alloys and polymers

What is an alloy?

A mixture of 2 or more elements, where at least one is a metal. Alloys are designed to have properties superior to those of their pure metal components.

Why are alloys typically harder than pure metals?

The atoms of the added element have a different size, which disrupts the regular lattice arrangement of the metal atoms. This makes it more difficult for the layers of atoms to slide over each other when a force is applied.

What is a polymer?

A large molecule (macromolecule) composed of many repeated subunits called monomers, which are joined together by covalent bonds.

Distinguish between addition and condensation polymerization.

1. Addition Polymerization: Monomers with double bonds (like alkenes) join together without the loss of any atoms.
2. Condensation Polymerization: Monomers join together with the loss of a small molecule, such as water (H_{2}O) or hydrogen chloride (HCl).

What are the characteristics of thermosoftening polymers?

These polymers consist of individual, tangled polymer chains with weak intermolecular forces between them. They melt when heated and can be reshaped multiple times.

What are the characteristics of thermosetting polymers?

These polymers have strong covalent cross-links between the polymer chains. They do not melt when heated and maintain their shape until they eventually char or decompose at very high temperatures.

Give examples of common alloys and their compositions.

• Steel: Iron (Fe) and Carbon (C).
• Brass: Copper (Cu) and Zinc (Zn).
• Bronze: Copper (Cu) and Tin (Sn).