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A polymer is a substance with very large molecules made from many repeating units, called monomers. Free notes with key terms and 13 questions answered.
Structure and Properties of Polymers is part of How bonding and structure are related to the properties of substances in GCSE AQA Higher Chemistry.
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A polymer is a substance with very large molecules made from many repeating units, called monomers. Free notes with key terms and 13 questions answered.
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Use this lesson to stay inside How bonding and structure are related to the properties of substances while connecting the detail back to the wider Topic 2: Bonding, structure, and the properties of matter topic.
Read the core explanations from Structure and Properties of Polymers before testing yourself from memory.
Think of a polymer like a massive chain made from thousands of identical links. Each link is a small molecule called a monomer, but when they join together, they create something completely different.
The plastic bag in your kitchen, the nylon in your clothes, even the DNA in your cells - they're all polymers. What makes them special isn't just their size, but how their structure gives them unique properties.
Here's the key insight: polymers have two completely different types of forces holding them together. Understanding both is crucial for explaining their properties.
Picture a bowl of cooked spaghetti. Each strand of spaghetti represents one polymer molecule - very long and made of many units joined together. The forces within each strand are different from the forces between the strands.
The covalent bonds along each polymer chain are very strong, as covalent bonds generally are. But between the polymer chains, the forces are much weaker, though still stronger than in small molecules.
Small molecules like water or methane are liquids or gases at room temperature because their intermolecular forces are weak. But polymers are different - they're solids. Here's why.
Polymer molecules are enormous compared to simple molecules. A single polyethene molecule might contain 50,000 carbon atoms in one continuous chain. This massive size creates much stronger intermolecular forces between polymer molecules.
Think of it like Velcro - two small pieces don't stick strongly, but two large pieces create a powerful bond because there are many more contact points. Polymer molecules have thousands of contact points with their neighbours.
Exam questions often show you diagrams and ask you to identify polymers. There are three key features to look for that scream 'polymer'.
First, look for repeating units. Polymers are made from the same small unit repeated many times. Second, check for very long chains - polymer molecules extend far beyond what you can show in a diagram. Third, spot the continuation marks (usually dots or brackets with 'n') showing the pattern continues.
Worked example: Identifying a Polymer from a Structural Diagram
Look at this structure: -CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-... What evidence shows this is a polymer?
Answer: This is polyethene - the repeating -CH₂- units and continuation marks confirm it's a polymer
**Trap**: Many students think polymers must have complex structures. Actually, some of the most common polymers like polyethene have very simple repeating units.
To really understand polymers, you need to see how they compare to other types of substances. The key is understanding which forces break when the substance melts or dissolves.
In ionic compounds like salt, melting breaks the electrostatic attractions between ions in the lattice. In simple molecular substances like water, melting breaks intermolecular forces but leaves molecules intact. In polymers, melting breaks intermolecular forces between polymer chains.
This explains why polymers have moderate melting points - higher than simple molecules (stronger intermolecular forces) but lower than ionic compounds (no ionic bonds to break).
Polymer questions appear regularly in GCSE exams, and there are predictable mistakes that cost students marks. Here's how to avoid them and pick up every available mark.
**Common Exam Mistake**: Students often say polymers are solids because they have 'strong bonds'. This is too vague - you must specify that it's the intermolecular forces (not covalent bonds) that determine the solid state.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-24.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
A polymer is a substance with very large molecules made from many repeating units, called monomers, joined by strong covalent bonds. Examples include polyethene, nylon and starch.
A monomer is a small molecule that acts as a single repeating unit of a polymer. Many monomers join together by strong covalent bonds to make a very long polymer chain; for example, ethene monomers (CH₂=CH₂) join together to make polyethene.
Polyethene, nylon and starch are examples of polymers. Each is a substance with very large molecules made from many repeating units, called monomers, joined by strong covalent bonds. Other examples include plastic bags, the nylon in clothes and even the DNA in cells.
Polymers are solid at room temperature because their very large molecules have relatively strong intermolecular forces between them. Polymer molecules are enormous, with thousands of contact points with their neighbours, so the forces between chains are stronger than in small molecules.
The repeating unit of polyethene is -CH₂-, in which each carbon is bonded to two other carbons and two hydrogens. This unit repeats along a very long chain, and polyethene is made from ethene monomers (CH₂=CH₂) joining together.
A polymer can be recognised from a diagram by three features: a repeating unit, a very long chain, and continuation marks such as dots or brackets with n showing the pattern continues. For example, repeating -CH₂- units show a structure is polyethene.
When a polymer melts, the intermolecular forces between polymer chains are broken, while the strong covalent bonds along each chain stay intact. This gives polymers moderate melting points, higher than simple molecules but lower than ionic compounds.
In polymers, intramolecular forces are the strong covalent bonds that hold atoms together within a polymer molecule, while intermolecular forces are the relatively weak forces of attraction between separate polymer molecules. The intermolecular forces determine many physical properties.
Polymers have higher melting points than small molecules because their enormous molecules have much stronger intermolecular forces between them. A polymer chain has thousands of contact points with its neighbours, so more energy is needed to separate the chains than to separate small molecules like water or methane.
Polymers have lower melting points than ionic compounds because melting a polymer only breaks the intermolecular forces between polymer chains, with no ionic bonds to break. Melting an ionic compound like salt breaks the strong electrostatic attractions between ions in the lattice, which needs more energy.
The n in a polymer diagram is a continuation mark showing that the repeating unit is repeated many times. Polymer molecules are far too long to draw in full, so dots or brackets with n show that the pattern continues for thousands of units.
A single polyethene molecule might contain 50,000 carbon atoms in one continuous chain. This enormous size gives polymer molecules thousands of contact points with their neighbours, creating much stronger intermolecular forces than in small molecules and making polyethene a solid at room temperature.
Polymers do not need complex structures: some of the most common, such as polyethene, have very simple repeating units like -CH₂-. What makes a substance a polymer is many repeating units joined into very long chains, not a complex unit.