Why oil doesn’t get salty when adding salt to potatoes while frying?

Question

I use to fry potatoes reusing the same (olive) oil several times (about 5-6 times), and I salt them while frying. But the the oil doesn’t get salty. What’s the reason for that?

In: 2000

Answer 1

The short and complicated answer is polarity.

The longer and more easily understood answer is magnets! A fundamental property of all molecules is polarity. Think of polarity as how “magnetic” a molecule is. Some molecules act as really strong magnets, like table salt, while others don’t act magnetic at all, like plastic. Every molecule falls on a spectrum between non-magnetic (non-polar) to extremely magnetic (polar). Molecules are like cliquey high schoolers in that they only want to hang out with other molecules who are the same as them: magnets with other magnets, and non-magnets with other non-magnets. The magnets and non-magnets wouldn’t stick together anyway as magnets only stick to other magnets (in this example anyway).

In the case of making fench fries, table salt is extremely magnetic while the cooking oil is completely non-magnetic so they don’t like to mix. Water on the other is a very magnetic so it is happy to hang out with the table salt all day.

Chemists take advantage of this magnetic (polar) property of molecules to do lots of fancy things in labs and industry but there are some real world examples that we deal with everyday besides cooking. If you were to splash your clothes with the hot oil while making those fries, it might be hard to get the stain out in the washing machine. As we have said, oil isn’t magnetic at all and water is, so they don’t like to mix. Soap is used as a intermediary between the two (soap molecules are giant with one side being non-magnetic and the other side very magnetic) but it isn’t a magic bullet as chemistry is complicated. So to get that stubborn stain out, you go to a dry cleaner. Dry cleaners use completely non-magnetic (non-polar) solvents (like tetrachloroethylene) instead of water to dissolve like minded non-magnetic (non-polar) stains from clothes, like the oil.

Hope this helps!