Gypsum is noted for absorbing heat due to its moisture content during heating.

• A. Gypsum
• B. Fiberglass
• C. Steel
• D. Concrete

Answer: (A)

Gypsum’s ability to absorb heat during heating comes from its water of hydration. Gypsum is calcium sulfate dihydrate, which contains chemically bound water. When gypsum is heated, it loses this bound water in stages (to calcium sulfate hemihydrate and then to anhydrous form). Dehydration is an endothermic process, meaning it absorbs a fair amount of heat as the water is driven off. That heat absorption helps slow temperature rise and adds fire-resistive effects in gypsum-containing materials.

Fiberglass doesn’t rely on bound water for heat absorption in the same way, so it isn’t noted for absorbing heat through dehydration. Steel conducts heat and doesn’t involve moisture-driven endothermic reactions. Concrete does contain moisture, but its heat absorption isn’t primarily due to dehydration of bound water like gypsum; its response is more about overall thermal mass and moisture transport, which isn’t the same feature highlighted here.