Using metals


The 19th century was the time when metals became cheap and widely used. The tin baths and other items in the picture above hint of this.
We still use an enormous variety of metals. Sometimes you can see the metal (as you saw in the picture of the aircraft on the previous screen), but most often we now cover up our metals with plastic or paint.
As you sit at your computer you can probably see a number of cables. Inside each one is a metal called copper. It has a light orangy, shiny surface. The copper has been made into a long wire. This is very flexible and allows the cable to be bent so you can arrange it tidily by your computer.
The copper is in the wire for one particular task - to carry electricity to all parts of your computer system. Copper, like all other metals, conducts electricity. It is covered in plastic because plastic is an insulator and so keeps other things around the cable (including you) protected from the electric current.


How can you tell a metal from other materials
A metal usually has a hard, smooth, shiny surface. If you touch it, it will feel cold. This is because it is a good conductor of heat and heat can therefore rapidly flow away from your skin. Metals are also good conductors of electricity. You may think an object is made of metal but cannot be sure because it is painted. If you are allowed to touch the object, do so. If it is metal it will feel cold.
What are the most widely used metals?
Steel is the most widely used metal. It is used for making things like cans, car bodies, girders, wire, cutlery, scissors, pins and paper clips. Iron is used for making car engines, manhole covers in the road, bolts, nails and chains. Aluminium is used for making things like the bodies of aeroplanes, buses, vans and caravans, overhead power cables, window frames, step ladders, pans and kitchen foil.

Copper is used for things like making electricity cables, pipes and radiators in central heating systems, and the bottom of some pans. Zinc is used for things like the casings of batteries and for coating steel to stop it from rusting. Lead is used for things like the inside of car batteries and to cover joints on some kinds of roofs such as church roofs. Gold is used for things like jewellery and for connecting wires to a microchip. It has also been used to make fillings in teeth. Silver is used for things like making jewellery, cutlery, trays, tea sets and ornaments.
What is the difference between iron and steel?
Iron is made by heating a rock called iron ore in a furnace. The ore is mixed with coke and limestone and then tipped into the top of the furnace. In the heat of the furnace, these materials change and molten iron is produced. The iron flows out of the bottom of furnace and is allowed to cool. In the iron is carbon from the coke. Steel is made by heating up the iron again and blowing oxygen through it. This takes out most of the carbon. Iron with only a little carbon in it is the metal we call steel. Steel has more useful properties than iron and so is used more widely.


Do metals have different properties?
Yes. That is why different metals have different uses. For example, we use copper for wires for carrying electricity instead of iron because copper is more flexible and does not rust. If iron were used in cables in the wall it might rust, break and stop electricity flowing. It is also not as good a conductor as copper.
Aluminium is used to make aeroplanes instead of steel because it is only a third as heavy. If aeroplanes were made of steel they would need much more powerful engines, much more fuel and longer runways to get them into the air.
Do all metals rust?
No. Although we use iron and steel very widely, and both these metals rust, most metals do not rust. Rusting happens when iron or steel is left in damp conditions for a long time.
However, many metals will tarnish, that is they will change colour or become duller. This happens because of the effect of the oxygen in the air. The surface of a metal which has been changed in this way can be cleaned. Rust, however, cannot be cleaned.
Can metals be mixed together?
Yes they can. To mix metals they have to be heated until they melt. A mixture of two or more metals can be made. A mixture of metals is called an alloy. The alloy has properties which are different from each of the metals in the mixture.
Many different alloys are made because they have useful properties. For example steel, nickel and chromium are mixed together to make stainless steel. This alloy does not rust and is used for making cutlery.
How are metals made into different shapes?
Three processes used to shape metals are casting, rolling and drawing. In casting, the metal is molten and poured into a mould. This way it is possible to make a complicated shape such as a car engine.
In rolling, a metal sheet is made by squashing a piece of metal between rollers.
In drawing, a metal wire is made by heating a piece of metal and pushing it through a piece of metal with a hole in it. The hot metal pushes its way through the hole and this is gripped a pulled hard. The rest of the hot metal is then drawn through the hole to make the wire.