Metals

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Metal Ages

Metals have played such an important role in the history of humankind, that entire ages have been named after them.

Around 6000 years ago, people discovered how to extract copper from copper carbonate (a copper compound). Before this discovery, the only metals in use had been gold, naturally occurring copper, and iron from meteorites. This extracted copperwas mixed with small amounts of ti (obtained from tin oxide), and made into bronze. The Bronze Age had begun. Broze had the advvantage of being very hard, non-corroding, and easy to re-melt and re-cast into new shapes.

Around 450 BC, bronze was replaced by iron, and so began the Iron Age. Iron was tougher than bronze (especially when combined with a small percentage of carbon to make steel), but it rusted easily. Therefore relatively few ancient steel tools and weapons remain.

This bronze Corinthian helmet was hammered out in Italy about 510 BC.

Properties of Metals

We are surrounded by things made of metal. What is it about metals that makes them so useful? All metals share certain properties. They are shiny (lustrous), dense, can be beaten into shapes without breaking (malleable), and are good conductors of heat and electricity. But they are not all equally good at these things.

Glossary

Key terms and definitions.

Aluminium is very easily rolled into extremely thin, flexible sheets for use as foil.

Tungsten's melting point is double that of iron, so it is used in light bulbs.

Lead is easily shaped and joined, so in the past it was used to make water pipes. (The Latin for lead is plumbum, which is where the word 'plumber' comes from.) Dissolved lead is quite poisonous, therefore copper, and more recently palstic, are now used for water pipes.

Gold is very dense and yellow, making it suitable for jewellery. Gold is also used as foil.

Copper is easily drawn into wires, and is an excellent electrical conductor.

Chromium is a very shiny and hard metal used for decoration (check out this car that is/was owned by Justin Bieber!)

Some metals are much more reactive than others, and are therefore unsuitable for manufacturing goods. What would happen if you made a cooking pan out of calcium, or a sink out of lithium?

Metals that have really big atoms have another very different property. The atoms of some of these metals break up, or are radioactive. As they break up, high-energy radiation is released. Radioactive metals are used in medicine, and in nucleear reactors, where the energy they release is used to heat water and run turbines to produce electricity.

Uranium-235 decay begins when a neutron strikes its unstable nucleus, causing the nucleus to split and produce smaller, more stable atoms. This releases a huge amount of heat energy, and ejects several neutrons. These newly freed neutrons can then collide with other U-235 nuclei, triggering more splitting events known as a chain reaction.

Alloys

Alloys are metals that have been mixed with other elements. Many metals are more useful as alloys than when used by themselves, as the combined properties of the elements give the alloy advantages that none of the elements have individually.

Copper can be combined to make more than 30 alloys, e.g. with tin (to make bronze), zinc, aluminium, phosphorus, nickel, silver and tungsten. All these alloys have different properties and uses.

The table shows some common alloys, their properties and uses.

The video below tells the story of the discovery of the alloy, duralumin.

Metals

Metal Ages

Properties of Metals

More on Metals

Glossary

Alloys