The correct answer is option 4. Calcium carbonate.
Limestone, chalk, and marble are all different forms of calcium carbonate (CaCO₃), a chemical compound composed of calcium, carbon, and oxygen. Let's briefly discuss each of these forms:
1. Limestone: Limestone is a sedimentary rock primarily composed of calcium carbonate. It often contains fossilized remains of marine organisms. Limestone is a versatile material and is used in various industries, including construction, as a building material, and in agriculture to neutralize acidic soils.
2. Chalk: Chalk is a soft, white, porous form of limestone. It is composed mainly of microscopic marine organisms, such as plankton, that have accumulated over time. Chalk has been historically used as a writing tool (chalk sticks) and is also used in classrooms for writing on blackboards.
3. Marble: Marble is a metamorphic rock formed from the recrystallization of limestone under high pressure and temperature. It has a distinctive, often polished appearance and is used in sculpture and architecture for its aesthetic qualities. Marble is also composed mainly of calcium carbonate.
All three forms share the common chemical composition of calcium carbonate, but their geological processes of formation and physical characteristics differ. The presence of calcium carbonate makes them susceptible to chemical reactions, such as the reaction with acids, where carbon dioxide is produced, leading to phenomena like effervescence. |
