|MadSci Network: Chemistry|
A solution is an intimate mixture of one substance, whatever its state, with a liquid. So indeed a liquid can dissolve in a liquid or a gas can dissolve in a liquid.
The prime requirement is that the forces between the two substances in the mixture are "better" energetically than in the separate substances, so you also have to take into account the changes in entropy or disorder and the overall change in Gibb's Free Energy on making the solution.
My favourite solution of a liquid in a liquid is alcohol in water - miscible in all proportions!
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