Page 4 - Curriculum Visions Dynamic Book

(Below) Native gold.
1: Introduction
Metals are part of our everyday world, and we are familiar with, for instance, iron, silver, gold, copper, and aluminium in the things we use around us. But what do these, and all other metals, have in common, and what sets them apart from other materials?
Every metal is an element, that is, a substance that cannot be broken down into a simpler form. Most other materials, for example, ceramics and glass, are compounds of more than one element. Metals are inorganic materials, meaning they do not contain carbon. Examples of organic materials are plastics, wood, and oil.
Every metal can be bent, stretched, is shiny, and conducts electricity and heat well. That makes metals different from, for example, elements such as sulphur or phosphorus, which are very poor conductors of heat or electricity, and which are brittle.
How common are metals?
Metals are very common in the sense that they are a component of most substances. In fact, three-quarters of all of the chemical elements are metals. However, very few metals occur naturally as pure elements. Any that do – such as gold, silver, and copper – are called native metals.
Metals that appear in their native form do so because they do not easily combine with other substances. That is, they are chemically relatively unreactive. The fact that gold, for example, always occurs in its native form is what makes
it so instantly recognisable.
The majority of metals are, however, very reactive; as a result, they are not found in their native states. Iron and aluminium, for example, appear combined with other elements such as oxygen and sulphur. These compounds make up rocks that do not give any hint they contain metal.
See Vol. 1: Plastics, Vol. 3: Wood and paper, Vol. 4: Ceramics, and Vol. 5: Glass for more on these materials.
(Below) Native gold can be recovered from stream beds by panning. The gold is heavier than the other stones in the river and will stay behind on the pan when all of the sediment has been swirled away.
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