How to tell if something is soluble in something else?

Understanding Chemical Solubility

When you are trying to figure out whether a substance will dissolve in a specific liquid, the golden rule of chemistry is simple: like dissolves like. This fundamental principle comes down to molecular polarity, which dictates how electrons are shared within a molecule.

Polar molecules, such as water, have a slight positive charge on one end and a slight negative charge on the other. Because of this charge imbalance, they are exceptionally good at breaking apart and dissolving other polar substances, as well as ionic compounds like table salt. The charged ends of the solvent attract the opposite charges of the solute, pulling the structure apart into solution.

On the other hand, nonpolar substances—like oils, fats, and many organic solvents—do not have these distinct positive or negative poles. Instead, their electrons are distributed much more evenly. Because they lack the electrical pull needed to interact with polar molecules, nonpolar substances prefer the company of other nonpolar substances. This is why oil will never mix into water, but it dissolves easily in another nonpolar liquid like turpentine.

To determine solubility quickly, look at the chemical structures of both your solute and your solvent. If both share similar polarity characteristics—either both polar or both nonpolar—you can generally expect them to mix successfully.