this post was submitted on 30 May 2025
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They do, you just didn't wait long enough. If the densities are different enough, sugar-water solutions can stay separated for weeks or even years. Given enough time though, they would eventually form a uniform solution.
How can they stay separated for so long?
For the same reason that saltwater can remain separate from fresh water, or even hot water and cold water - diffusion is typically a slow process, particularly if you do not stir, or otherwise mix the substances.
Consider this: drop a single drop of food dye into a glass of water. There's no way the entire glass immediately turns into the relevant colour, it takes time for the molecules to move about.