Final answer:
The principle 'like dissolves like' dictates that polar substances dissolve in polar solvents, and nonpolar substances dissolve in nonpolar solvents, based on their intermolecular interactions.
Step-by-step explanation:
The principle that explains why substances dissolve better in solvents of similar polarity is known as like dissolves like. This means that polar substances, which have uneven distribution of electron density and may have positive and negative ends (poles), are more likely to dissolve in other polar substances. This is due to their ability to engage in intermolecular interactions such as hydrogen bonding or dipole-dipole attractions. Conversely, nonpolar substances with even distribution of electron density dissolve better in nonpolar solvents because of the induced temporary dipoles resulting in London dispersion forces. For example, sodium chloride (NaCl), a polar compound due to its ionic nature, readily dissolves in water, a polar solvent, but not in oil, which is nonpolar. Similarly, nonpolar wax dissolves in nonpolar hexane, but not in polar water.