Across
- 2. product of petroleum
- 5. Fraction of petroleum
- 7. Main constitution of natural
- 9. purest form of carbon
- 11. absence of air
- 13. oil. Heaviest fraction of petroleum
- 14. natural gas obtained from methane
Down
- 1. Hard,black fossil fuel
- 3. process of separating petroleum
- 4. Fraction of petroleum
- 6. porous black substance
- 8. light fraction of petroleum
- 9. tar. Substance obtained from coal
- 10. coal used in road construction
- 12. gas. Fossil fuel cleaner than coal