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When two liquids mix, and they are not hindered by a polarity mismatch (like oil and water), why don't they always form a homogenous mixture? Due to entropy, a liquid will disperse itself evenly. This even distribution will lead to homogeneity, no? According to an answer to this question (one given when this question looked different), said that they don't always distribute themselves evenly. So, let me lay done some ground rules:

  • Both the liquids are non-polar or polar
  • The liquids do not react in a way that creates products

Now, what hinders these liquids from dispersing evenly in each other?

Also, I'm going to clarify a certain conception I have, in case it is wrong:

A homogenous mixture is a mixture where the parts are evenly distributed. A solution is a homogenous mixture, where the solute has been deconstructed into its ionic components.

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    $\begingroup$ 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
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    $\begingroup$ 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
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    $\begingroup$ 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
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    $\begingroup$ "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
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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.

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    $\begingroup$ 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

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