Addition Polymerisation (Cambridge (CIE) A Level Chemistry): Flashcards
Exam code: 9701
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Define addition polymerisation.
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Define addition polymerisation.
An addition polymerisation is a reaction in which many monomers containing at least one C=C double bond join together to form long polymer chains as the only product.
What bond change occurs in the monomer during addition polymerisation?
The π-bond in the C=C double bond breaks. The monomers then link together to form new C-C single bonds, producing the polymer chain.
True or False?
Addition polymerisation produces two products: the polymer and a small molecule such as water.
False.
Addition polymerisation produces only one product — the polymer. No small molecules are released, which distinguishes it from condensation polymerisation.
In addition polymerisation, the small reactive molecules that join together are called ........... The long-chain molecule they form is called a ............
In addition polymerisation, the small reactive molecules that join together are called monomers. The long-chain molecule they form is called a polymer.
Define repeat unit.
A repeat unit is the smallest group of atoms that, when connected one after another, makes up the polymer chain. It is shown in square brackets in structural and displayed formulae.
How does the repeat unit of a poly(alkene) differ from its monomer?
The repeat unit is identical to the monomer except that the C=C double bond is replaced by a C-C single bond. The repeat unit shown in brackets in a displayed formula is not the monomer itself.
True or False?
Poly(chloroethene), also known as PVC, is made by the addition polymerisation of chloroethene monomers.
True.
Chloroethene (CH2=CHCl) undergoes addition polymerisation. The C=C bond opens and the monomers link to form poly(chloroethene), commonly called PVC.
Poly(ethene) is formed by the addition polymerisation of ........... The repeat unit has a ....... bond between the two carbon atoms instead of a double bond.
Poly(ethene) is formed by the addition polymerisation of ethene. The repeat unit has a single bond between the two carbon atoms instead of a double bond.
How can you identify the monomer from a displayed formula of an addition polymer?
Locate the repeat unit shown inside square brackets. The monomer is the same as the repeat unit, but with the C-C single bond replaced by a C=C double bond.
Define non-biodegradable.
A non-biodegradable material is one that cannot be broken down by microorganisms. Poly(alkenes) are non-biodegradable and can take hundreds of years to decompose in landfill.
Why are poly(alkenes) described as resistant to chemical attack?
Poly(alkenes) are very large alkane-like molecules. They are unreactive and do not undergo chemical reactions, making them resistant to chemical attack by most reagents.
True or False?
Burning poly(alkenes) is an environmentally safe method of disposal because they combust completely to give only carbon dioxide and water.
False.
Burning poly(alkenes) produces harmful combustion products that pollute the environment. Complete combustion to CO2 and H2O is not always achieved, and toxic gases can be released.
Poly(alkenes) are ..........-biodegradable and can take up to ....... of years to decompose when disposed of in .......... sites.
Poly(alkenes) are non-biodegradable and can take up to hundreds of years to decompose when disposed of in landfill sites.
Give three reasons why the disposal of poly(alkenes) is a major environmental challenge.
They are unreactive and resistant to chemical attack.
They are non-biodegradable, persisting in landfill for hundreds of years.
Burning them produces harmful combustion products that pollute the environment.
True or False?
Poly(alkenes) are non-biodegradable because they are unreactive large alkane-like molecules.
True.
The unreactivity of poly(alkenes) means microorganisms cannot break them down. This is the root cause of their non-biodegradability and long persistence in landfill.
Define landfill.
Landfill is a method of waste disposal in which materials are buried underground. Non-biodegradable poly(alkenes) persist for hundreds of years in landfill, causing long-term environmental pollution.
Dumping poly(alkenes) in landfill causes long-term ........... Burning them releases ....... combustion products into the atmosphere.
Dumping poly(alkenes) in landfill causes long-term pollution. Burning them releases harmful combustion products into the atmosphere.
What chemical property of poly(alkenes) makes them useful as plastics but also problematic for disposal?
Their unreactivity (resistance to chemical attack) makes them durable and useful as plastics. However, the same property means they are non-biodegradable and persist in the environment for very long periods.
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