Acid

An acid has a pH value lower than 7. It is a substance that will react with water to produce H₃O⁺ and with a base to neutralize to water 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.

Acid can  cause serious damage to human health. The correct PPE (Personal Protective Equipment) should be worn when working with acids.

Also see alkali.

Brønsted Lowry Acid

A molecule that donates a proton.

Lewis Acid

A Molecule that can accept a pair of electrons.

Structure - ends with -COOH

Hydrochloric acid

HCl

H⁺ Cl^-