Chemistry Online for GCSE and O-Level

• Charges on the ions and electrons hold the structure together, but allow the ions to slide over each other. This is why metals can be bent and stretched i.e. they are malleable
• The free electrons allow the metal to conduct electricity and heat as they can move through out the metal structure.

Organic Compounds and Fuels

Petroleum, coal and natural gas are natural sources of fossil fuels.

Methane is the main constituent of natural gas.

Petroleum is a mixture of hydrocarbons. It can be separated into useful fractions by fractional distillation.

Commercial Uses of Esters (Esters are sweet smelling liquids)

(i) used as artificial flavour in sweets, cakes and fruit juices

(ii) used a solvent for nail varnish

Esterification – reaction of alcohol with carboxylic acids

(i) Ethanol + ethanoic acid à ethyl ethanoate + water

C₂H₅OH + CH₃COOH à CH₃COOC₂H₅ + H₂O

Conditions: heat with a little concentrated sulphuric acid

(ii) butanol + propanoic acid à butyl propanoate + water

C₄H₉OH + C₂H₅COOH à C₂H₅COOC₄H₉ + H₂O

(iii) propanol + butanoic acid à propyl butanoate + water

C₃H₇OH + C₃H₇COOH à C₃H₇COOC₃H₇ + H₂O

Proteins can be hydrolysed back into amino acids.

Proteins can be broken back into amino acids by refluxing the protein with dilute hydrochloric acid

Fats are ester molecules possessing the same linkages as Terylene but with different units.

Proteins possess the same amide linkages as NYLON but with different units.

Polyethene (polythene), polyester and margarine are man-made polymers.

However, carbohydrates, proteins and fats are macromolecules that occur naturally.

Synthetic fibres are said to be non-biodegrable i.e. they cannot be broken into simpler substances by bacteria.

Thus, it is not easy to dispose (get rid of) them.

One method is by burning them but here they produce harmful combustion products like CO, soot and HCl (PVC).

Uses of nylon

(a) To make hard-wearing fabrics

(b) To make strong ropes (Polyurethane)

Uses of terylene

(a) Used as substitutes for cotton (Dacron clothing) and wool in the textile industry

(b) Used as the bonding resin in glass fibre plastics

(c) Made as tape (Mylar) which is magnetically coated for use in tape recorders and videotape machines