What is gypsum primarily composed of?

Gypsum is primarily composed of calcium sulfate dihydrate, which is a chemical compound with the formula CaSO4·2H2O. This means that gypsum consists of calcium sulfate along with two water molecules. The presence of water in the dihydrate form is essential for its unique physical properties, such as its ability to form a soft, chalky mineral that is used in various construction and building materials, including drywall and plaster.

Understanding gypsum's composition is crucial in fire safety, particularly in the context of its use as a building material. Gypsum has inherent fire-resistant properties because it can release water vapor when heated, which helps to slow down the spread of fire. This makes it a popular choice in fire-rated wall assemblies, ceilings, and other fire-prevention applications.

The other options do not accurately describe the composition of gypsum. For example, silicon dioxide is found in materials like sand and quartz, while calcium carbonate and sulfuric acid do not form gypsum. Magnesium sulfate, on the other hand, is a different hydrated salt and is not relevant to gypsum's chemical makeup. Thus, the correct characterization of gypsum as being primarily composed of calcium sulfate and water molecules aligns with its physical and chemical properties crucial for fire safety applications.