Metals make up about 3/4 of all elements and have several defining properties, including high melting points, conductivity of heat and electricity, strength and hardness. Metals are obtained from ores through extraction processes involving chemical reactions at high temperatures. Iron and steel rust when exposed to water and oxygen, but salt and acid rain can accelerate the process. Different metals like aluminum, copper, gold, and steel are used for various applications based on their properties and costs. Alloys are mixtures of metals that can enhance properties like hardness. Common alloys include brass and bronze. Most metals can be recycled to recover their materials.

1. Metals
What are metals?
About ¾ of all the elements that exist in nature are metals. They all have some special properties:
 state: metals have high melting and boiling points. At 20°C, except mercury, all metals are solid.
Mercury is the only liquid metal at room temperature.
 appearance:allmetals are shinywhen youfirst cut them or yourub them with sandpaper.
 sonority: when youhit a metal, it makes a ringing sound.Scientists say that metals are sonorous.
 conductionofheatand electricity: Metals are good conductors of heatand electricity:this means
that heat and electricity travel through metal easily.
 strenght and hardness: most metals are strong:big forcesare needed to break or squash them. Many
metals are also hard:it is not easy to scratchthem.
 density: most metals have a high density.Because of that, they feel heavy fortheir size.
 malleability and ductility: metals are malleable,whichmeans they can be hammered in shape
without cracking,and they are also ductile,whichmeans they can be pulled out to make wires.
Obtaining metals
Ores are naturally occurringrocks that contain pure metal, or metal compounds, in sufficient amounts to make
it worthwhileextracting them.
These rocksare broken in small pieces and then they undergo chemical reactions at high temperatures, to
obtain the pure metal.
Rusting
Iron and steel rust when they are exposed to water and oxygen: this is a form of corrosion,whichalters the
desired properties in metal.
Salt dissolved in water does not cause rusting, but it does speed it up, as does acid rain [acid rain: Rainthat
containsa highlevel of acids.It is believedto be causedbypollutionand, maybe,naturalactivity such asvolcanic
eruptions. ],which is due to pollution.
Uses of metals
We use different metals fordifferent jobs as they have different properties: it’s important to choose the right
metal foreach job. Here are some examples:
Metal Properties Uses
aluminium low density, does not corrode suitable for the bodies of planes and for foodcontainers
copper good conductorof electricity,
does not react with water
electrical wires, as it is a good conductor;
water pipes, due to its low reactivity
gold very good conductor of
electricity,unreactive
electrical connections on circuitboards, due to its
conductivity;
jewellery, due to its lackof reactivity
steel cheap and strong suitable for building material

2. Alloys
The properties of a metal can be changed by mixing other elements withit, such as carbon.
A mixture of twoor more elements, where at least one element is a metal, is called an alloy.
Alloys are harderthan the pure metal. Pure copper, gold and aluminium are too softfor many uses. So they are
mixed with other metals to make them harder for everyday use. For example:
 Brass,used in electrical fittings, is 70 % copper and 30 % zinc.
 Bronze,used in art, is made of copper and tin in variable percentage. Nowadaysit is mainly used for
statues, but it was used to make tools, weapons, armor, in ancient times, before iron use was developed.
 18 carat gold,used in jewellery,is 75 % gold and 25 % copper and other metals.
 Duralumin,used in aircraft manufacture, is 96 % aluminium and 4 % copper and other metals.
 Smart alloys (likenitinol,whichcontains titanium) can return to their original shape after being bent.
They are useful forspectacle frames, dental braces and surgical stents (thin tubes used to open up
damaged arteries).
Metal: alloys in euro coins
€1 and €2 are two-toned.
The yellow part is an alloy, 75% copper, 20% zinc and 5% nickel.
The gray part is made of an alloy called cupronickel,made of 75%
copper, 25% nickel.
The €0.10, €0.20 and €0.50 coins are a proprietary alloy knownas
"Nordic gold", consisting of 89% copper, 5% aluminium, 5% zinc
and 1% tin.
The €0.01, €0.02 and €0.05 coins are made of discs of steel, coated
with an alloy mostly made of copper (fourrées).The copper alloys
make the coinage antimicrobial.
Can metals be recycled?
Almost all metals can be recycled.
In the U.S., of the 132 million tonnes of metal needed every year, recycling contributes more than 50%.
In the UK, iron and steel make up the majority of the recycledmetal in use.
Recycledmetal is supplied mainly from industry, and increasingly frommunicipal and household waste.
Common examples of recyclingprocess involving metals include aluminium and tin/steel cans, and cars.