I'll start by establishing my potentially flawed understanding of solutions:

A solution is a completely homogenous mixture. That means that the two (or more) substances are evenly distributed throughout the mixture (or the cross-section of the mixture in question), and that this distribution is happening on an atomic/ionic or molecular level. One can get a pretty even distribution of the components in a mixture if one swirls it nicely, but it will never be homogenous unless they are mixing at the smallest level, and therefore not a solution.

For solids dissolved into a liquid, the solid must be a salt, so that the ions it is composed of can break a part and connect to the water molecules (for example). As such, for a solid to be dissolved into a liquid, that liquid must also be polar, like water.

When talking about solutions made of fluids (gases and liquids), the molecules or salts doesn't have to break apart. They can remain whole, because the homogenous distribution will occur anyways. This is because of the diffusivity of fluids; entropy will distribute the molecules/salts evenly, and as such, this distribution isn't happening on an atomic level. (Perhaps the distribution does happen on an atomic level if the liquids are made of salts, not sure).

Okay, now that my understand, or lack thereof, has been established, here's the question:

If two nonpolar or two polar liquids are mixed together respectively, will the mixture always be a solution, because of fluid dynamics evenly dispersing the molecules, without any deconstruction of the molecules?

  • 3
    $\begingroup$ Ever heard of sugar? Is it a salt? $\endgroup$ – Ivan Neretin Oct 22 '20 at 10:35
  • $\begingroup$ @IvanNeretin Hmm, I see. We have only been taught about solutions in the context of salts in class. It seemed like it needed to be a salt for a solution to occur. $\endgroup$ – A. Kvåle Oct 22 '20 at 10:46
  • 4
    $\begingroup$ I know, chemistry is commonly taught in a way that suggests it is completely detached from everyday life. Well, in fact it isn't. $\endgroup$ – Ivan Neretin Oct 22 '20 at 11:07
  • 1
    $\begingroup$ There is no sharp boundary between being polar and nonpolar, so it depends on the quantitative properties like permitivity, dipole moment, ability to form hydrogen bounds or donor-acceptor bonds. Additionally, liquids may mutually react, releasing producs not soluble in them. $\endgroup$ – Poutnik Oct 22 '20 at 11:12
  • 2
    $\begingroup$ "If two nonpolar or two polar liquids are mixed together respectively, will the mixture always be a solution?" The qualifier of "always" means he answer is NO! There are oil, [non-polar liquids] when mixed do not form a solution. $\endgroup$ – Hal Oct 22 '20 at 16:14

It has already been pointed out that your text is incorrect. Saccharose (commonly known as sugar) is not an ionic compound yet it dissolves very well in water. It is not alone although I am too lazy to think up a non-carbohydrate example.

I’ll also point out that ionic compounds exist that are insoluble or poorly soluble in water, although some may rightly argue that their bonds tend to be more covalent than ionic.

As for two different liquids mixed together, the answer is: You can’t say a priori. (Or, in a highly logical reading of your question: no, the result will not always be a solution.) Many polar liquids will form a solution with many other polar liquids but in some cases the pairing will not. Conversely, a polar liquid such as ethyl acetate or acetone can form a solution with a practically unpolar liquid such as hexane.

  • 1
    $\begingroup$ Can you explain (or point to the explanation) why ethyl acetate forms a solution w/ non-polar hexane? $\endgroup$ – Stanislav Bashkyrtsev Oct 30 '20 at 8:31
  • $\begingroup$ @StanislavBashkyrtsev I cannot. I can run the experiment and see the result but I cannot tell you any underlying calculatory reasons. $\endgroup$ – Jan Nov 18 '20 at 6:55

Not the answer you're looking for? Browse other questions tagged or ask your own question.