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Across 1. Produced alongside carbon dioxide when fuel combusts. 8. Word describing two liquids that do not mix. 9. Advantage of biofuels versus fossil fuels. 14. Hydrocarbon with formula CnH2n 15. Poisonous gas produced when incomplete combustion occurs due to lack of oxygen. 17. Type of rock, that acts as a large carbon sink for the Earth. 18. Method for extracting plant oils. 19. In a symbol equation, (aq) indicates a substance is dissolved in water and stands for what? 20. Process for making ethanol from glucose

Down 2. Technique of mixing a metal with other elements in order to strengthen it. 3. Theory put forward by Alfred Wegener 4. Reaction of alkenes to make plastics 5. Process of adding hydrogen to oils to make margarine. 6. Salt of calcium formed when carbon dioxide is bubbled through limewater. 7. Subatomic particle with mass of one and charge of zero. 10. Series of metals that can be used to predict how they are extracted. 11. Method of separating aluminium from its ore 12. Simple test for unsaturation in organic molecules. 13. General type of reaction where oxygen is removed from a substance. 16. Supercontinent early in Earth's history