Polymers
Practise Polymers for GCSE Chemistry with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Polymers are very large molecules with strong covalent bonds and fairly strong intermolecular forces, so they are solid at room temperature.
Free downloads
These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Polymers are very large molecules made when many small molecules, called monomers, join together in a repeating chain.
The atoms in a polymer molecule are linked by strong covalent bonds. Because the molecules are so large, the intermolecular forces between polymer chains are relatively strong — much stronger than between small molecules.
That is why polymers are solid at room temperature, unlike many simple molecular substances which are gases or liquids. But the intermolecular forces are still weaker than ionic or covalent bonds, so polymers melt at lower temperatures than giant covalent structures.
Revision notes
Structure
A polymer is a very large molecule formed when many monomers join together.
The atoms within the polymer molecule are linked by strong covalent bonds. Polymers are represented by a repeating unit shown in brackets with the letter n.
Why polymers are solids
Because polymer molecules are very large, the intermolecular forces between the chains are relatively strong.
More energy is needed to overcome them than for small molecules, so polymers are solid at room temperature rather than gases or liquids.
Comparison with other structures
Polymers have stronger intermolecular forces than simple molecular substances, so higher melting points.
But those forces are still weaker than the bonds in giant covalent or ionic structures, so polymers melt at much lower temperatures than diamond or sodium chloride.
Key points
- A polymer is a very large molecule made from monomers.
- Monomers join in a repeating chain.
- Atoms in a polymer are linked by covalent bonds.
- Intermolecular forces between chains are relatively strong.
- Polymers are solid at room temperature.
- Polymers melt below giant covalent structures.
Worked examples
Example 1
Explain what a polymer is. [2 marks]
Model answer
A polymer is a very large molecule (1 mark) formed when many small molecules called monomers join together in a repeating chain (1 mark).
Example 2
Explain why polymers are solid at room temperature. [2 marks]
Model answer
Polymer molecules are very large, so the intermolecular forces between the chains are relatively strong (1 mark), and a considerable amount of energy is needed to overcome them (1 mark).
Example 3
Explain why a polymer melts at a lower temperature than diamond. [2 marks]
Model answer
In a polymer only the intermolecular forces between chains need to be overcome (1 mark), whereas in diamond strong covalent bonds throughout the giant structure must be broken, which requires far more energy (1 mark).
Common mistakes
Saying polymers have weak intermolecular forces.
They are relatively strong because the molecules are so large — that is why polymers are solids.
Confusing monomer and polymer.
Monomers are the small units; the polymer is the large molecule they form.
Saying covalent bonds break when a polymer melts.
Only the intermolecular forces between chains are overcome.
Comparing polymers to ionic compounds as equally strong.
Polymer intermolecular forces are much weaker than ionic bonds.
Exam tips
- Use the words monomer and repeating unit in your definition.
- Explain the solid state through large molecules and stronger forces.
- Compare with both simple molecular and giant structures.
- Remember it is still intermolecular forces being overcome.
Key terms
- Polymer
- A very large molecule made from many monomers.
- Monomer
- A small molecule that joins to form a polymer.
- Repeating unit
- The section of a polymer that repeats along the chain.
- Intermolecular force
- The attraction between separate polymer chains.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.