Question

what is dead burnt pop

Answer 1

Yo!

Here's your answer!

When plaster of Paris (CaSO4.1/2 H2O) is heated above 393 K, its water of crystallisation is lost and anhydrous Calcium sulphate is left that is known as a dead burnt plaster.

Hope that this helps you!

-TGA

Answer 2

Plaster of Paris is prepared by heating gypsum at 120° C.
2CaSO4.2H2O → (CaSO4)2.H2O + 3H2O 
  Gypsum        Plaster of Paris   

On heating plaster of Paris at 200°C, it forms anhydrous calcium sulphate, i.e., dead plaster which has no setting property as it absorbs water very slowly.