Cambridge IGCSE Chemistry · Syllabus 0620 · Acids, Bases and Salts
Base
What is Base?
An oxide or a hydroxide of a metal. A base reacts with an acid to give a salt and water, and with an ammonium salt to give a salt, water and ammonia. A base does not have to dissolve in water.
This definition is part of the Acids, Bases and Salts chapter in Cambridge IGCSE Chemistry.
Common mistakes with Base
- “A base is the same thing as an alkali.” Repair A base is an oxide or a hydroxide of a metal. An alkali is a base that dissolves in water. Copper(II) oxide is a base — it neutralises acids — but it is insoluble, so it is not an alkali and no solution of it exists to turn litmus blue.
- “Amphoteric means neutral — it sits in the middle.” Repair The opposite. An amphoteric oxide reacts with both acids and bases to give a salt and water. A neutral oxide reacts with neither. Aluminium oxide and zinc oxide are the two you need; they are defined by evidence of reaction, never by position on a table.