Store bought rubbing alcohol contains a large percentage of water and can easily be diluted further. Rubbing alcohol typically consists of 70 percent isopropyl alcohol and 30 percent water. Higher concentrations of isopropyl alcohol are generally not referred to as rubbing alcohol.
Isopropyl alcohol easily dissolves in water for two reasons. First, isopropyl alcohol contains a short hydrocarbon chain. Second, the hydroxyl group present forms hydrogen bonds with water molecules. When adding water to rubbing alcohol for cleaning purposes, tap water should be avoided because the minerals present can cause streaks. Distilled water should be used, as it does not contain added minerals.