METALS
Chemical elements can be divided into several groups. The largest group, forming about three-quarters of all elements, is the metals. Metals have several features that the other elements or non-metals lack. They carry heat and electricity very well compared to non-metals. They are solid at normal or room temperature. They are strong, hard and tough, and they can be polished to give a smooth, shiny surface. When they are squeezed under great pressure, they change shape or deform and become squashed, rather than splinter apart or shatter. These features are true of most metals, but not all. The metal sodium is very soft, while the metal mercury is a silvery liquid at normal temperature.
Metals are very important in the modern world. Because of their strength and hardness they are used to make all kinds of buildings, structures, machines and engines. The most widely-used metal in industry is iron – but not usually in its pure form. Iron is mixed with small amounts of other substances, especially carbon, to form steel. A metal mixed with other metals and substances like this is known as an alloy. There are hundreds of different kinds of alloy steels, each with slightly different amounts of carbon and other elements, and each designed to do a different task. Stainless steel is used for sinks and cutlery. Titanium and vanadium steels resist very high temperatures without melting.
A modern plane like the Boeing 747 Jumbo has more than four million parts, and many of these are made of metals. The main panels of the fuselage, wings and tail are aluminium. This metal is strong but very lightweight.
Not all metals stay hard and solid. Some can burn very brightly, especially in powdered form. Fireworks contain mixtures of powdered metals such as magnesium as well as other substances, to make them flare up with bright colours.
MAKING METALS
Very rarely a lump of pure metal is found lying on the ground, such as a gold nugget. But most metals occur inside rocks. Rock especially rich in a certain metal is called a metal ore. The metal is separated from its ore by various means. Iron is obtained from ores by heating them until they melt, a process called smelting.
Aluminium ore is known as bauxite. To separate the aluminium, it is treated with chemicals and electricity is passed through it, a process called electrolysis.
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