Pure water is neutral, with a pH of 7.0. When chemicals are mixed with water, the mixture can become either acidic or basic. Vinegar and lemon juice are acidic substances, while laundry detergents and ammonia are basic. These chemicals can cause severe burns. Automobile battery acid is an acidic chemical that is reactive.
Automobile batteries contain a stronger form of some of the same acid that is in acid rain.
Household drain cleaners often contain lye, a very alkaline chemical that is reactive.