Plaster of Paris, used by doctors to set broken bones, is made by heating

Explanation

1. 01

   Gypsum is calcium sulphate dihydrate, CaSO₄·2H₂O.

2. 02

   Heating it to about 373 K drives off some water and gives plaster of Paris, CaSO₄·½H₂O, which sets hard again when mixed with water.