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Like dissolves like
This topic is intended to follow Solutions and Talking solutions and looks at how liquid solvents and different solutes form liquid solutions. It would also help if you were familiar with the topic From atoms to molecules.
In the FAQ section of Talking solutions the following question and answer was put forward:
all solvents dissolve all solutes?
The rule of thumb is that "like dissolves like". Polar/ionic solvents dissolve polar/ionic solutes and non-polar solvents dissolve non-polar solutes. For example, water is a polar solvent and it will dissolve salts and other polar molecules, but not non-polar molecules like oil. Petrol is a non-polar solvent and will dissolve oil, but will not mix with water.
The rule mentioned above, "like dissolves like", is a very handy way of determining which substances can be dissolved in which solvents.
Types of substances that form solutes
Metals are generally not very soluble in the common solvents but non-metals, molecular compounds and ionic compounds are all soluble in at least one common solvent. Liquid solvents are normally either polar or non-polar but, at high temperatures, liquid salts and metals can act as solvents. We will limit ourselves to polar or non-polar solvents, marked in red in the above table, as they are the most common solvents.
Polar molecules are aggressively attracted to other polar molecules, or even free ions, and form strong bonds between themselves. They feel little attraction to non-polar molecules and tend to ignore them in their rush to find other polar molecules or ions.
Non-polar molecules tend to group together, because they are pushed out of the way by polar molecules, forming weak bonds between themselves. In this way, polar molecules aggressively seek each other out, excluding non-polar molecules from mixing with them and forming a solution. While non-polar molecules form much weaker attractions for each other, they will mix and form solutions. Like dissolves like!