Ceramics
Chemistry: Cambridge International A Level, topic 2.1.4
Ceramics & Giant Covalent Structures
Ceramics are giant covalent structures and include magnesium oxide, aluminium oxide and silicon dioxide.
No specific formula
- Giant covalent structures don't have a specific formula because the structure can be any size.
- In theory, they can continue forever - a diamond may have 50,000 or 1,000,000,000 carbon atoms.
Very high melting points
- The strong covalent bonds between atoms make them solids at room temperature.
- High temperatures and significant energy are required to break the structure's covalent bonds.
1 large molecule
- Giant covalent structures exist as 1 large structure or molecule.
- There are no intermolecular forces because there is only 1 molecule.
Silicon Dioxide (Silica) & Uses of Ceramics
Silicon dioxide (silica) is a giant covalent structure. Silica's empirical formula is SiO2. The properties of silica and other ceramics like magnesium oxide & aluminium oxide give them many uses.
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Covalent bonds
- In silica, each silicon atom is covalently bonded to 4 oxygen atoms.
- The oxygen atoms bridge between two silicon atoms to build up a giant-covalent structure.
- Magnesium oxide (MgO) & aluminium oxide (Al2O3 also contain multiple strong covalent bonds.
Hard
- Like diamond, there are lots of strong covalent bonds in ceramics. This makes them very hard.
Insulator
- Silica and other ceramics are good electrical insulators. This is because they have no free electrons.
High melting point
- A lot of energy is needed to break strong covalent bonds.
- Ceramics have lots of strong covalent bonds. This means that it has a high melting point.
Uses of ceramics
- Silica dioxide is used to line furnaces due to its high melting point.
- Aluminium oxide is used in hip joints. It is very strong, so resistant to wear. It is also relatively light.
- Magnesium oxide is also used to line furnaces. It is also used in cooking equipment as the heat producer because it is a good electrical insulator.
- Electrical currents are used to produce heat in cooking elements. It is beneficial for heating elements to be electrical insulators for safety reasons.
Test yourself on Ceramics
Which of these are properties of silica?
What is the empirical formula for silica?