Detailed explanations in West Bengal Board Class 8 Science Book Solutions Chapter 4 Occurrence of Carbon and its Compounds in Nature offer valuable context and analysis.
WBBSE Class 8 Science Chapter 4 Question Answer – Occurrence of Carbon and its Compounds in Nature
Multiple Choice Questions & Answers : (1 mark for each question)
CNG is used as –
i) cooking gas
ii) fuel of vehicles
iii) generation of electricity
iv) preparation of bricks
ii) fuel of vehicles
Domestic, industrial and agricultural wastes are used to produce-
ii) bio fuel
iii) bio gas
iii) bio gas
Combustion of fossil fuel may cause-
i) global warming
ii) acid rain
iii) respiratory diseases
iv) ail of the above
iv) all of the above
At normal temperature and 60 atmospheric pressure Carbon dioxide is converted to –
iv) none of the above
Carbon dioxide is –
i) lighter than air
ii) blue in colour
iii) completely soluble in water
Polythene is used in making –
i) carry bags
iii) cup plate
i) carry bags
Teflon is –
iii) poor conductor of slectricity
iii) poor conductor of slectricity
PVC is used to prepare –
i) nonstick utensils
iv) cup plate
Of total mass of human body carbon is-
i) 5 0 %
ii) 30 %
iii) 10 %
iv) 80 %
i) 50 %
State whether True or False : (1 mark for each question)
1. Diamond is harder and denser than graphite.
2. 60 % of carbon dioxide generated through human activitiesis absorbed by the oceans.
3. Graphite is not a conductor of electricity.
4. Fullerenes are not macromolecules.
5. Coal is used as a fuel of vehicles.
6. Snails and corals absorb carbon dioxide dissolved in water and form their shells.
7. Some anaerobic bacteria can convert carbon monoxide to organic compounds.
8. CNG is used for cooking.
9. Taptapani hot spring is situated in Odissa.
10. Bio-diesel is prepared from vegetable oils or animal fat.
11. Polythene is not insulator of slectricity.
12. Methanogenic bactria in wetlandsproduce methane.
Fill in the blanks : (1 mark for each question)
1. Of the entire mass of human body, carbon comprises ______ of the total mass.
2. In the shell of snail or other marine animals there is ______.
3.Synthesis of diverse organic molecules by living organisms is known as ______.
4. Methane is one of the ______ gas.
5. In room temperature heat conductivity of diamond is greater than any other ______.
6. Graphite is ______ of electricity.
7. The symbol of fullerene molecule is ______.
8. Temperature of the centre of earth is ______.
9. The ______ oil can be used directly in diesel generators or engines without purification.
10. Neutrons and protons are bound in a nucleus by an energy called ______.
11. A target is set to generate ______ megawatt of electricity by 2032.
12. ______ is a pungent-smelling corrosive gas.
13. Urea is used as the major ______ fertiliser.
14. Temperature of solid carbon dioxide is ______.
15. The increase of temperature of the atmosphere due to green house effect is called ______.
16. ______ is produced through the digertion of organic waste in absence of air.
2. Calcium Carbonate
8. 6000° C
10. Nuclear energy
12. Sulphur dioxide
14. 78° C
15. global warming
Match the following : (1 mark for each question)
a) Match the column A with column B.
|Column A||Column B|
|a) Teflon is used||i) water-resistant fibre.|
|b) Polythene is used to||ii) finished fuel.|
|c) Nylon is a||iii) energy.|
|d) Carbon dioxide is||iv) make carry bags.|
|e) Carbon dioxide is used||v) is still hot.|
|f) Bio gas is useci as a||vi) less amount of heat.|
|g) The core of the earh||vii) a colourless gas.|
|h) The refining of coal||viii) to prepare non-stick utensils.|
|i) Low-grade coal produces||ix) to produce urea.|
|j) Fuels are the sources of||x) is called coal washing.|
a) Teflon is used to prepare non-stick utensils.
b) Polythene is used to make carry bags.
c) Nylon is a water-resistant fibre.
d) Carbon dioxide is a colourless gas.
e) Carbon dioxide is used to produce urea.
f) Bio gas is used as a finished fuel.
g) The core of the earh is still hot.
h) The refining of coal is called coal washing.
i) Low-grade coal produces less amount of heat.
j) Fuels are the sources of energy.
Very Short Questions & Answers : (1 mark for each question)
Name two elements which have allotropy forms.
Carbon, Sulphur can have more than one allotrope.
How many carbon atoms exist in fullarene?
60 or 70 carbon atoms exist in fullerene.
In which industry fullerene is used?
In electronics and medicine industry fullerene is used..
In which form carbon can make mark on a paper?
Graphite can make mark on a paper.
In which form carbon is a good conductor of heat and electricity?
Gas Carbon is a good conductor of heat and electricity.
Which form of carbon looks like a football?
Write name of two green house gases.
CO2 and methane are two green house gases.
What compound CO gas makes with Hacmoglobin?
Which form of carbon dissolves in organic solvent?
Fullerene dissolves in organic solvent.
What is water gas?
The mixture of CO and H2 is called water gas.
Which form of carbon can cut glass?
Diamond can cut glass.
Which form of carbon is called ‘a bucky ball’?
If diamond is strongly heated in presence of air what is produced?
Carbon dioxide gas is produced.
Which oxide of carbon is poisonous?
Carbon monoxide (CO).
What is bourt?
Black coloured not transparent diamond is called bourt.
What is producer gas?
The mixture of carbon monoxide and nitorgen (CO + N2).
What is ‘non-biodegradable’polymers?
The artificial polymers made by man are called ‘non-biodegradable’ polymers.
What is Dry Ice?
Solid carbon dioxide is called Dry lce..
What is bio fuel?
Bio fuel means the fuel produced from assimilated food in plants and microbes.
What is coal washing?
The refining of coal is called coal washing.
Short Questions & Answers : (2 marks for each question)
What is allotropes?
When an element can be found in more than one physical form, then the different physical form in which the element sxists are called its allotrope.
What are the allotropes of carbon?
The allotropes of carbon are commonly divided into two categories-1. crystalline and 2. amorphous.
Crystalline “rms of carhon are-i) diamond, ii) graphite iii) fullerene. A morphou forms of carbon are- i) charcoal, ii) lamp black, ifi) coke. (v) gas carbon.
What is Coal Washing?
Lifting Coal from coal mines and purifying it by different methods is called coal Washing. As a result a low-smoke and lowash coal can be produced separating various impurities present in coal.
What is Water gas and Producer gas?
Mixture of Carbon monoxide and Hydrogen gas is called water gas C ± H2 O → Mixture of Carbon monoxide and Nitrogen gas is called producer gas. When limited air is passed over extremely heated coke then we get C ± N2 O →
Name some alternative sourses of energy apart from traditional fuels.
Some alternative sources of energy apart from traditional fuels are-i) Solar energy, ii) Wind energy, iii) Geo-thermal energy, iv) Bio-fuels, v) Atomic energy.
Long Questions & Answers : ( 3 marks for each question)
Write the physical properties of diamond.
i) Diamond is a transparent, colourless solid. Most naturally– occuring diamonds contain small amount of impurities. ‘vhich impart colour to them.
ii) Diamond bends the light rays passing through it as it has a high refractive index of 2.47 . It is because of this property that properly cut and polished diamond sparkles brightly.
iii) It has a high density of 3.5 g / cm3.
iv) It has a high melting point of about 3500° C.
v) It is the hardest natural substance. Oniy a diamond can cut another diamond.
vi) It is a poor conductor of heat and electricity.
Write uses of diamond.
a) As properly cut and polished diamond sprerkles brightly, it is used in jevellery:
b) Diamond absorbs harmiful radiation. Hence, it is used in space satellites to make radiationproof windows.
c) Because of its hardness, diamond tipped tools are used for cutting and drilling of rocks.
d) Diamond is used to cut glass. :
Write physical properties of graphite.
- Graphite is an opaque solid, grey-black in colour.
- It is a soft and slippery material.
- Its density is 2.2 g / cm3.
- It remains stable at high temperatures and possesses a high melting point of 3700° C.
- It is a good conductor of heat and electricity.
How is Biogas and Bio-fuel produced?
Biugas is produced through the digestion of crganic waste in absence of air. It can be used as a finished fuel. In this anaerobic digestion, mainly methane is produced. so this is called biological methane production or bio-methanetion. Domestic, industrial and agricuitural wastes are ured in this process.
Biofuel means the fuel produced from assimiiated food in plarts and miciobes. In sur country production of biofuel means the cultivation of Jatropha plants and processing of oil from its seeds to prepare bio-diesel. The Jatropha oil can be used directly in diesel generators or engines without purification.
Write the physieal properties of Carbon dioxide.
- Carbon dioxide is heavier than air. It can be poured from one jar to another like a liquid.
- It is colourless, has a faint smell and an acidic taste.
- It turns moist blue litmus into red. Hence, it is acidic in nature.
- It is fairly soluble in water. Its solubility increases with pressure forms carbonic acid in water.
- It does not support combustion and is not a combustible gas.
- It can be solidified at -80° C. Solid carbondioxide is called dry ice.
Write some uses of Carbon dioxide.
a) Preparation of urea : Nitrogenous fertilisers are needed for good crop. Urea is used as the nitrogenous fertiliser. Urea is produced by reacting Carbon dioxide with ammonia.
b) Production glass: Modern civilization is unbelievable without glass. Soda(Na2 CO3) is required for preparation of glass. Vast amount of carbondioxide is required to manufacture glass.
c) For making fire-extin guishter and to prepare solid carbon dioxide.
To prepare different soft-drinks and to extinguish fire, carbon dioxide is needed though it can not be used for fire caused by oil or metal. If carbon dioxide is cooled to -80° C, it becomes a solid. Solid carbon dioxide is called dry-ice. It is a useful refrigerating solid as it does not wet. It is used for food presevation.
How can we maintain the balance of CO2 and O2 in atmosphere?
i) We have to preseve our forests and plant trees in cities and towns so that plant absorbs CO2 from atomsphere will be converted in O2 and the balance would be maintained.
ii) Everyday we burn fossil fuels and generate millions of tonnes of CO2 that reaches atmosphere. We have to reduce the use of fossil fuel and increase the use of natural gas, hydrogen etc in vehicles. This will prevent the increase in CO2 level in the atmosphere.
iii) To produce electricity we should have to decrease the use of coal and increase the use of solar energy, geo-therma! energy, nuclear energy and tidal energy to produce electricity, to stop the increase of CO2 level in atmosphere.
What is green house effect?
Gas molecules in the atomsphere can not absorb the solar infrared, so it heats up the earth. Some of the absorbed energy gets dissipated through materials in the surroundings. The rest of the energy is re-emitted by the earth. Molecules of some gases in the atomsphere carbon dioxide (CO2), water vapour (H2O), nitrous oxide (N2O), methane (CH4), ozone (O3) and the chlorofluorocarbons-absorb this low-energy infrared radiation emitted by the earth. As a result some heat cannot reach the outer space and gets trapped in the atmosphere. This phenomenon is known greenhouse effect.
What is global warming?
With the increased industrialisation, burning of fuels in homes and rising population more CO2 is released. On the other hand, the decreasing vegetation and deforestation is leading to less CO2 utilisation in photosynthesis. The level of CO2 in the atmosphere is increasing steadily for the past three hundred years. Scientists are worried that someday in near future the green-house effect due to CO2 will be so large that it will increase the temperature of the atmosphere. Such a possible warming effect is called global warming that may even melt the polar ice caps.
Write the Hazardous effects on environment due to combustion of fossil fuels.
1. From the combustion of fuels like wood, coal, petroleum etc. the unburnt carbon particles are spread in the environment. These cause respiratory disese like Asthma.
2. The incomplete burning of such fuels produces carbon monoxide which is a poisonous gas. So burnig of cola or other carbonaceous fuel in a closed room is very harmful and can even cause death.
3. CO2 mixes with air on burning most of the fuels. It is increase in CO2 in the atomosphere that is held responsible for global warming.
What are polymers define. Write two main reasons for the use of different polymers.
Polymers are compounds make from smaller units. Many molecules, similar or different, combine chemically to form such chain-like long molecules. The long chain molecule formed by the joining of a large number of monomers is called polymer. Cotton, silk, wool and jute are naturallyoccuring polymers. Polyethylene, polystyrene, poly vinyl chloride (PVC) and bakelite are synthetic polymers. These are called plastics.
Two main reasons for the use of different polymers in place of the previously used substances are-(i) The life of artificial polymers is longer (ii) during preparation of different objects they can be moulded as necessary.
From text book (page-149-150)
Fill in the blanks given below:
(a) FbCO3 + 2 HNO3 = ________ + CO2 + H2 O
(b) CaCO3 + 2 HCl = ________ + CO2 + H2 O
(c) Na2 CO3 + H2 SO4 = _____ + CO2 + H2 O
(d) MgCO3 + + = MgCl2 + CO2 +
(e) NaHCO3 + HCl = Nacl + ________ + H2 O
(a) PbCO3 + 2 HNO3 = Pb(NO2)2 + CO2 + H2 O
(b) CaCO3 + 2 HCl = CaCl2 + CO2 + H2 O
(c) Na2 CO3 + H2 SO4 = Na2 SO4 + CO2 + H2 O
(d) MgCO3 + 2 HCl = MgCl2 + CO2 + H2 O
(e) NaHCO3 + HCl = NaCl + CO2 + H2 O