is used as a solvent and as a fuel, and is present in alcoholic drinks.

Ethanol can be produced in two ways.
1. By of sugars
The renewable raw materials (eg for wine or barley for beer) are mixed with water and yeast at just above room temperature in a batch . contains which are biological catalysts. The sugars react to form ethanol and dioxide. The carbon dioxide is allowed to escape and is prevented from entering the reaction vessel so that the ethanol is not oxidised. When the reaction is over ethanol can separated from the reaction mixture by [?] distillation.
2. By the addition of steam to
The reaction is carried out at a moderately high temperature and a high pressure in a continuous in the presence of a strong acid catalyst (phosphoric acid). Pure ethanol is produced but non-renewable fuels are used to maintain the reaction conditions and to provide from cracking crude .

Ethanol can be oxidised using oxygen to form acid. It is this oxidation of ethanol that results in alcoholic drinks turning sour. The steroid, cholesterol, contains the group -OH. Cholesterol is an essential chemical to humans but if too much is produced it can cause disease. Alcohols react reversibly with acids to form and water. is formed by the reaction of ethanoic acid with ethanol. Alcohols react with to form hydrogen.

acids form an homologous series where members contain the -COOH group. Vinegar contains acid. Ethanoic acid is used in the manufacture of the polymer fibre, acetate rayon. Oranges, lemons and many soft drinks contain a carboxylic , citric acid. Aspirin is a carboxylic acid. Aspirin is a drug used for pain relief and is taken regularly by those at risk from attacks. acid (vitamin C) is another carboxylic acid and is present in fresh fruit and vegetables. Carboxylic acids are [?] acids. They are neutralised by and they react with carbonates and hydrogencarbonates to produce a salt, carbon dioxide and water. Carboxylic acids react with in the presence of sulphuric to form esters. Concentrated sulphuric acid acts as a in this reaction. Esters are widely used as fragrances and food flavourings.

Most polymers (plastics) are made from compounds containing the -C=C- bond by polymerisation. Poly(chloroethene) is made from , CH₂=CHCl but the polymer is generally called poly(vinylchloride), PVC. Plastcs consist of a tangled mass of very long molecules in which the atoms are joined by strong bonds to form long chains. In a plastic the forces between the chains are weak so the plastic softens when heated and hardens again when ; this process may be repeated. Poly(ethene), poly(propene) and PVC are examples of thermosoftening polymers. When a thermosetting plastic is first heated covalent bonds are formed between adjacent chains. These strong cross-linkages prevent plastics from being softened and therefore from being re-moulded. Melamine (used in furniture) and many glues are examples of thermosetting polymers. Plastics (and other organic compounds) which contain and nitrogen produce poisonous fumes when burnt (hydrogen chloride and hydrogen cyanide respectively) especially where there is a limited supply of air; the combustion products of carbon and hydrogen are also formed.

Thermosoftening



Thermosetting



Living cells use chemical reactions to produce new materials. Yeast cells convert sugar into carbon dioxide and ethanol. This process is called and is used:
        to produce the alcohol, ethanol, in beer and wine;
        to produce the bubbles of carbon dioxide which make bread dough rise.
are used to produce yoghurt from milk. The convert the sugar in milk (lactose) to lactic acid. The chemical reactions brought about by living cells are quite fast in conditions that are warm rather than hot. This is because the cells use catalysts called . are protein molecules which are usually damaged by temperatures above about 45 °C. Different enzymes work best at different pH values.
Enzymes are involved in the following processes in the home:
biological detergents may contain protein-digesting and fat-digesting enzymes (proteases and lipases);
Enzymes are involved in the following processes in industry:
        are used to ‘pre-digest’ the protein in some baby foods;
        carbohydrases are used to convert starch syrup into sugar syrup;
        isomerase is used to convert glucose syrup into fructose syrup which is much sweeter than glucose and therefore can be used in smaller quantities in slimming foods.
In industry, enzymes are used to bring about reactions at normal temperatures and pressures that would otherwise require expensive, energy demanding equipment.
Successful industrial processes depending on enzymes usually:
        stabilise the organism to keep it functioning for a long period;
        immobilise the enzyme by trapping it in an inert solid support such as alginate beads;
        allow a process rather than a batch process.