Why do vinegar and oil not mix?

Question

chemistry

Answer 1

This has to do with a thing called the hydrophobic effect.  Many try to understand this phenomenon but at a really deep level, I don't think anyone does.  

In simple terms, the hydrophobic effect says that like dissolves like.

Greasy, oily things like to be with other greasy, oily things.  The thing that greasy things have in common is that they are nonpolar, that is, they have no charge and their electrons are pretty evenly spread around.  This happens with oil because it has hydrogen hooked to carbon which isn't strong enough to hold more than its share of electrons.

On the other hand, things like salt and water either have a charge or are really polar meaning that 1 atom holds onto the electrons more tightly that another atom so both atoms have a partial charge.  This is what happens with water, which vinegar is composed mostly of.  The oxygen holds most of the electrons from both of the hydrogens so they have a partial charge.  This means that salt can dissolve (it has a charge) but oil cannot.

This is a really important question because these hydrophobic forces hold the proteins in your body together.  These proteins facilitate every chemical process you use to think, breathe, smell, taste or see.  When a drug interacts with a protein, it usually goes to one of the greasy areas inside the protein to do its work.

The person who can really solve the math behind this (and no, you wannabe physics geeks, increasing the freedom of the water molecules is NOT the solution) may well win something more that a few points on Yahoo.  They may win the Nobel Prize.

Answer 2

Oil is made of hydrophobic (water-hating) carbon chains. Vinegar is acetic acid which is made of hydrophilic (water-loving) groups.

Answer 3

Vinegar is 95% water and has a slightly higher density.

And, water, as you know will not mix with oil.

Water is a 'Polar' substance while Oil is not.

"Like dissolves Like".

Answer 4

oil is less dense than vinegar, so it floats on the top.  just like a piece of foam would float on water.