On heating gypsum at 373 k, it loses water molecules and becomes calcium sulphate hemihydrate. This substance is used to make toys, material for decoration and smooth surfaces. What is this substance commonly known as?

Correct option is C

The correct answer is (c) Plaster of Paris.

Explanation:
When gypsum (chemical formula: CaSO₄·2H₂O) is heated to around 373 K (100°C), it loses water molecules and transforms into calcium sulfate hemihydrate (CaSO₄·½H₂O). This substance is commonly known as Plaster of Paris, which is widely used in construction, decoration, and even for making toys and smooth surfaces.

Information Booster

Chemical Process:

• The process involves heating gypsum to 100°C, resulting in the release of water molecules and the formation of Plaster of Paris.

Key Properties of Plaster of Paris:

• Quick-setting: It hardens rapidly when mixed with water, making it useful for molding and casting.
• Uses: It is used in creating molds, casts, sculptures, and also in medical applications for making plaster casts for broken bones.

Historical and Cultural Significance:

• Ancient Egypt: Plaster of Paris was used by the Egyptians to make intricate decorative works and mummification masks.
• Modern Uses: Widely used in construction for making smooth wall surfaces and in the medical field for immobilizing fractured bones.

Additional Information:

• Cement: A construction material made by heating limestone with clay to form calcium silicate.
• Alabaster: A soft, translucent mineral, used for making sculptures and decorative objects.
• Clay: A natural material used in pottery, bricks, and tiles, which is not related to Plaster of Paris.