1. Materials 4.1.1
Define atom (160)
The smallest part of an element that can
exist chemically.
Define molecule (165)
Two or more atoms that are normally
bonded together covalently.
(outer electrons of some atoms come close
enough to over lap and are shared between
nuclei, thus forming a ‘covalent bond’). (see
4.5.1)

2. Materials 4.1.1
Define alloy (159)
A mixture that contains at least one
metal. This can be a mixture of metals or
a mixture of metals and non metals.
Define composite (160)
A mixture composed of two or more
substances (materials) with one
substance acting as the matrix (glue).

3. Materials 4.1.2
Describe a bond as a force of attraction
between atoms.

4. Materials 4.1.2
Three types of bonding.
1. Ionic (it is a bond formed by the
attraction between two oppositely
charged ions).
2. Covalent (4.5.1) page 61
3. Metallic. (4.4.1) page 60

5. Materials 4.1.3
Describe how materials are classified into
groups according to similarities in their
microstructures and properties.
Wood: Hardwood – Softwood –
Manufactured board.
Metal: Ferrous – Non ferrous – Alloys
Plastics: Thermoplastic – Thermoset –
Elastomer.

6. Materials 4.1.3
Ceramics: Glass – Clay
Composites: See later on.
We classify all these materials by what they
look like under the microscope.
They can also be listed according to their
properties. SEE LATER ON.

7. Materials 4.1.4
Explain that several classifications are
recognized but that no single classification
is perfect.
We recognise that materials have
similarities so we group them together.
But sometimes this ‘crude’ grouping of
materials from various groups is simply
only a convenient method.

8. Materials 4.1.5
Describe that, for this course materials are
classified into groups: timber, metals,
plastics, ceramics, food and composites:
and that some of these groups have
subdivisions.