Question

what is the action of heat on gypsum?

Answer 1

On heating gypsum at 373 K, it loseswater molecules and becomes calcium sulphate hemihydrate ( CaSO4. 1/2 H2O).
This is called Plaster of Paris. ‎CaSO4·2H2O → △ CaSO4.

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Answer 2

While heating gypsum at 373K, it will lose water molecules and converted into plaster of Paris.
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