Which of the following are insoluble in water?
The solubility of a substance is influenced by the specific compound, temperature and pressure. Some substances completely mix in water, such as ethanol, while other substances do not such as sand.
Oil does not mix with water because it is nonpolar and hence, does not interact well with the water molecules and floats at the top of water. Likewise sand is insoluble in water since water is not strong enough to dissolve sand.