Metal
From Simple English Wikipedia, the free encyclopedia
Most of the world is made of nonmetals. Metals are a group of materials that are like one another in many ways. Some metals are aluminium, copper, iron, steel, tin, gold, lead, silver, titanium, uranium, and zinc.
The study of metals is very important and is called metallurgy.
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[edit] The ways that metals are alike (properties of metals)
Most metals are hard, shiny, they feel heavy (dense) and melt only when they are very hot. Lumps of metal will make a bell-like sound when they are hit with something heavy (they are sonorous). Heat and electricity can easily pass through a metal (it is conductive). A lump of metal can be beaten into thin sheet (it is malleable) or can be pulled into thin wires (it is ductile).
[edit] Use of metals
Metals are very useful to people. They are used to make tools because they can be strong and easy to shape. Iron and steel have been used to make bridges, buildings, or ships.
Some metals are used to make items like coins because they are hard and will not wear away quickly. For example copper (which is shiny and red in colour), aluminium (which is shiny and white), gold (which is yellow) , and silver and nickel (also white).
Some metals, like steel, can be made sharp so they can be used to make knives, axes or razors.
Metals with high value, like gold, silver and platinum are often used to make jewellery. Metals are also used to make fasteners and screws. Pots used for cooking can be made from copper, aluminium, steel or iron. Lead is very heavy and dense and can be used as ballast in boats to stop them from turning over.
[edit] Where metals come from
Metals are most often found in rocks on the Earth. Metals are sometimes found in sand because sand is rock that is worn away over a long time. Sometimes metals are found as large lumps inside rocks or sand, but most often metals are in the form of ore. Ores are a kind of rock with very small pieces of metal inside. To get the metal out, the ore is crushed and sometimes heated or chemicals are used.
The places where people get metals from the Earth are called mines. People sometimes dig mines making big holes in the ground, to get at the ore.
[edit] Alloys of metals
Many things that are made of metals may, in fact, be made of mixtures of at least one metal with either other metals, or with non-metals. These mixtures are called alloys. Some common alloys are:
- Steel (iron and carbon) (Carbon is a non-metal)
- Brass (copper and zinc)
- Bronze (copper and tin)
- Duralumin (aluminium and copper)
- Gunmetal (copper, tin, and zinc)
People first began making things from metal over 6000 years ago, when they discovered how to get copper from its ore. They then learned how to make a harder alloy, bronze, by adding tin to the copper. About 3000 years ago, they discovered iron. By adding small amounts of carbon to iron, they found that they could make a particularly useful alloy – steel.
[edit] Metals in chemistry
In chemistry, metal is a word for a group of chemical elements that have certain properties. It is easy for the atoms of a metal to lose an electron and become positive ions, or cations. In this way, metals are not like the other two kinds of elements - the nonmetals and the metalloids.
On the periodic table, we can draw a straight line from the element boron (symbol B) to the element polonium (symbol Po). The elements that this line passes through are the metalloids. The elements that are above and to the right of this line are the nonmetals. The rest of the elements are the metals.
Most of the properties of metals are because the atoms in the metal do not hold onto their electrons very tightly. Each atom is separated from the others by a thin layer of valence electrons. However, some metals are different. An example is the metal sodium. It is soft, melts at a low temperature, and is so light, it floats on water. People should not try this though, because another property of sodium is that it explodes when it touches water.
Most metals are chemically stable, and do not react easily. (Some of the metals do react. These are the alkali metals like sodium (symbol Na) and the alkaline earth metals like calcium (symbol Ca).) When metals do react, they often react with oxygen. The oxides of metals are basic. The oxides of nonmetals are acidic. However, most of the elements on the periodic table are metals.
Compounds, have metal atoms combined with other atoms to make molecules, are probably the most common things on the Earth. For example, common salt is a compound of sodium.
[edit] Metals in history
The use of metals is said to be the thing that makes people different from animals. Before they used metals, people made tools from stones, wood, and animal bones. This is now called the Stone Age.
No-one knows when the first metal was found and used. It was probably what is called native copper, which is sometimes found in large lumps on the ground. People learned to make this into copper tools and other things, although, for a metal, it is quite soft. When it was melted over fire, people learned how to make an alloy called bronze, which is much harder and stronger than copper. People made knives and weapons from bronze. This time in human history, after about 3300 BC is often called the Bronze Age, that is, the time of bronze tools and weapons.
Around the year 1200 BC some people learned to make iron tools and weapons. These were even harder and stronger than bronze and this was an advantage in war. The time of iron tools and weapons is now called the Iron Age . Metals have been very important in human history and civilization. Iron and steel were important in the making of machines. Gold and silver were used as money in order to allow people to trade, that is, exchange goods and services over long distances.
Many people thought that finding metals was a way to get rich. There have been many times when gold was found and people moved quickly in large numbers to those places for example, Central and South America after the year 1500, and many places after the year 1800 (the United States of America, Canada, Australia, New Zealand and South Africa). These are often called Gold Rushes.
[edit] Metals in astronomy
In astronomy, a metal is any element other than hydrogen or helium. This is because these two elements (and sometimes lithium) are the only ones that form outside stars. In the sky, a telescope can see the signs of metals and then the astronomer knows that there are stars.
