Coal and petroleum

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Across
  1. 4. - The process of converting dead plants into a black substance used as a fuel (11 letters).
  2. 5. - The least polluting fuel for vehicles, known by its acronym (3 letters).
  3. 8. - Dark, rough, porous substance used in the production of steel (4 letters).
  4. 9. - abundant natural resources that are unlikely to be exhausted, such as sunlight and air (13 letters).
  5. 11. Compound of carbon and hydrogen
Down
  1. 1. - The process of separating different constituents from petroleum (8 letters).
  2. 2. - It is a non-renewable natural resource classified as a fossil fuel (4 letters).
  3. 3. - Thick, viscous liquid with an unpleasant odor, made up of various ingredients (9 letters).
  4. 6. - Dark, thick liquid made up of almost 200 different chemicals, used for various industrial purposes (8 letters).
  5. 7. - Petroleum product used for surfacing roads (7 letters).
  6. 10. Main gas released during the combustion of fossil fuels