A key microscopic property that helps determine whether two substances will dissolve each other is polarity. When evaluating the interaction between a solute (the substance that is dissolved) and a solvent (the substance that does the dissolving), the polarity of the molecules plays a crucial role.
- Polarity relates to the distribution of electrical charge within the molecule. Polar substances (such as water) have significant differences in electronegativity between atoms, resulting in partial positive and negative charges. Nonpolar substances (such as oils or fats) do not have such charge separation.
The general rule of thumb is "like dissolves like":
- Polar solvents tend to dissolve polar solutes (e.g., salt dissolving in water).
- Nonpolar solvents tend to dissolve nonpolar solutes (e.g., oil dissolving in hexane).
Therefore, the polarity of the substances is a crucial microscopic property to consider when determining their solubility in each other.