Monday, August 27, 2012

CBSE Class 8 - Science - Coal and Petroleum

Coal and Petroleum
Oil Drilling
(NCERT Chapter Answers and Q & A)


Q1:What are the advantages of using CNG and LPG as fuels?
Answer: The advantages of using CNG and LPG as fuels are:
  1. They are used as non-polluting fuels to transport vehicles.
  2. CNG is used for power generation and is a cleaner fuel.
  3. LPG can be used directly for burning in homes and factories.
  4. LPG and CNG has virtually no ash particles left after burning.

Q2:Name the petroleum product used for surfacing of roads.
Answer: Bitumen is the petroleum product used for surfacing of roads.



Q3: Describe how coal is formed from dead vegetation. What is this process called?
Answer: About 300 years ago, the earth consisted of dense forests in low lying wet lands. Due to natural processes, like flooding, these forests got buried under the soil. The temperature rose as they sank deeper and deeper and under high pressure these dead plants got slowly converted into coal.

The process of conversion of dead vegetation into coal is called carbonization as it contains mainly carbon. It is also known as fossil fuel since it is formed from the remains of vegetation.

Q4: Fill in the blanks:
Answer:
(a) Fossil fuels are coal, petroleum and natural gas.
(b) Process of separation of different constituents from petroleum is called refining.
(c) Least polluting fuel for vehicle is CNG.


Q5: Indicate whether the following statements are True (T) or False (F):
Answer
(a) Fossil fuels can be made in the laboratory. ✗ False
(b) CNG is more polluting fuel than petrol. ✗ False
(c) Coke is almost pure form of carbon. ✓ True
(d) Coal tar is a mixture of various substances. ✓ True
(e) Kerosene is not a fossil fuel. ✗ False


Q6. Explain why fossil fuels are exhaustible natural resources.
Answer: Fossil fuels are formed over a period of millions of years, by the action of heat and pressure on the remains of dead plants and animals. These fossil fuels are exhaustible natural resources because they can be exhausted by human activities. These fuels cannot be recreated in a short period of time.

Q7. Describe characteristics and uses of coke.
Answer: Coke is a tough porous and black substance. It is produced by destructive distillation of coal.
  1. It is an almost pure form of carbon.
  2. It is used as domestic as well as an industrial fuel in stoves and furnaces.
  3. It is used in the manufacture of steel.
  4. It gives little or no smoke.
  5. It is used for extraction of metals.
  6. It can be used to make fuel gases

Q8. Explain the process of formation of petroleum.

Answer: Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled down at the bottom of the sea and got covered with sand and clay. The absence of air, high pressure and high temperature for over million of years transformed the dead organisms into petroleum and natural gas. The petroleum deposits are usually found mixed with salt water. The petroleum is lighter than salt water, and hence, floats over it.

Q9.The following Table shows the total power shortage in India from 1991– 1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.

Sno.         Year           Shortage(%)
1 1991               7.9
2 1992 7.8
3 1993 8.3
4 1994 7.4
5 1995 7.1
6 1996 9.2
7 1997 11.5


Answer:

Q10: What are Inexhaustible Natural Resources? Give examples.

Answer: These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities. Examples are: sunlight, air.

Q11: Give examples of natural resources.

Answer: air, water, soil and minerals

Q12: What are Exhaustible Natural Resources? Give examples.

Answer: The amount of these resources in nature is limited. They can be exhausted by human activities. Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.

Q13: What is the composition of coal?

Answer: Coal is primarily made up of carbon, also hydrogen, oxygen, nitrogen and some traces of sulphur.

Coal Miner
Q14: How coal is obtained?

Answer: Coal is obtained through a process called mining. It is of two types.
  1. Surface mining: It is used when coal is found close to the surface or hillsides.
  2. Underground mining: This method is used to extract coal that is deep beneath the surface of the earth.
 Coal is processed in the industry to get useful products coke, coal tar and coal gas.

Q15: Where coke is used?

Answer: Coke is used in the manufacture of steel and in the extraction of many metals.

Q16: Where was the world's first oil well drilled?

Answer: Pennsylvania, USA, in 1859

Q17: What are the disadvantages of Petroleum?

Answer: Disadvantages are:
  1. Burning of petrol releases carbon dioxide into the air, which not only pollutes air but also contributes to global warming.
  2. Oil spills at sea have devastating impact on marine life and its surroundings.

Q18: Where is petroleum found in India?

Answer: In India, petroleum is found in Assam, Gujarat, Bombay high and in river basins of Godavari and Krishna.

Q19: What are the uses of  kerosene?

Answer: It is used as fuel stoves, lamps and for jet aircrafts.



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