Some acids are very dangerous when they are concentrated (such as nitric, sulfuric and hydrochloric acid). But if they are diluted they cause less damage.
Organic acids are made from groups of atoms and their molecules mainly consist of hydrogen, carbon and oxygen atoms. The acidity of these acids comes from the hydrogen in the -COOH group of atoms.
Sulphuric, hydrochloric and nitric acids come from inorganic or mineral sources. The pure acids are all molecular. Sulphuric and nitric acids are liquids at room temperature. Hydrogen chloride is a gas which becomes hydrochloric acid when dissolved in water.
Acids are compounds that dissolve in water to give a solution with a pH less than 7. They form salts when they react with alkalis. They react with carbonates to form carbon dioxide. They give of hydrogen when they react with metals. All acids contain hydrogen in their formula and produce hydrogen ions when they dissolve in water.
Common alkalis are sodium hydroxide (NaOH), potassium hydroxide (KOH) and calcium hydroxide (Ca(OH)2). Alkalis are compounds that dissolve in water to give a pH higher than 7. They can be neutralized by acids to form a salt.
Some alkalis can do more damage to delicate tissues than acids. Caustic alkalis attack living tissue including skin.