Selina Textbook Solutions: Carbon and Its Compounds | Chemistry Class 8 ICSE PDF Download

 Page 1


Carbon and Its Compounds 
Points to Remember: 
1. Carbon occurs in the earth’s crust in the free as well as in the combined state. 
2. In the free state, it occurs as coal, diamond and graphite. 
3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food 
nutrients and carbonates. 
4. Diamond is the hardest naturally occuring substance known. 
5. Fullerenes are discovered only recently. 
Exercise – I 
Question 1. 
Fill in the blanks. 
(a) Carbon is present in both living and non-living things. 
(b) The tendency of an element to exist in two or more forms but in the same physical 
state is calledAllotropy. 
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon. 
(d) Diamond is the hardest substance that occurs naturally. 
(e) The name ‘carbon’ is derived from the Latin word carbo. 
Question 2. 
Choose the correct alternative. 
(a) In combined state, carbon occurs as 
(i) coal 
(ii) diamond 
(iii) graphite 
(iv) petroleum 
(b) A crystalline form of carbon is 
(i) lampblack 
(ii) gas carbon 
(iii) sugar 
(iv) fullerene 
Question 4. 
Define the following terms: 
(a) Allotropy (b) Carat 
(c) Crystal (d) Catenation 
Answer: 
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists 
Page 2


Carbon and Its Compounds 
Points to Remember: 
1. Carbon occurs in the earth’s crust in the free as well as in the combined state. 
2. In the free state, it occurs as coal, diamond and graphite. 
3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food 
nutrients and carbonates. 
4. Diamond is the hardest naturally occuring substance known. 
5. Fullerenes are discovered only recently. 
Exercise – I 
Question 1. 
Fill in the blanks. 
(a) Carbon is present in both living and non-living things. 
(b) The tendency of an element to exist in two or more forms but in the same physical 
state is calledAllotropy. 
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon. 
(d) Diamond is the hardest substance that occurs naturally. 
(e) The name ‘carbon’ is derived from the Latin word carbo. 
Question 2. 
Choose the correct alternative. 
(a) In combined state, carbon occurs as 
(i) coal 
(ii) diamond 
(iii) graphite 
(iv) petroleum 
(b) A crystalline form of carbon is 
(i) lampblack 
(ii) gas carbon 
(iii) sugar 
(iv) fullerene 
Question 4. 
Define the following terms: 
(a) Allotropy (b) Carat 
(c) Crystal (d) Catenation 
Answer: 
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists 
in two or more forms in the same physical state with identical chemical properties but 
with different physical properties. 
(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g] 
(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or 
ions) are arranged in difinite pattern due to which they have definite geometrical shape 
with plane surfaces e.g. sugar and sodium chloride. 
(d) Catenation – The large number of organic compounds is due to the ability of carbon 
atom to form long chains with other carbon atoms through the sharing of electrons. This 
unique property of carbon is known as catenation. 
 
Question 5. 
State the terms: 
(a) Substances whose atoms or molecules are arranged in a definite pattern. 
– Crystals. 
(b) Different forms of an element found in the same physical state. – Allotropy. 
(c) The property by which atoms of an element link together to form long chain or ring 
compounds. – Catenation 
Question 6. 
Name the following: 
(a) The hardest naturally occurring substance. – Diamond. 
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite. 
(c) The third crystalline form of carbon. – Fullerenes. 
Question 7. 
Answer the following questions: 
(a) Why is graphite a good conductor of electricity but not diamond? 
(b) Why is diamond very hard? 
(c) What are fullerenes? Name the most common fullerenes. 
Page 3


Carbon and Its Compounds 
Points to Remember: 
1. Carbon occurs in the earth’s crust in the free as well as in the combined state. 
2. In the free state, it occurs as coal, diamond and graphite. 
3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food 
nutrients and carbonates. 
4. Diamond is the hardest naturally occuring substance known. 
5. Fullerenes are discovered only recently. 
Exercise – I 
Question 1. 
Fill in the blanks. 
(a) Carbon is present in both living and non-living things. 
(b) The tendency of an element to exist in two or more forms but in the same physical 
state is calledAllotropy. 
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon. 
(d) Diamond is the hardest substance that occurs naturally. 
(e) The name ‘carbon’ is derived from the Latin word carbo. 
Question 2. 
Choose the correct alternative. 
(a) In combined state, carbon occurs as 
(i) coal 
(ii) diamond 
(iii) graphite 
(iv) petroleum 
(b) A crystalline form of carbon is 
(i) lampblack 
(ii) gas carbon 
(iii) sugar 
(iv) fullerene 
Question 4. 
Define the following terms: 
(a) Allotropy (b) Carat 
(c) Crystal (d) Catenation 
Answer: 
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists 
in two or more forms in the same physical state with identical chemical properties but 
with different physical properties. 
(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g] 
(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or 
ions) are arranged in difinite pattern due to which they have definite geometrical shape 
with plane surfaces e.g. sugar and sodium chloride. 
(d) Catenation – The large number of organic compounds is due to the ability of carbon 
atom to form long chains with other carbon atoms through the sharing of electrons. This 
unique property of carbon is known as catenation. 
 
Question 5. 
State the terms: 
(a) Substances whose atoms or molecules are arranged in a definite pattern. 
– Crystals. 
(b) Different forms of an element found in the same physical state. – Allotropy. 
(c) The property by which atoms of an element link together to form long chain or ring 
compounds. – Catenation 
Question 6. 
Name the following: 
(a) The hardest naturally occurring substance. – Diamond. 
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite. 
(c) The third crystalline form of carbon. – Fullerenes. 
Question 7. 
Answer the following questions: 
(a) Why is graphite a good conductor of electricity but not diamond? 
(b) Why is diamond very hard? 
(c) What are fullerenes? Name the most common fullerenes. 
(d) What impurity is present in black diamond? 
(e) Explain the softness of graphite with reference to its structure. 
Answer: 
(a) In a graphite molecule, one valence electron of each carbon atom remains free, 
Thus making graphite a good conductor of electricity. Whereas in diamond, they have 
no free mobile electron. Thats why diamond are bad conductor electricity. 
(b) A diamond is a giant molecule. The number of valence electrons in carbon atom is 
four. As such each carbon atom is linked with four neighboring carbon atoms. Thus 
forming a rigid tetrahedral structure. It is the strong bonding’that makes diamond the 
hardest substance. 
(c) Fullerenes: Fullerenes are the third crystalline form of carbon. 
Though they were discovered only recently. They have.been found to exist in interstellar 
dust as well as in the geological formations of the earth. 
Common fullerenes are C – 32, C – 50, C – 70 and C – 76 
(d) Black diamonds have copper oxide present in them as impurity. 
(e) In a graphite molecule of each carbon atoms is linked with three neighboring carbon 
atoms. Thus forming a hexagonal arrangement of atoms. These hexagonal grouping of 
carbon atoms are arranged as layers or sheets piled one the top of other. The layers 
are held together by weak forces such that they can slide over one another. That is why 
graphite is soft. 
Question 8. 
Give two uses of (a) graphite (b) diamond. 
Answer: 
(a) Uses of graphite: 
1. For making the electrodes of electric furnaces. 
2. For making crucibles for melting metals due to its high melting points. 
(b) Uses of Diamond: 
1. Diamond is used in jewellery as a gem 
2. It is used for cutting and drilling rocks, glass, 
Question 9. 
Write three differences between graphite and diamond. 
Answer: 
Difference between diamond and graphite. 
Page 4


Carbon and Its Compounds 
Points to Remember: 
1. Carbon occurs in the earth’s crust in the free as well as in the combined state. 
2. In the free state, it occurs as coal, diamond and graphite. 
3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food 
nutrients and carbonates. 
4. Diamond is the hardest naturally occuring substance known. 
5. Fullerenes are discovered only recently. 
Exercise – I 
Question 1. 
Fill in the blanks. 
(a) Carbon is present in both living and non-living things. 
(b) The tendency of an element to exist in two or more forms but in the same physical 
state is calledAllotropy. 
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon. 
(d) Diamond is the hardest substance that occurs naturally. 
(e) The name ‘carbon’ is derived from the Latin word carbo. 
Question 2. 
Choose the correct alternative. 
(a) In combined state, carbon occurs as 
(i) coal 
(ii) diamond 
(iii) graphite 
(iv) petroleum 
(b) A crystalline form of carbon is 
(i) lampblack 
(ii) gas carbon 
(iii) sugar 
(iv) fullerene 
Question 4. 
Define the following terms: 
(a) Allotropy (b) Carat 
(c) Crystal (d) Catenation 
Answer: 
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists 
in two or more forms in the same physical state with identical chemical properties but 
with different physical properties. 
(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g] 
(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or 
ions) are arranged in difinite pattern due to which they have definite geometrical shape 
with plane surfaces e.g. sugar and sodium chloride. 
(d) Catenation – The large number of organic compounds is due to the ability of carbon 
atom to form long chains with other carbon atoms through the sharing of electrons. This 
unique property of carbon is known as catenation. 
 
Question 5. 
State the terms: 
(a) Substances whose atoms or molecules are arranged in a definite pattern. 
– Crystals. 
(b) Different forms of an element found in the same physical state. – Allotropy. 
(c) The property by which atoms of an element link together to form long chain or ring 
compounds. – Catenation 
Question 6. 
Name the following: 
(a) The hardest naturally occurring substance. – Diamond. 
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite. 
(c) The third crystalline form of carbon. – Fullerenes. 
Question 7. 
Answer the following questions: 
(a) Why is graphite a good conductor of electricity but not diamond? 
(b) Why is diamond very hard? 
(c) What are fullerenes? Name the most common fullerenes. 
(d) What impurity is present in black diamond? 
(e) Explain the softness of graphite with reference to its structure. 
Answer: 
(a) In a graphite molecule, one valence electron of each carbon atom remains free, 
Thus making graphite a good conductor of electricity. Whereas in diamond, they have 
no free mobile electron. Thats why diamond are bad conductor electricity. 
(b) A diamond is a giant molecule. The number of valence electrons in carbon atom is 
four. As such each carbon atom is linked with four neighboring carbon atoms. Thus 
forming a rigid tetrahedral structure. It is the strong bonding’that makes diamond the 
hardest substance. 
(c) Fullerenes: Fullerenes are the third crystalline form of carbon. 
Though they were discovered only recently. They have.been found to exist in interstellar 
dust as well as in the geological formations of the earth. 
Common fullerenes are C – 32, C – 50, C – 70 and C – 76 
(d) Black diamonds have copper oxide present in them as impurity. 
(e) In a graphite molecule of each carbon atoms is linked with three neighboring carbon 
atoms. Thus forming a hexagonal arrangement of atoms. These hexagonal grouping of 
carbon atoms are arranged as layers or sheets piled one the top of other. The layers 
are held together by weak forces such that they can slide over one another. That is why 
graphite is soft. 
Question 8. 
Give two uses of (a) graphite (b) diamond. 
Answer: 
(a) Uses of graphite: 
1. For making the electrodes of electric furnaces. 
2. For making crucibles for melting metals due to its high melting points. 
(b) Uses of Diamond: 
1. Diamond is used in jewellery as a gem 
2. It is used for cutting and drilling rocks, glass, 
Question 9. 
Write three differences between graphite and diamond. 
Answer: 
Difference between diamond and graphite. 
Diamond 
1. Pure diamond is colourless and transparent. 
2. It is the hardest naturally occurring substance. 
3. It has high density i.e. 3.5 g/cm
3
 
4. It is bad conduct of electricity. 
5. It bums in air at 900°C to form carbon dioxide. 
Graphite 
1. Graphite is greyish black opaque and shiny. 
2. It is soft and greasy to touch. 
3. It has low density i.e. 2.39 g / cm
3
 
4. It is good conductor of electricity. 
5. It bums in air at 700° C to form carbon dioxide. 
Exercise – II 
Question 1. 
Fill in the blanks: 
(a) Charcoal is formed when charcoal is burnt in a limited supply of air. 
(b) Coal is a amorphous form of carbon. 
(c) Peat is the most inferior form of coal. 
(d) Wood charcoal is a bad conductor of heat and electricity. 
(e) lampblack is used in making black shoe polish. 
Question 2. 
Choose the correct alternative 
(a) Anthracite is 
(i) an inferior type of coal 
(ii) a superior type of coal 
(iii) a cheapest form of coal 
(iv) none of above 
(b) Destructive distillation of coal yields 
(i) coal tar 
(ii) coal gas 
(iii) coke 
(iv) all of the above 
(c) Lamp black is 
(i) an amorphous form of carbon 
Page 5


Carbon and Its Compounds 
Points to Remember: 
1. Carbon occurs in the earth’s crust in the free as well as in the combined state. 
2. In the free state, it occurs as coal, diamond and graphite. 
3. In the combined state, carbon occurs in atmosphere (CO2) natural gas, food 
nutrients and carbonates. 
4. Diamond is the hardest naturally occuring substance known. 
5. Fullerenes are discovered only recently. 
Exercise – I 
Question 1. 
Fill in the blanks. 
(a) Carbon is present in both living and non-living things. 
(b) The tendency of an element to exist in two or more forms but in the same physical 
state is calledAllotropy. 
(c) Crystalline and non- crystalline are the two major crystalline allotropes of carbon. 
(d) Diamond is the hardest substance that occurs naturally. 
(e) The name ‘carbon’ is derived from the Latin word carbo. 
Question 2. 
Choose the correct alternative. 
(a) In combined state, carbon occurs as 
(i) coal 
(ii) diamond 
(iii) graphite 
(iv) petroleum 
(b) A crystalline form of carbon is 
(i) lampblack 
(ii) gas carbon 
(iii) sugar 
(iv) fullerene 
Question 4. 
Define the following terms: 
(a) Allotropy (b) Carat 
(c) Crystal (d) Catenation 
Answer: 
(a) Allotropy: Allotropy is defined as the phenomenon due to which an element exists 
in two or more forms in the same physical state with identical chemical properties but 
with different physical properties. 
(b) Carat – The weight of diamond is expressed in carats [ 1 carat = 0.2 g] 
(c) Crystal – A crystal is a homogeneous solid which particles (atoms, molecules or 
ions) are arranged in difinite pattern due to which they have definite geometrical shape 
with plane surfaces e.g. sugar and sodium chloride. 
(d) Catenation – The large number of organic compounds is due to the ability of carbon 
atom to form long chains with other carbon atoms through the sharing of electrons. This 
unique property of carbon is known as catenation. 
 
Question 5. 
State the terms: 
(a) Substances whose atoms or molecules are arranged in a definite pattern. 
– Crystals. 
(b) Different forms of an element found in the same physical state. – Allotropy. 
(c) The property by which atoms of an element link together to form long chain or ring 
compounds. – Catenation 
Question 6. 
Name the following: 
(a) The hardest naturally occurring substance. – Diamond. 
(b) A greyish black non- metal that is a good conductor of electricity. – Graphite. 
(c) The third crystalline form of carbon. – Fullerenes. 
Question 7. 
Answer the following questions: 
(a) Why is graphite a good conductor of electricity but not diamond? 
(b) Why is diamond very hard? 
(c) What are fullerenes? Name the most common fullerenes. 
(d) What impurity is present in black diamond? 
(e) Explain the softness of graphite with reference to its structure. 
Answer: 
(a) In a graphite molecule, one valence electron of each carbon atom remains free, 
Thus making graphite a good conductor of electricity. Whereas in diamond, they have 
no free mobile electron. Thats why diamond are bad conductor electricity. 
(b) A diamond is a giant molecule. The number of valence electrons in carbon atom is 
four. As such each carbon atom is linked with four neighboring carbon atoms. Thus 
forming a rigid tetrahedral structure. It is the strong bonding’that makes diamond the 
hardest substance. 
(c) Fullerenes: Fullerenes are the third crystalline form of carbon. 
Though they were discovered only recently. They have.been found to exist in interstellar 
dust as well as in the geological formations of the earth. 
Common fullerenes are C – 32, C – 50, C – 70 and C – 76 
(d) Black diamonds have copper oxide present in them as impurity. 
(e) In a graphite molecule of each carbon atoms is linked with three neighboring carbon 
atoms. Thus forming a hexagonal arrangement of atoms. These hexagonal grouping of 
carbon atoms are arranged as layers or sheets piled one the top of other. The layers 
are held together by weak forces such that they can slide over one another. That is why 
graphite is soft. 
Question 8. 
Give two uses of (a) graphite (b) diamond. 
Answer: 
(a) Uses of graphite: 
1. For making the electrodes of electric furnaces. 
2. For making crucibles for melting metals due to its high melting points. 
(b) Uses of Diamond: 
1. Diamond is used in jewellery as a gem 
2. It is used for cutting and drilling rocks, glass, 
Question 9. 
Write three differences between graphite and diamond. 
Answer: 
Difference between diamond and graphite. 
Diamond 
1. Pure diamond is colourless and transparent. 
2. It is the hardest naturally occurring substance. 
3. It has high density i.e. 3.5 g/cm
3
 
4. It is bad conduct of electricity. 
5. It bums in air at 900°C to form carbon dioxide. 
Graphite 
1. Graphite is greyish black opaque and shiny. 
2. It is soft and greasy to touch. 
3. It has low density i.e. 2.39 g / cm
3
 
4. It is good conductor of electricity. 
5. It bums in air at 700° C to form carbon dioxide. 
Exercise – II 
Question 1. 
Fill in the blanks: 
(a) Charcoal is formed when charcoal is burnt in a limited supply of air. 
(b) Coal is a amorphous form of carbon. 
(c) Peat is the most inferior form of coal. 
(d) Wood charcoal is a bad conductor of heat and electricity. 
(e) lampblack is used in making black shoe polish. 
Question 2. 
Choose the correct alternative 
(a) Anthracite is 
(i) an inferior type of coal 
(ii) a superior type of coal 
(iii) a cheapest form of coal 
(iv) none of above 
(b) Destructive distillation of coal yields 
(i) coal tar 
(ii) coal gas 
(iii) coke 
(iv) all of the above 
(c) Lamp black is 
(i) an amorphous form of carbon 
(ii) a crystalline form of carbon 
(iii) a pure form of carbon 
(iv) a cluster of carbon atoms 
(d) The process by which decayed plants slowly convert into coal is called. 
(i) petrification 
(ii) carbonisation 
(ii) carbonification 
(iv) fermentation 
(e) The purest form of the amorphous carbon is 
(i) wood charcoal 
(ii) sugar charcoal 
(iii) bone charcoal 
(iv) lampblack 
Question 3. 
Write ‘true’ or ‘false’ against the following statements: 
(a) Charcoal is a good adsorbent. True 
(b) Coke is obtained by destructive distillation of sugar. False 
(c) Activated charcoal is a good conductor of electricity. False 
(d) Wood charcoal is an important constituent of gun powder. True 
(e) Coal gas is used in the preparation of artificial ferilizers. False. 
Question 4. 
Define the following: 
(a) Carbonization 
(b) Adsorption 
(c) Bone black 
Answer:  
(a) Carbonization: The process of the slow conversion of vegetable matter into carbon-
rich substances is called carbonization. 
(b) Adsorption: Adsorption is the property due to which a substance absorbs gases, 
liquids and solids on its surface. 
(c) Bone black: The Carbon content of bone charcoal is separated by treating the latter 
with hydrchloride acid, which dissolves the calcium phosphate. Carbon is then filtered 
out of the solution and in this form it is called bone black.