Page 199 - ICSE Chemistry 8

Many proper es of diamond such as hardness, high density, high mel ng point (3500°C), high refrac ve
index and non-conduc ng nature are a ributed to its crystalline structure.
Value of Diamond

The value of a diamond depends upon its weight and the impuri es present in it. The weight of a diamond
is expressed in carats.
1 carat = 200 mg = 0.2 g Know Your Scientist
The famous Kohinoor diamond weighed Ferdinand Frederick Henri Moissan (1852–1907) was
186 carats. the fi rst person to prepare ar fi cial diamonds. In
The four C’s—carat, cut, colour and clarity 1892 he made his fi rst ar fi cial diamond for which
he prepared an electric-arc furnace. In that furnace,
best describe the quality of a diamond.
he heated a mixture of sugar charcoal and iron about
Colourless, transparent diamonds are the
4000°C. He proposed a theory that diamond could be
most expensive ones as they have negligible made through crystallisa on of carbon by placing it
impurity. under pressure using molten iron.

Properties of Diamond

• Pure diamond is a colourless, transparent substance with extraordinary brilliance. Raw diamonds
do not shine. They shine a er undergoing cu ng and
polishing procedures such that their angled-faces refl ect Thirst for Knowledge
light and break it into diff erent colours. It is the presence
• Black diamonds are the
of small traces of metallic oxides and salts that imparts
hardest of all.
dis nct colours to diamonds.
• Diamond is transparent to
• Diamond is the hardest natural substance known. visible light and X-rays. Using
-3
• Diamond has a high density of 3.5 g cm . X-rays, we can diff eren ate
• Diamond does not conduct electricity but it conducts between a fake diamond and
a real one.
heat extremely well.
• Diamond has high mel ng point of 3500°C. It sublimes when heated to this temperature.
• When diamond is heated to 800°C in the presence of oxygen, then only carbon dioxide gas is
formed. This shows that diamond is made up only of carbon.
• Diamond is insoluble in all solvents.
• Diamond does not react with any chemical.

Uses of Diamond
• Diamonds are used in instruments like glass cu ers and rock
drilling equipments.

• Diamonds are used for making jewellery because of their
extraordinary brilliance.
• Diamonds are used by eye surgeons as surgical tool to perform Fig. 9.3: Diamond jewellery
certain eye surgeries with great precision.
• Diamond dust is used for polishing other diamonds and valuable stones.

• Diamonds can withstand high radia on in space and are used for making protec ve windows for
spacecra s and satellites.

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