Why do the liquids in the “density column” experiment not mix?
You are supposed to choose immiscible liquids: that is, no two of the liquids are able to mix with each other. If this is not possible, at least choose them so that no two adjacent liquids will mix. Of course the liquids will not “repel”; in a density column the only way for that to happen would be by defying gravity. If you want to know why some pairs of liquids will not mix, you will have to learn about intermolecular forces and the kinetic molecular theory; further analysis requires a good deal of thermodynamics also. In a nutshell, consider water and oil. Water molecules attract each other more strongly than they attract oil molecules. Therefore, all the water molecules stay together and do not mix with the oil. According to Wikipedia you can actually find 8 liquids no two of which mix with each other. In order from top to bottom in the density column: paraffin oil, silicone oil, water, aniline, perfluoro(dimethylcyclohexane), white phosphorus, gallium, mercury. It is worth noting
