Silica is silicon dioxide (Sio2). It contains silicon and oxygen, but there are many types of silica (quartz, flint, sand). So how are these silica different from each other? Is is the arrangement of atoms?
Same for calcite (CaCO3). There are many - marbles, animal shells, bones. They have the same chemical formula, but are different from each other, how come?
Question about silica and calcite?
2011-06-18 9:37 am
回答 (2)
2011-06-18 10:14 am
✔ 最佳答案
Yes, these substances have different structures, which is derived from how they were formed. For example, carbon + lots of heat and pressure and time= diamonds, carbon + lots of pressure and time = coal.Sand & quartz + pressure and chemical changes = flint
Sand + heat = quartz
flint, quartz + erosion = sand
Animals + Ca and CO3 = Shells and bones
Shells and bones + erosion and pressure = limestone
limestone and shells + pressure, heat, chemical changes = marble
2011-06-18 6:34 pm
Silicon dioxide
Sand is a powder form of silicon dioxide while quartz is a crystalline solid. Their structure are roughly the same, i.e. both have giant covalent structure.(silicon and oxygen atoms covalently bonded throughout the structure)
Calcite
Animal shells and bones are not pure calcium carbonate so they are different.
Marble, limestone and chalk are three types of rocks that are mainly made up of calcium carbonate.
They are all ionic compound, however, the ions are bonded in different angles.
Limestone and chalk (sedimentary rocks) are formed by dead remains of marine organisms.
Under high pressures and temperatures, limestone recrystallize to form marble, which is a metamorphic rock.
Sand is a powder form of silicon dioxide while quartz is a crystalline solid. Their structure are roughly the same, i.e. both have giant covalent structure.(silicon and oxygen atoms covalently bonded throughout the structure)
Calcite
Animal shells and bones are not pure calcium carbonate so they are different.
Marble, limestone and chalk are three types of rocks that are mainly made up of calcium carbonate.
They are all ionic compound, however, the ions are bonded in different angles.
Limestone and chalk (sedimentary rocks) are formed by dead remains of marine organisms.
Under high pressures and temperatures, limestone recrystallize to form marble, which is a metamorphic rock.
參考: Chemistry Textbook
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