QUIZ 13a. Cracking, fuels and polymers

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   biodegradable      bottles      carbon      catalyst      cracked      crates      decomposition      dioxide      disposal      heating      hydrogen      methane      oxygen      petrol      poly(ethene)      poly(propene)      polymers      rain      ropes      smaller      sulphur      thermal      waste   
(a) Large hydrocarbon molecules can be broken down or to produce , more useful molecules. This process involves the hydrocarbons to vaporise them and passing the vapours over a hot . A reaction then occurs and some of the products of cracking are useful as fuels eg some more .

(b) Most fuels contain and/or hydrogen. The gases released into the atmosphere when a fuel burns are mainly carbon dioxide and water which is an oxide of . A typical word equation might be ...
(fuel) + (in air) ==> carbon dioxide + water

(c) Some fuels contain sulphur which burns to form . This is a lung irritant and the major cause of acid .

(d) Other products of cracking can be used to make plastics or . For example poly(ethene) and poly(propene). The plastic is used for making plastic bags and . The stronger plastic is used for making milk and . Most plastics, including poly(ethene) and poly(propene), are not broken down by microorganisms. Because they are not it causes problems with .