Polymers. Grade 10. Polymers. Polymers are large molecules made when many smaller molecules join together. These small molecules are called monomers. Different polymers have different properties, so they have different uses. Ethene.
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Polymers Grade 10
Polymers • Polymers are large molecules made when many smaller molecules join together. • These small molecules are called monomers. • Different polymers have different properties, so they have different uses
Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Monomers and Polymers Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add the molecules together:
Polyethene • Ethene put under pressure and heated with a catalyst will polymerise to form poly(ethene). • Note that there are no double bonds in the polymer. • Poly(ethene) is an alkane. It is a saturated hydrocarbon. • A polymer which is formed from monomers added together where no other substance is produced is called an addition polymer.
H H H H C C C C H H H H Ethene Ethene Poly(e)thene H H H H C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Another way of drawing it… Instead of circles, let’s use letters… General formula for addition polymerisation:
Cl Cl H H C C C C H H H H Chloroethene Polychloroethene H Cl H Cl C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Another way of drawing it… Instead of circles, let’s use letters… Chloroethene General formula for addition polymerisation: Polypropene Propene
Problems with polymers • It can be difficult to dispose of polymers. • Most polymers, including polyethene and polypropene are not biodegradable. This means that micro-organisms cannot break them down, so they may last for very many years in rubbish dumps. • Polymers can be incinerated or burnt, but this can produce harmful waste gases. • Many polymers can be recycled, but it can be difficult and expensive to separate the different polymers from each other.