9701 · 20.1
Addition polymerisation flashcards
Revision flashcards for Cambridge 9701 Addition polymerisation (syllabus 20.1). Flip, recall, then mark a real past-paper question.
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What is a monomer?
A small molecule, such as an alkene, that can be joined together in large numbers to form a polymer.
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What is a polymer?
A long-chain macromolecule made up of many repeating monomer units.
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Define addition polymerisation.
A process in which many monomer molecules (containing a C=C double bond) join together to form a polymer, with no other product being formed.
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What is a repeat unit?
The specific arrangement of atoms in the polymer that is repeated along the chain. It is shown in square brackets with bonds extending outside.
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What essential structural feature must a monomer have for addition polymerisation?
A carbon-carbon double bond (C=C).
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What happens to the C=C double bond during addition polymerisation?
The weaker pi (π) bond breaks, and the electrons are used to form new single sigma (σ) bonds with adjacent monomer units.
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How do you name an addition polymer?
Put the name of the monomer in brackets and prefix it with 'poly'. For example, ethene polymerises to form poly(ethene).
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Why are addition polymers, like poly(ethene), generally unreactive?
Because their backbone consists of strong, non-polar C-C and C-H single bonds, which are not easily attacked by common reagents.
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What is a major environmental problem with addition polymers?
They are non-biodegradable, meaning they persist in the environment for hundreds of years, contributing to landfill and plastic pollution.
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COMMON TRAP: When drawing a repeat unit, what must you NOT include inside the brackets?
The C=C double bond. The double bond is broken to form the polymer chain, so the backbone of the repeat unit only contains C-C single bonds.
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How does addition polymerisation differ from condensation polymerisation?
In addition polymerisation, monomers add to each other with no loss of atoms. In condensation polymerisation, a small molecule, such as water, is eliminated for each bond formed between monomers.