Sand is not soluble in water. When sand is mixed into water, the grains of sand will remain suspended in the water as long as they are being actively stirred and distributed through the liquid. When the water is left still, however, the particles of sand will settle to the bottom of the container holding the water, leaving plain water above the layer of sand. This type of mixture is called a suspension, because the sand was suspended in the water.
Salt is soluble in water. When added to water, salt dissolves so that there are no longer separate salt crystals in the liquid. When the water and salt combination is left undisturbed, the salt remains dissolved throughout the liquid.
sand is insoluble in water. The mixture of sand and water is a heterogenous mixture.