Acid

An acid has a <a href="PH">pH</a> value lower than 7. It is a substance that will react with <a href="Water">water</a> to produce H₃O⁺ and with a <a href="Base">base</a> to neutralize to <a href="Water">H₂O</a> and a salt. On a universal indicator, strong acids show up as a red or dark orange colour and weaker acids show up as an orange or yellow colour.

Brønsted Lowry Acid

A <a href="Molecule">molecule</a> that donates <a href="Proton">H^+.</a>

Lewis Acid

A <a href="Molecule">molecule</a> that can accept a pair of <a href="Electron">electrons</a>.

Structure - ends with -COOH

Hydrochloric acid

HCl

H⁺ Cl^-