5. Coal And Petroleum Science class 8 in English Medium ncert book solutions Chapter Review

Chapter Review:

• Petroleum 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.
• These resources are present in unlimited quantity in nature is called Inexhaustible. Examples are: sunlight, air.
• The amount of these resources in nature is limited are called exhaustible. Examples of these resources are forests, wildlife, minerals, coal, petroleum, natural gas etc.
• The dead remains of living organisms (fossils). So, these are all known as fossil fuels.
• As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation.
• Coke is a tough, porous and black substance. It is almost pure form of
  carbon.It is used in the manufacture of steel.
• Coal tar is a black, thick liquid  with unpleasant smell. It is a mixture of about 200 substances.
• Petrol and diesel are obtained from a natural resource called petroleum.
• The world’s first oil well was drilled in Pennsylvania, USA, in 1859.
• Great commercial importance, petroleum is also called ‘black gold’.
• The process of separating the various constituents fractions of petroleum is known as refining. It is carried out in a petroleum
  refinery.
• Natural gas is a very important fossil fuel because it is easy to transport through pipes.
• CNG is used as a fuel for transport vehicles because it is less polluting.