Q39. State some characteristics of petroleum.
Ans. Characteristics of petroleum
It is a dark oily liquid.
It has an unpleasant odour.
It is a mixture of various constituents
such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
Q40. Explain the process of formation of petroleum.
How is natural gas formed?
Ans. Petroleum was formed from organisms living in the
sea. As these organisms died, their bodies settled at the bottom of the sea and
got covered with layers of sand and clay. Over millions of years, absence of
air, high temperature and high pressure transformed the dead organisms into
petroleum and natural gas.
Q41. Write uses of coal tar.
Ans. Products obtained from coal tar are used as starting
materials for manufacturing various substances used in everyday life and in
industry, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic
materials, roofing materials, etc. Interestingly, naphthalene balls used to
repel moths and other insects are also obtained from coal tar.
Q42. What are the uses of coal?
State some uses of coal.
Ans. Uses of coal
Coal is one of the fuels used to cook food.
Earlier, it was used in railway engines to
produce steam to run the engine.
It is also used in thermal power plants to
Coal is also used as a fuel in various
Q43. What are the advantages of using CNG and LPG as fuels?
advantages of using CNG and LPG as fuels are:
They can be transported easily through
They can be used directly for burning in
homes and factories where it can be supplied through pipes.
They are clean fuels and do not give smoke
They are less polluting.
Q44. State some of the tips of PCRA to conserve petrol and
Give the tips advised by PCRA to save petrol/diesel while
Drive at a constant and moderate speed as
far as possible,
Switch off the engine at traffic lights or
at a place where you have to wait,
Ensure correct tyre pressure, and
Ensure regular maintenance of the vehicle.
Q45. Describe how coal is formed from dead vegetation. What is
this process called?
Where do we get coal from and how is it formed?
Ans. About 300 million years ago the earth had dense forests
in low lying wetland areas. Due to natural processes, like flooding, these
forests got buried under the soil. As more soil deposited over them, they were
compressed. The temperature also rose as they sank deeper and deeper. Under
high pressure and high temperature, dead plants got slowly converted to coal.
As coal contains mainly carbon, the slow process of conversion of dead
vegetation into coal is called carbonisation.
Q46. Distinguish between inexhaustible and exhaustible natural
These resources are present in unlimited quantity in nature and are not
likely to be exhausted by human activities.
The amount of these resources in nature is limited. They can be exhausted by
Examples of these resources are sunlight and air.
Examples of these resources are forests, wildlife, minerals, coal, petroleum,
natural gas etc.