Why don't polar molecules and nonpolar molecules mix?

Solution:

By the following ways the polar molecule doesn't mix with non-polar molecule

Polar molecules have a portion of their molecule which, relative to the rest of the molecule, is more negative.

Water, for example, has a bent, or V-shape, due to the 2 lone electron pairs on oxygen. This makes the oxygen end more negative than the hydrogen end. This negative area allows for hydrogen bonding between that molecule and other molecules which are also polar.

Non-polar molecules don't have a portion of the molecule which is more negative than the rest. An example of this is a hydrocarbon, like butane. Because there is no relatively negative region to the molecule, it cannot partake in hydrogen bonding and therefore does not mix with polar molecules.

Thus we can conclude that Polar mixes with polar; non-polar mixes with non-polar.