Salts, Crystals and Their Uses in Daily Life


6.8  Salts, Crystals and Their Uses in Daily Life


Definition of salt
An ionic compound formed when the hydrogen ion, \(H^+\) from the acid, is replaced with the metal ion or the ammonium ion, \(NH_4\,^+\)


Physical properties of salts

  • Has flat surface, straight sides and sharp vertices
  • Has a fixed angle between two adjacent surfaces
  • Has a fixed geometrical shape such as cube, cuboid, rhombus and prism
  • Different crystals have different geometrical shapes
  • Same crystals of different sizes still have the same geometrical shapes
A crystal has specific properties because the particles in the crystal are arranged in a compact and orderly manner according to a specific design arrangement. 


Examples of salts and their uses

Salt Uses
Ammonium nitrate Fertiliser
Iron(II) sulphate Pesticide
Calcium sulphate Plaster of Paris- to support broken bones
Potassium manganate(VII) Antiseptic to treat wounds
Sodium chloride Food flavouring
Sodium bicarbonate Raising dough
Sodium benzoate Preserve chilli sauce
Sodium nitrate Preserve processed meat (sausage)