Polymers, giant structures and alloys

The idea

Polymers are very long molecules with strong covalent bonds between the atoms in each molecule; the intermolecular forces between them are relatively strong, so they are solids at room temperature. Giant covalent structures, such as diamond, graphite and silicon dioxide, have very high melting points because many strong covalent bonds must be broken. Alloys are mixtures of metals with other elements; the different sized atoms distort the layers, so they cannot slide as easily, making alloys harder than pure metals.

1. Identify the structure type.
2. State what must be broken on melting.
3. For alloys, explain the distorted layers.

Watch out Pure iron is too soft for many uses; steels are alloys with carbon and other elements.