2. Ethanol can be produced industrially by the fermentation of sugar.

3. The sugar may come from sources such as molasses (a by-product of the sugar refining industry) or maize starch.

4. Fermentation needs yeast, single-celled fungi containing enzymes that catalyse the conversion of sugar to ethanol.

5. The mixture is maintained at around 40 °C.

6. Fermentation produces up to 15% ethanol by volume, which kills the yeast and stops the process.

7. Fermentation also produces carbon dioxide, which may be compressed and sold to fizzy drinks manufacturers.

8. Ethanol can be produced industrially by the hydration of ethene with steam.

9. A high temperature of about 300 °C is needed.

10. A high pressure of about 60 atmospheres, 6000 kPa, is also needed.

11. Concentrated phosphoric acid on a silica support is used as a catalyst.

12. The two main processes for the industrial production of ethanol, fermentation and hydration of ethene, have different characteristics.

13. They have different rates of reaction.

14. They produce different percentage yields of ethanol.

15. The purities of the initial products are different.

16. They have different energy needs and use different types of resources.

18. These are the advantages of producing ethanol by hydration of ethene.

19. These are the advantages of producing ethanol by fermentation.

20. Fermentation has economic and environmental advantages that mean it is often the process of choice, despite the advantages of the direct hydration of ethene.

21. Epoxyethane is a cyclic ether.

22. Epoxyethane has a three-membered ring structure.

25. The ring is strained, with smaller bond angles than usual for an ether. This makes epoxyethane highly reactive.

26. The carbon-oxygen bonds are easily broken and epoxyethane is readily hydrolysed by water.

27. The reaction produces an alcohol called ethane-1,2-diol (also known as ethylene glycol).

28. Ethane-1,2-diol is used as an antifreeze for car engines and in the manufacture of polyesters such as terylene.

29. Epoxyethane is manufactured by the reaction between ethene and oxygen.

30. A mixture of 5% to 20% ethene in air is heated to around 200 °C.

31. It is pressurised to around 20 atmospheres or 2000 kPa.

32. A finely divided silver catalyst is used to control the rate of reaction.

33. Epoxyethane is very hazardous and its manufacture must be controlled carefully to reduce the risk of explosion.

34. Epoxyethane is very hazardous and its manufacture must be controlled carefully to reduce the risk of explosion.