Re: Can oil and water mix

Andrew,

First, the oxygen atom of a water molecule has a partial negative charge and the hydrogens each have a partial positive charge. Thus the overall molecule is polar, which is just another way of saying that there is one area of predominantly positive charge and another area (usually as far away from the first area as possible) of predominantly negative charge. This separation of charge affects where other molecules will react with the first.

Second, oil and water certainly can "mix," but they never form a homogeneous solution like salt or sugar in water (I have chosen two solids as examples of solutes, but liquids can be solutes as well). A solution consists of the solute (the substance that dissolves) and the solvent (the substance in which the solute dissolves). The molecules of the solute are even distributed among the molecules of the solvent, and this even distribution at the molecular level is the key characteristic when thinking about oil and water. When oil and water mix, they form pockets or bubbles of only-water or only-oil; it is never the case that water and oil molecules are evenly distributed. Although at the surfaces of these bubbles you have molecules of water next to molecules of oil, the vast majority of oil molecules are surrounded by other oil molecules and the vast majority of water molecules are surrounded by other water molecules. This property of two liquids not being able to form a solution is called "immiscibility." You can crudely mix oil and water by agitating the mixtures and breaking up all of the big bubbles into little bubbles which spread out from each other and look like a solution, but if your eyes see objects this small you would in fact see just pockets of only-oil and pockets of only-water.

I hope this answers your question. Please contact me directly if you still have some confusion regarding this issue.

Chris Larson