QUIZ 14a. More on hydrocarbon molecules

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   addition      alkanes      alkenes      bromine      colourless      double      ethene      hydrocarbon      monomers      no      plastics      poly(ethene)      polymerisation      polymers      propene      reaction      saturated      single      small      substance      unsaturated      water   
(a) Image204.gif Carbon atoms form the spine of molecules. In the 1st molecule diagram on the left, all the carbon atoms are joined by covalent carbon carbon bonds and because of this bonding feature they are described as hydrocarbons and collectively known as the series.

(b) Image919.gif Other hydrocarbons have carbon carbon covalent bonds and because of this feature they are described as , and are known as the series of hydrocarbons illustrated by the 2nd example on the left.

(c) A simple laboratory test for an unsaturated hydrocarbon is to use . The yellow-brown colour of the testin reagent becomes as the bromine reacts with the unsaturated alkenes. There is with the alkanes.

(d) These unsaturated hydrocarbons from cracking are reactive and so are useful for making many other substances including . These consist of large molecules, and are formed when many molecules, of substances called , join together.

(e) This process is called . When unsaturated monomers join together to form a polymer with no other being produced in the reaction, the process is called polymerisation.

(f) Polymers are often commonly called and are made by polymerisation. For example, , often called polythene is made by polymerising the simplest alkene, . Another plastic called poly(propene) is made from .