IB+Materials

  =**__Core. Topic 4. Materials. __**=

Although you have used a lot of different materials throughout your studies there are many other materials that you have not used but still **__MUST KNOW__** about. You must also know about the **physical** and **mechanical** properties of materials. Though designers, engineers and architects choose the materials they use for a variety of reasons, the principle reason for choosing a material remains the materials ability to do its job without failing. This ability to do a specified job is based on the properties of that material.

What do you need to know?
 * Properties of materials

The IB classify materials into these broad groups. Remember that no classification of materials is perfect.
 * Timber
 * Metals
 * Plastics
 * Ceramics
 * Composites

All materials are made up of atoms. Atoms join together to make [|molecules], they are held together with forces called bonds. These bonds can be Metallic bonds, Ionic bonds or Covalent bonds.


 * Ionic and covalent bonds. || Metallic bonds. ||
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Key terms that you must know.  compressive forces, shear, or bending, Deformation is often described as a strain. ||
 * Atom. || P - The smallest component of an element having the chemical properties of the element. ||
 * Molecule. || P - The simplest structural unit of an element or compound. ||
 * Alloy. || P - A mixture containing two or more metallic elements or metallic and nonmetallic elements. ||
 * Composite. || T - A composite is made up of different types of materials. The mix of materials will contribute their own ‘special’ properties. ||
 * Density. || T - This is a physical property. It means how much matter can 'fit' into its volume. ||
 * Electrical resistivity. || T - This is how strong a material can resist electrical current. It is measured in ohm meter (Ω m). ||
 * Thermal conductivity. || A - The ability of a material to transfer heat (flow). ||
 * Thermal expansion. || A - The ability of a material to resist sudden changes in temperature. ||
 * Hardness. || A - The resistance a material offers to penetration or scratching. ||
 * Tensile strength. || D - The ability of a material to withstand pulling forces. ||
 * Stiffness. || D - The resistance of an elastic body to deflection by an applied force. ||
 * Toughness. || D - The ability of a material to resist the propagation of cracks. ||
 * Ductility. || Ar - The ability of a material to be drawn or extruded into a wire or other extended form. ||
 * Plastic deformation. || Ar - A change in the shape or size of an object due to applied forces. This can be a result of tensile forces,
 * Fibre. || Ar - A single piece of a given material, elongated and roughly round in cross-section, often twisted with other fibres to form thread. ||