Acids Acids are substances that release hydrogen when they are dissolved in water. Acid is also a common word in everyday use, but it has a precise definition in chemistry.
Acids are also the opposite of bases.
Acids are usually mentioned with bases, because they are sort of similar. Acids have a sour taste and can sting the skin. People use acid too, they make ink and cleaning substances to shine cars. A type of acid is citric acid. It is found in some fruits, like lemons.