Acid

On a PH scale that ranges from 0 to 14 acid falls between 0 and 7.
The properties of acid are:
- reacts with most metals to form hydrogen gas
- tastes sour like lemons
- frequently feels sticky
- usually gases or liquids

Some examples of acids are soda, vinegar, battery acid, orange juice, tomato juice, urine, acid rain, saliva, and grapefruit.

(Vinegar is one of the many example of acid. It is a 2 on the PH scale http://staff.jccc.net/pdecell/chemistry/phscale.html)