insoluble substances like sand or certain ions like CO32- and PO4³- due to the size difference or polarity.
Step-by-step explanation:
Anything that is insoluble in water will remain on the filter paper & will not pass through it. This concept relates to the process of filtration, where a mixture of a liquid and a solid can be separated based on the size of the solid particles. For instance, when sand, which is insoluble in water, is mixed with it, the result is a heterogeneous mixture. During filtration, the water passes through the filter paper while the sand, being larger in size and not dissolved, remains on the filter paper. This process occurs because filtration physically separates the mixture without changing the chemical makeup of the substances involved.
Contrast this with a true solution, such as a sugar-water mixture, where the sugar dissolves completely and forms a stable, homogeneous mixture. In a true solution, the dissolved particles, which are very small—typically less than 1 nm in diameter—pass through the filter along with the water. Hence, substances that are nonpolar or certain compounds like those of carbonate (CO32-) and phosphate (PO4³-) that are generally insoluble in water would similarly remain on the filter during filtration.