If Gypsum () is heated strongly to temperatures exceeding (e.g., ), it forms a product known as "dea — s Block Elements Chemistry Question

💡 Solution & Explanation

Heating above $393\text{ K}$ drives off all the water of crystallization, leaving completely anhydrous Calcium Sulphate ($CaSO_4$). It is called "dead" because it permanently loses its ability to form a plastic mass and set hard when mixed with water.