Understanding "Like Dissolves Like"
The key principle here is that "like dissolves like". This means:
* Polar substances dissolve best in polar solvents.
* Nonpolar substances dissolve best in nonpolar solvents.
Polar vs. Nonpolar
* Polar molecules have an uneven distribution of electrons, creating a positive and negative end (like a magnet). Think of water (H₂O) – the oxygen side is slightly negative, and the hydrogen side is slightly positive.
* Nonpolar molecules have an even distribution of electrons and no distinct positive or negative ends. Think of oils and fats.
Rubbing Alcohol (Isopropyl Alcohol)
Rubbing alcohol is polar because the oxygen atom is more electronegative than the carbon and hydrogen atoms. This creates a slight negative charge around the oxygen and a slight positive charge around the rest of the molecule.
Why Rubbing Alcohol Works
Since rubbing alcohol is polar, it can form hydrogen bonds with other polar substances like water. This allows it to dissolve many polar substances, such as:
* Other alcohols
* Sugars
* Some salts
Nonpolar Solvents
To dissolve nonpolar substances like oils and fats, you need a nonpolar solvent like:
* Hexane
* Diethyl ether
* Toluene
Key Takeaway
While rubbing alcohol can dissolve some nonpolar substances to a limited extent, it is primarily a good solvent for polar substances.
