There are numerous different kinds of acidic substances, like battery acid, concentrated sulfuric acid and lemon juice. These substances all have their own values of acidity, however, which is measured using the pH scale.
The pH scale is a logarithmic scale designed to rank chemical substances along a spectrum based upon how acidic or non-acidic they are. Substances that rank lower than a seven on the 14-point scale are acidic. Pure water is ranked at seven, which is considered neutral. Above seven means the substance is a base, or alkaline, substance.
Battery acid is ranked as one of the most acidic substances because is has a pH value of zero. Concentrated sulfuric acid is also very acidic, being listed as one. Lemon juice and vinegar are also very acidic, but not as much so since they are ranked at a level two pH rating.
Some other acidic substances are orange juice and soda, which have a pH rating of three. Tomato juice and acid rain are also acidic substances, with a pH rating at four. Black coffee and urine are also considered acidic substances with pH ratings listed at five and six, respectively. There are also some substances with acidic pH ratings that may surprise people like bananas, which have a pH rating of five, or milk, which has a pH rating of six.