AS-Level Chemistry Chapter 5 States of Matter Ceramics

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Ceramics

1) A ceramic is an inorganic non-metallic solid which is prepared by heating a substance or mixture of substances to a high temperature.

2) Ceramics often contain silicon dioxide, magnesium oxide and aluminium oxide. This gives ceramics their giant covalent or ionic structures.

3) Properties of ceramics:

i. Very high melting and boiling points

- This is because most ceramics contain giant covalent or ionic structures. The covalent or ionic bonds holding them together is very strong, a lot of energy is required to overcome it.

ii. Does not conduct electricity or heat

- This is because there are no delocalized electrons or free moving ions present. Therefore most of them are electrical insulators.

iii. Chemically unreactive

- This is because all the electrons are held firmly in strong covalent bonds and not available for a reaction.

iv. Very hard

- This is because the ionic or covalent bonds holding them is very strong.

Uses of ceramics

1) Ceramics containing magnesium oxide are used:

- as electrical insulators in industrial electrical cables.
- as a refractory in furnace linings because it has a high melting point.
- in fire-resistant wall boards.

2) Ceramics containing aluminium oxide are used:

- as a refractory in furnace linings because it has a high melting point.
- as an abrasive for grinding hard materials because they do not conduct heat or melt when heat is given off during grinding.
- in transparent aluminium oxide-scandium windows.
- in high temperature and high voltage electrical insulators.
- in the replacement of artificial hip joints.

3) Ceramics containing silicon dioxide are used:

- as a refractory in furnace linings because it has a high melting point.
- as a abrasive, for example in sandpaper.
- in the manufacture of glass.