SCIENCE STD.VII
Carbon and Its Allotropes
QI.
Answer the following questions:
Q1.Which element is found in diamond, coal and graphite?
Carbon.
Q2.Name the different forms in which carbon exist in nature.
. Carbon is found in the free state in the form of diamond, graphite and coal.
Q3.Define the term Allotropy. Give examples.
Allotropy is the existence of an element in different physical forms. All these physical forms
have same chemical properties.
The different physical forms of the element are known as allotropes and the phenomenon is
known as allotropy.
Q3. Give examples of the crystalline form of carbon and compare their structures.
i)
ii)
iii)
Diamond
Graphite and
Fullerene.
Diamond
Each Carbon atom is
linked with four other
carbon atoms in a
tetrahedral form.
This forms the
crystalline structure of
Diamond.
This basic unit repeats
itself and extends in all
Graphite
In Graphite each carbon
atom is linked with three
other Carbon atoms to form
a tri- gonal shape.
This is gives graphite a
sheet like structure.
This basic structure repeats
itself and arranges in a
hexagonal shape.
Fullerene
A molecule entirely
composed of carbon in
the form of a hollow, cage
like structure is called
Fullerene.
The number of carbon
atoms vary from 30 to
900.
directions to form an
Octahedral shape.
They are in two shape
Buckyballs and
Nanotubes.
Q4. Distinguish between crystalline and amorphous forms of carbon.
The difference between the Crystalline and Amorphous form of Carbon are
Crystalline Forms
They have regular shape and size.
They have definite geometrical forms,
sharp edges, and plane surfaces(these
forms are referred to as
Crystals.)
They have fixed melting and boiling
points.
Amorphous Forms
They do not have regular shape and size.
They do not have geometrical forms,
sharp edges and plane surfaces.
The melting and boiling temperatures
are high.
Diamond, graphite and fullerene and
crystalline forms of carbon.
The melting and boiling temperatures are
low.
Coal, charcoal and coke are amorphous
forms of carbon.
They do not have fixed melting and
boiling points.
Q7.Write down the Physical properties and uses of the following:}
i)
ii)
iii)
Diamond
Graphite and
Fullerene.
Physical Properties of Diamond:



Its the purest form of carbon.
Its colourless and lustrous crystalline solid.
Its the hardest substance known on the Earth.
Uses of Diamond:



Diamond is used as a precious gem in jewellery.
Its used in manufacturing of very thin wires such as tungsten.
It is used for cutting glass.
Physical Properties of Graphite:



Graphite is soft and flaky.
It is insoluble in any solvent.
It is a good conductor of heat and electricity.
Uses of Graphite:
 It is used a s an electrode.
 Used as a pencil lead
 It is used in nuclear reactor.

Physical Properties of Fullerene:



It is soluble in many solvents.
It is found in nature in small quantities
It is found in soot or interstellar dust.
Uses of Fullerene:
It is used as an insulator.
Its used as a catalyst.
It is used as a semi conductors in computers and flat screen tv.
Q8. What are the Amorphous form of Carbon.?
The amorphous forms of Carbon are charcoal, coal , lamp black ,gas carbon and coke.
Q9.What is Destructive Distillation ?
The process of heating organic substances strongly in the absence of air is known as destructive
distillation.
Q10.What is wood gas?
During Destructive distillation besides wood charcoal, bone charcoal or sugar charcoal a mixture
of gases is produced. These gases are carbon di oxide, carbon monoxide, methane and hydrogen
gas. The mixture of these gases is combustible and is called wood gas.
Q11. Which are the four varieties of Coal ? Which type of coal has the highest and which
has the lowest content of Carbon?
The four varieties of coal are Peat,Lignite ,Bituminous and Anthracite.
Peat has the highest content of carbon and Anthracite has the lowest carbon content .
QII.] Write True or False.
i)
ii)
iii)
iv)
Charcoal is black,soft and porous solid.
There are three varieties of coal.
Lamp Black is also called soot.
Coke produces smoke on burning.
QIII]. Choose the correct option to fill in the blank.
i)
ii)
iii)
iv)
v)
vi)
vii)
viii)
______________________(Allotropy/ Crystals) is the existence of a chemical
element in different physical forms.
__________________________(Crystalline/Amorphous) forms have regular shape
and size.
_________________________(Diamond/ Coal) is the crystalline form of carbon.
In diamond ,each carbon atom is linked with_______________________(four/six)
other carbon atoms.
In Graphite each Carbon atom is linked with ____________(three/six) other carbon
atoms.
______________________(Diamnod /Graphite) is a good conductor of heat and
electricity.
A molecule entirely composed of carbon in the form of a hollow cage like structure
is called _______________________(fullerene//semiconductors).
Fullerene is used as a ____________________(precious gem/ catalyst)
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