Chemistry · Bonding, Structure and Properties of Matter
Polymers
Spec 5.2.2.5📙 Higher
Theory · read, then commit
Polymers are very large molecules made from many small repeating units called monomers, joined into long chains. The joining process is called polymerisation.
🔹Monomer
A small molecule that can join with others — e.g. ethene, CH₂=CH₂.
⛓️Polymer
The long chain formed from thousands of monomers — e.g. poly(ethene).
🔁Repeating unit
Written in brackets with n outside: [—CH₂—CH₂—]ₙ.
Checkpoint · quick check
State what is meant by a monomer.
1Addition polymerisation uses monomers that contain a C=C double bond.
2The double bond opens up — one bond breaks and frees a pair of electrons.
3Those electrons form a new bond to the next monomer.
4The monomers link into a long saturated chain (no double bonds left) — and no atoms are lost.
Checkpoint · quick check
Describe how a polymer forms from monomers.
🧊Solid at room temperature
Long chains and reasonable intermolecular forces keep polymers solid and flexible.
🚫Electrical insulators
No free electrons or ions, so they do not conduct electricity.
🔥Thermoplastic vs thermosetting
Thermoplastics soften when heated and reshape; thermosetting polymers form cross-links and stay hard.
Checkpoint · quick check
Explain why poly(ethene) is a solid at room temperature.
📐 Key Equations
n CH₂=CH₂ → [—CH₂—CH₂—]ₙ (poly(ethene))
Retrieval · Match the Polymer to its Monomer
Test yourself · 9 questions, exam order
⭐Examiner Tip
Don't call a polymer a giant covalent structure. It is a large molecule whose chains are held to each other by weak intermolecular forces — that is why it melts far below diamond, where strong covalent bonds run all the way through. That force difference is where the comparison marks are.
0 of 9 answered
Warm-up · 2 questions
Explain why polymers have much lower melting points than giant covalent structures such as diamond.
Ethene (CH₂=CH₂) can be used to make poly(ethene), but ethane (C₂H₆) cannot. Explain why.
Exam standard · 3 questions
Explain, in terms of the double bond, how addition polymerisation forms poly(ethene) from ethene.
Explain why a polymer with longer chains tends to have a higher melting point than one with shorter chains.
PVC is stiffer and higher-melting than poly(ethene). Suggest why, in terms of intermolecular forces.
Stretch · 4 questions
Explain why melting a polymer does not break the covalent bonds along its chains.
In addition polymerisation, explain why no small molecule is lost when the monomers join together.
Describe the repeating unit of poly(ethene) and explain how it relates to the ethene monomer.
Explain why polymers are described as having a simple molecular structure, even though the molecules are very large.
Key note · cover it, say it, check it
Revision card · 6 stepsPolymers
01Polymer: long chain of repeating monomer units.
02Addition polymerisation: monomers with C=C double bonds join together.
03Properties depend on chain length and intermolecular forces.
04Solid at room temperature, flexible, insulators.
05Thermoplastic: soften on heating.
06Thermosetting: permanently hard.
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