Most metals are solid at room temperature, but this does not have to be the case. Mercury is liquid. Alloys are mixtures, where at least one part of the mixture is a metal. Examples of metals are aluminium, copper, iron, tin, gold, lead, silver, titanium, uranium, and zinc. Well-known alloys include bronze and steel.
The ways that metals are alike (properties of metals)
Most metals are hard, shiny, they feel heavy and they melt only when they are heated at very high temperatures . 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 a thin sheet (it is malleable) or can be pulled into thin wires (it is ductile). Metal is hard to pull apart (it has a high tensile strength) or smash (it has a high compressive strength). If you push on a long, thin piece of metal, it will bend, not break (it is elastic). Except for cesium, copper, and gold, metals have a neutral, silvery color.
Not all metals have these properties. Mercury, for instance, is liquid at room temperature, Lead, is very soft, and heat and electricity do not pass through iron as well as they do through copper.
Use of metals
A bridge in Russia made of steel
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 color), aluminium (which is shiny and white), gold (which is yellow and shiny), and silver and nickel (also white and shiny).
Some metals, like steel, can be made sharp and stay sharp, so they can be used to make knives, axes or razors.
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:
People first began making things from metal over 9000 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.
On the periodic table, we can draw a zigzag line from the elementboron (symbol B) to the elementpolonium (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 due to the fact that 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 valenceelectrons.
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.
The use of metals is said to be one of the things that makes people different from animals. Before they used metals, people made tools from stones, wood, and animalbones. 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 coppertools and other things, although, for a metal, it is quite soft. They learned smelting to get copper from common ores. When copper 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 humanhistory, 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
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Metals have been very important in humanhistory 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, exchangegoods and services over long distances.
