Acids are made up of at least one hydrogen atom. Some examples of acid include inorganic substances known as mineral acids, which are sulfuric, nitric, hydrochloric and phosphoric acids. Acid is also made up of organic compounds belonging to the carboxylic acid, sulfonic acid and phenol groups.
According to Encyclopedia Britannica, factors that identify an acid are a substance tasting sour in a water solution or changing the color of certain indicators, such as turning blue litmus paper red. Some substances that are acids, such as iron, react with metals to liberate hyrdrogen, react with bases to form salts or promote chemical reactions called acid catalysis.