Sources of Energy

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Across
  1. 2. It is adark coloured, viscous and foul-smelling liquid.
  2. 7. fuels formed, from dead plants and animal matter burnied deep under the surface earth, over a period of millions of years.
  3. 11. it is a process of conversion of dead plant material into coal.
  4. 12. It is an inflammable gas.
Down
  1. 1. It has been used as a domestic fuel as well as in lanterns.
  2. 3. highly refined petrol is used as a fuel in aeroplanes.
  3. 4. oil It is viscous oil used for lubricating machines.
  4. 5. It is used as fuel in boilers
  5. 6. It is a black coloured viscous liquid.
  6. 8. the substance which produce heat on burning in air.
  7. 9. It has a carbon content of about 38 percent.
  8. 10. It is a hard and porous substance.