Theory:

Calcium sulphate hemihydrate is commonly known as plaster of Paris. The name is derived from the place of its origin Montmartre in the Paris district. The chemical formula is CaSO412H2O.
Preparation of plaster of Paris:
  
When gypsum (CaSO42H2O), is heated in a rotating kiln at \(300\)°F, it loses its water molecule and forms calcium sulphate hemihydrateCaSO412H2O.
 
Properties of plaster of Paris:
  • It is a white powder.
  • It acts as an oxidizing agent under extreme conditions.
  • It produces gypsum when mixed with water.
Uses of Plaster of Paris:
 
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Uses of plaster of Paris
  • It is used in making casts for statue, dentistry, surgical instruments, and toys etc
  • It is used in construction for making smooth walls, and in the creation of walls and ceilings  designs.
  • It is used in making chalks and also helps in setting fractured bones during surgery.
  • In laboratories, it is used to seal air gaps in the apparatus.