Properties of Materials

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Metals:

Examples of metals include copper (Cu), zinc (Zn), gold (Au), silver (Ag), tin (Sn) and lead (Pb).

The following are some of the properties of metals:

• Thermal conductors:

Metals are good conductors of heat and are therefore used in cooking utensils such as pots and pans.

• Electrical conductors:

Metals are good conductors of electricity, and are therefore used in electrical conducting wires.

• Shiny metallic luster:

Metals have a characteristic shiny appearance and are often used to make jewellery.

• Malleable and ductile:

This means that they can be bent into shape without breaking (malleable) and can be stretched into thin wires (ductile) such as copper.

• Melting point:

Metals usually have a high melting point and can therefore be used to make cooking pots and other equipment that needs to become very hot, without being damaged.

• Density:

Metals have a high density.

• Magnetic properties:

Only three main metals (iron, cobalt and nickel) are magnetic, the others are nonmagnetic.

Non Metals:

In contrast to metals, non-metals are poor thermal conductors, good electrical insulators (meaning that they do not conduct electrical charge) and are neither malleable nor ductile. The non-metals include elements such as sulphur (S), phosphorus (P), nitrogen (N) and oxygen (O).

Metalloids:

Metalloids or semi-metals have mostly non-metallic properties. One of their distinguishing characteristics is that their conductivity increases as their temperature increases.

This is the opposite of what happens in metals. This property is known as semi conductance and the materials are called semi-conductors. Semi-conductors are important in digital electronics, such as computers. The metalloids include elements such as silicon (Si) and germanium (Ge).

Electrical conductors, semi-conductors and insulators:

An electrical conductor is a substance that allows an electrical current to pass through it. Electrical conductors are usually metals. Copper is one of the best electrical conductors, and this is why it is used to make conducting wire. In reality, silver actually has an even higher electrical conductivity than copper, but silver is too expensive to use.

An insulator is a non-conducting material that does not carry any charge. Examples of insulators are plastic and wood.

Semi-conductors behave like insulators when they are cold, and like conductors when they are hot. The elements silicon and germanium are examples of semi-conductors.

Thermal Conductors and Insulators:

A thermal conductor is a material that allows energy in the form of heat, to be transferred within the material, without any movement of the material itself.

An insulator is a material that does not allow a transfer of electricity or energy. Materials that are poor thermal conductors can also be described as being good thermal insulators.

Magnetic and Non-magnetic Materials:

Magnetism is a force that certain kinds of objects, which are called ‘magnetic’ objects, can exert on each other without physically touching. A magnetic object is surrounded by a magnetic ‘field’ that gets weaker as one moves further away from the object.

A metal is said to be ferromagnetic if it can be magnetized (i.e. made into a magnet).