When the scale gets small enough, chemistry is also physics
You could say that on a "bulk" scale, similar stuff mixes more easily. For example, oil does not mix easily with water, but other compounds consisting of small polar molecules (e.g. light alcohols)
do mix easily with water .
Salts dissolve easily in water, but not in oil.
But on a small scale, i.e. molecule to molecule, or
part of molecule to
part of another molecule, opposites do attract each other. For example, the oxygen in water holds a small negative charge, the hydrogen atoms hold a small positive charge. This causes a slight attraction between the hydrogen atoms in one molecule and the oxygen in another, creating an attraction between the molecules. Mind you, this attraction (so called hydrogen bond) is much weaker than the internal bonds in the water molecule. They form and break many times every second.