Page 52 - Science Class 08

EXTRACTION duc le, i.e., they can neither be beaten
Non-metals are also obtained from different into sheets nor drawn into wires.
sources as under: v Non-metals are bad conductors of heat and
v Nitrogen and oxygen are obtained from electricity in general–way, most of them
liquefied air by frac onal dis lla on. are insulators (non-conductors). But,

v Chlorine is extracted from crude, common graphite is a good conductor.
salt obtained from sea-water. v Non-metals are bri le (easily breakable).
v Sulphur is obtained either from sulphur So, if they are beaten, they crumble into
mines in free state or from sulphide ores powdery form.
where it is present in a combined form But, diamond is a non-metal that is the hardest
with various metals. substance known so far.
PHYSICAL PROPERTIES CHEMICAL PROPERTIES
v Non-metals may occur in any state— solid, Reac on with Oxygen
liquid or gaseous at normal temperature. Non-metals combine with oxygen to form acidic
For example, sulphur, carbon and iodine oxides.
are solids while bromine is a liquid. As for For example, sulphur forms sulphur dioxide on
oxygen, nitrogen and helium, they are combining with oxygen. It changes into
gaseous at normal temperature. sulphuric acid (H SO ) on reac ng with water
2 3
v Non-metals have low mel ng point and that changes blue litmus into red.
boiling point. Sulphur melts at 119°C while Reac on with Water
iodine at 113°C. Most non-metals are Non-metals do not react with water. Some of
gaseous at ordinary temperature. them are kept in water for their protec on
v Non-metals commonly appear dull to the against air. Phosphorus is a highly reac ve
eyes except iodine. element. If kept in the open air, it catches fire
v Non-metals occur in a variety of colours. and combines with oxygen of the air. So, it is
For example, sulphur is yellow, chlorine is stored in water.
pale green, phosphorus is either red or Reac on with Acids
white. Hydrogen, oxygen and nitrogen are Most of the non-metals do not react with acids.
colourless. But, sulphur reacts with hot strong nitric acid to
v Non-metals are neither malleable nor produce sulphur dioxide, nitrogen dioxide and
water.
S + 4HNO Õ SO + 4NO + 2H O
2
2
3
2
· Ancient people used small pieces of metal as they were. They valued them according to
their appearance or shine.
· About 3500 years ago, the Egyp ons started using pieces of metal as coins by indica ng
the value of each piece.
· In the earliest me, anyone could make coins, but soon the local governments took over
and official coins appeared around 3000 years ago in the Middle East.
· Metals are used for making coins even now. Copper, nickel, zinc, etc. are used in making
modern coins. That is why these are called coinage metals.

52 Science-8