The discovery of metals led to the progress of the civilization of man before that in the “Stone Age” man was using stone tools and weapons and later he switched over to metal tools and weapons.
He also studied the interaction of various metals and
nonmetals to prepare alloys and gradually improved the quality of life by
constructing buildings, using better fuels, taking care of health by inventing
better medicines and so on.
Today the prosperity of the country is measured by the production and
usage of quantities of metals and chemicals.
Properties of metals
All are solids at room temperature (mercury and gallium are
exceptions).
They are generally hard (sodium and potassium are soft and
can be cut with a knife).
They have high melting and boiling points.
Metals have high densities.
Metals are malleable. i.e., they can be beaten to form sheets.
They are ductile. The property of a substance that can be drawn
to rods and tubes is called ductility (zinc, arsenic and antimony are not ductile).
Metals have lustre (when they are cut, they have a brilliant
shine over the cut surface).
They are good conductors of heat and electricity.
They have high tensile strength (property of a substance that
can bear strain without breaking).
Metals are sonorous. (When struck with hard materials they
produce a ringing sound)
Uses of some common
metals
Metals like gold, silver, aluminium, mercury, copper and zinc
are some of the commonly used metals. Some of the uses of these metals are given
below
Gold
Gold is a bright yellow metal widely used by jewellers. It can
be drawn to thin wires and woven in sarees and other dress materials. It is
used in making coins of high value. It is used in filling cavities in teeth. In
the form of thin leaves or fine powder, it is used in some Ayurvedic medicines.
Silver
Silver is a bright white lustrous metal and is used in making
wires and ornaments. It is the best conductor of electricity and is used in
electric water purifiers and for making cutlery.
Its salts like silver bromide are used in making photographic
films, and silver iodide for seeding clouds for causing artificial rain. It is also
used in filling cavities of teeth and in ayurvedic medicine in the form of
powder or thin leaves. It is used in making high-quality mirrors.
Silver is a white lustrous metal but tarnishes because of
salt formation on exposure to air for a long time.
Copper
Copper is a reddish-brown metal. Its surface becomes dull
black or turns green due to the formation of compounds like oxide, and basic
carbonate etc., it is widely used as transmission wires, and cables because of its
superior conductive nature.
It is also used in
printed circuit boards in electronic devices like television, and transistors etc.,
It is used in making statues and coins. It is used in making alloys like brass
and bronze. It is used in making utensils.
Iron
Iron is a greyish-white metal in its pure state. It readily
gets rusted forming reddish brown ferric oxide in the hydrated form. Iron is
mostly converted to steel and widely used in construction materials, building
ships, automobiles, and railway bridges. It is also used in railway lines, many
kinds of machines, electrical transmission towers, TV towers, microwave towers
etc.,
Zinc
Zinc is a white metal with a bluish tinge. Though it is not
malleable and ductile it is widely used in galvanization. (Galvanization is the
process of coating hot steel products with molten zinc.
It is used to prevent the rusting of iron.) It is used as a negative
electrode in dry cells and making alloys such as brass and bronze.
Aluminium
Aluminium is a bright white metal and a good conductor of
electricity. It is highly malleable and ductile. It is used in making high-voltage transmission cables.
It is used for packing
medicines and food materials. Its alloys like duralumin and magnalium are very
light and strong. They are used in making aircraft frames, household fixtures,
components of automobiles, and utensils.
Aluminium paint prepared by mixing aluminium powder in
linseed oil is used for painting electric poles etc., to prevent rusting.
Mercury
Mercury is a silvery white metal and a good conductor of heat
and electricity. It is a liquid at room temperature having a boiling point of
357oC and a freezing point of -39oC.
It is used in thermometers in the laboratory as well as
clinical thermometers. Mixtures of mercury with metals like silver and gold are
called silver amalgam and gold amalgam respectively. Amalgams of metals like
silver and gold are used in dentistry for filling cavities.