Page 201 - ICSE Chemistry 8

• Graphite burns in air at 700°C to form carbon dioxide.
• Graphite is insoluble in most solvents. It can be converted into diamond at a very high temperature
and pressure.

Activity 9.2

Aim: To show that graphite is a good conductor of electricity
Materials required: A graphite rod, a ba ery, a bulb, a switch, battery switch
/
connec ng wires
Procedure connecting wire

• Connect a graphite rod to a ba ery, bulb and a switch
with the help of connec ng wires as shown in the fi gure.
graphite rod
• Now close the circuit with the help of the switch.
Observa on: The bulb glows.

Conclusion: This shows that graphite conducts electricity.

Uses of Graphite

• Due to its so ness, powdered graphite is used as a lubricant for fast moving
parts of machinery.
• Graphite is a good conductor of electricity due to which it is used for making
carbon electrodes or graphite electrodes in dry cells and electric arcs.
• Graphite is used for making pencil lead.
• Graphite is used to make black paint and printer’s ink because it is black in
colour and insoluble in water. Fig. 9.5: Pencils
• Graphite is used as a moderator in nuclear reactors to slow down fast-moving par cles.
• Graphite is used in making crucibles for mel ng metals due to its high mel ng point.

The diff erences between diamond and graphite are shown in Table 9.2.

Table 9.2: Diff erences between Diamond and Graphite
Diamond Graphite

• Pure diamond is transparent and colourless. • Graphite is greyish-black, opaque solid with shiny texture.
• Diamond is the hardest known naturally • Graphite is soft and slippery (greasy) to touch.
occurring substance.
-3
-3
• The density of diamond is 3.5 g cm . • The density of graphite is between 1.9 to 2.3 g cm .
• Diamond is a bad conductor of electricity. • Graphite is a good conductor of electricity.
• Diamond burns at about 800°C. • Graphite burns at about 700°C.

Fullerenes (Buckminsterfullerene)

A spherical, crystalline allotropic form of carbon consis ng of 60 atoms was discovered in 1985 by three
scien sts—Harry Kroto, Robert Curl and Richard Smalley. This allotropic form is called fullerene.

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