NCERT Class VIII Science Solutions: Chapter 5-Coal and Petroleum Part 6

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Question 30:

While driving what are the tips we must follow to save petrol/ diesel/natural gas?

Answer:

  1. Ensure correct tyre pressure.

  2. Ensure regular maintenance of the vehicle.

  3. Drive at a constant and moderate speed.

  4. Switch off the engine at traffic lights or at a place where you have to wait.

Question 31:

Imagine that all the exhaustible natural resources are exhausted by human activities. Do you think survival of living beings would be possible? If yes, why? If not, why not?

Answer:

If all the exhaustible natural resources are exhausted by human activities, then the survival of living beings would not be possible. Actually, fossil fuels are the most important source of energy for us today.

They are concentrated source of energy and give off heat and light on burning. The heat can be used to cook food or to run engines such as automobile engines. It can be used to generate electricity as in powerhouse where the most common fuel used in coal.

Image of Exhaustible resources

Exhaustible Resources

Image of Exhaustible resources

Question 32:

Why petrol is exhaustible natural resource, whereas sunlight is not? Explain.

Answer:

The natural resources which are present in a limited quantity in nature and can be exhausted by human activities are called exhaustible natural resources e.g. coal, petroleum, natural gas, minerals, forest, wildlife etc.

It requires millions of years for the conversion of the dead organism into petroleum from which petrol is separated. So, once the present stock of it gets exhausted, no new supplies of it will be available to us in the near future, whereas sunlight is present in an unlimited quantity in nature, so it is an inexhaustible natural resource. It is not likely to be exhausted by human activities.

Question 33:

Write some important uses of the various constituents of petroleum.

Answer:

  • Petroleum gas in liquid form (LPG) — used as fuel for home and industry

  • Petrol — used as fuel for automobile and aviation

  • Kerosene — used as fuel for stoves, lamps and for jet aircrafts

  • Diesel — used as fuel for heavy motor vehicles, electric generators

  • Lubricating oil — used for lubrication

  • Paraffin wax — used in ointments, candles, Vaseline etc.

  • Bitumen — used in paints and road surfacing

Question 34:

Coal reserves are said to be enough to last for another hundred years. Do you think we need to worry in such case? Why or why not?

Answer:

Yes, the known resources of coal will last only for about 100 years. Once the present stock of coal present in the earth gets exhausted, no new supplies of these fossil fuels will be available to us in the near future because it take millions of years to convert the dead organisms into fossil fuels in nature.

So, coal should be used with care and caution and not wasted at all.

Question 35:

What steps would you suggest for the judicious use of fossil fuels?

Answer:

  1. We should use fossil fuels only when absolutely necessary.

  2. We can also use natural gas as a substitute. The reserves of natural gas discovered by us have gone up ten time within 20 years.

  3. Alternatives sources of energy such as solar, wind and should be used in place of fossil fuels.