Question

in the preparation of plaster of Paris temperature plays an important role why

Answer 1

because if gypsum is heated beyond the temperature 373 K then all the water of crystallization is removed from it which results in anhydrous calcium sulphate which is also called as dead burnt plaster. The disadvantage of this dead burnt plaster is that it doesn’t set like plaster of Paris after adding in water.

Answer 2

it is obtained when gypsum is heated to 393 K

above 393K , no water of crystallisation is left and anhydrous calcium slphate CaSO4 is formed. Hence it is known as 'dead burnt plaster'.

this is the reason why temperature plays an important role in preparation of plaster of paris  

hope it is useful