From Wikipedia, the free encyclopedia

Metals are amongst our most valuable resources. Thousands of years ago, people used metals such as copper and iron to make weapons and everyday objects. These metals are still in use today.

The five most used metals in order of use are: iron, aluminum, copper, zinc, and manganese.

The general physical properties of metals are:

• are hard and strong.
• solids (Only mercury is liquid at room temperature).
• shiny (when polished).
• good conductors of heat.
• good conductors of electricity.
• dense
• malleable and ductile.
• sonorus

The properties of metals make them suitable for different uses in daily life.

• copper, gold and silver are good conductors of electricity and are ductile. Therefore copper is used for electrical cables and gold and silver are used for electrical connections.

• Iron and steel are both hard and strong. Therefore they are used to construct bridges, buildings and motor cars. The disadvantage of using iron is that is tends to rust.

• Aluminium is a good conductor of heat and is malleable. It is used to make saucepans and thin foil.

It is also used to make aeroplane bodies as it is a low density metal.

• Gold and silver are very malleable ductile and very unreactive. They are used to make intricate jewellery which does not tarnish.

a coil of solder

An alloy is a metal mixed with other elements. The properties of an alloy is different from pure metals. Some alloys are listed below.

• steel:contains iron and carbon plus other metals. It is stronger than pure iron. It is used as girders for buildings and car bodies.

• solder:it is a mixture of tin and lead. It has a lower melting point than pure metals. It is used for connecting electrical circuits.

• duralumin:contains aluminium and copper. It is lighter than copper and stronger than aluminium. It is used in aeroplanes and alloy wheels.

The black surface is lead oxide. The white surface is the lead viewd when the lead oxide is scratched.

Many substances on the Earth's surface will at sometime come in contact with air, water or acids. The shiny surface of most metals becomes dull in time. This is due to a slow chemical reaction between the surface of the metal and oxygen in the air. The reaction forms only one product; a surface coating of the metal oxide. The general word equation is: metal+oxygen → metal oxide

For example: The dull appearance of the metal lead is due to a coating of lead oxide. lead+oxygen → lead oxide

If the surface is scratched then the shiny lead metal can be seen underneath.

Heating can speed up the reaction with oxygen. If a piece of copper is heated it quickly becomes coated in black copper oxide. The word equation is:

copper + oxygen → copper oxide