Page 53 - Science Class 08

USES OF NON-METALS v Bronze, a combina on of copper (metal)
Non-metals are useful in various ways:
v Oxygen is essen al for life. It also helps
combus on in homes, industry and aircra .
v Nitrogen is not widely used in its natural
form. In compounded form, it provides the
plants with necessary nutrients.
v Chlorine can kill germs. So, it is used in
purifica on of water.
v Sulphur is used in making sulphuric acid
which is so useful in industry.
v Iodine is used to make ncture of iodine
that is applied on wounds as it is an sep c.
v Silver nitrates are used in photography.
v Sulphuric acid is used to make sulphates
while nitric acid to prepare nitrates.
v Feldspar is used to make porcelain and
china dishes.
v Gypsum is used to make cement.
v Mica is used as an electrical insulator in
irons and toasters.
v Monozite is used in make nuclear fuel.
v Quartz is used in electronic equipments –
watches, telephones, radios and also in the
manufacture of glass.
v Rock-salt is used as common salt in foods
and for food preserva on as well as in
chemical industry.
v Talc is used to make talcum powder.
ALLOYS
Alloys are metallic compounds composed of
one metal and one or more metal or non-metal
element.
Examples of common alloys are as follows:
v Steel, a combina on of iron (metal) and
carbon (non-metal).
Science-8
and n (metal).
v Brass, a mixture of copper (metal) and zinc
(metal).
Many alloys are made up of a metal used as the
base metal. It mixes with one or more other
metals or non-metals.
Why are Alloys Made?
Several metals in their pure form are too much
so or rust-prone. They may have some other
mechanical or chemical limita ons. But, when
mixed with other metals or non-metals, they
become strong, an -rust and also can overcome
its mechanical and chemical limita ons.
Just like innumerable shades of colours, the
number of possible alloys is countless. Most
alloys are made by mel ng two or more metals
together and then alloying them to cool down
and harden.
For example, bronze is an alloy made by mixing
copper with n in the ra o 7:1.
The commonest alloys are those of iron; as:
v Iron + a li le carbon makes steel that is
used to make rail-tracks, bridges and also
many machines.
v Iron (80.6%) + chromium (18%) + nickel
(1%) + carbon (0.4%) are used to make
stainless steel.
v Iron (87%) + manganese (13%) gives an
extremely strong and tough steel. It is
prepared by hea ng it at 1000°C and then
cooling it down in water quickly.
v Magnets are made from an alloy called
alnico. It is made by mixing aluminium,
nickel, cobalt and steel.
v German silver is an alloy made by mixing
copper (60%), zinc (25%) and nickel (15%).
53