If you mix rubbing alcohol and water, you'll find that the liquid separates into two layers. You can use a combination of salt and food coloring to easily separate the alcohol from the water.

A salt solution has a property that makes it easy to separate liquids: The molecules in water are more polar than those in alcohol, so salt ions can bond with them easier. So, when you add salt to a solution of rubbing alcohol and water, the alcohol molecules will separate from the water, and the water will wind up at the bottom.

This separation technique, called azeotropic distillation, works best when the alcohol and water have a difference in boiling points. For example, alcohol boils at 78 degrees Celsius while water boils at 100 degrees.

Distillation is the process of heating a liquid so volatile compounds boil off to create vapors. These vapors can then be collected, used to make alcohol or purify the original liquid.

The problem is that alcohol and water bind to each other, forming an azeotrope (a state of temperature and pressure where the two substances have a low or high boiling point). This means that distillation cannot fully separate the two components.