New
New
Year 9

Structure of polymers

I can give examples of polymers and explain how the properties of polymers depend on their structure.

New
New
Year 9

Structure of polymers

I can give examples of polymers and explain how the properties of polymers depend on their structure.

Lesson details

Key learning points

  1. Polymers are made from small molecules called monomers that join together to form very long chains of atoms.
  2. Some polymers have high melting points because their molecules are hard to separate.
  3. Polymers can be made synthetically, but some also exist naturally.
  4. A plasticiser added to a polymer gets between polymer molecules and allows them to move over each other more easily.
  5. Cross-links between polymer molecules can make a polymer harder and less flexible.

Common misconception

Students often think that intermolecular forces exist within a molecule, unaware of the significant difference in strength between chemical bonds within atoms and the forces between molecules.

Help students to make the link between the structure of the polymer and its property by using models. Point out where the intermolecular forces occur and compare this to where the chemical bonds are.

Keywords

  • Polymer - Long-chained molecules formed by joining together monomers.

  • Forces of attraction - A pulling force that keeps particles close together.

  • Synthetic - A product that is manufactured from natural resources.

  • Plasticiser - A substance that is added to a polymer to increase its flexibility.

  • Cross-link - A chemical bond between different chains of atoms in a polymer.

Show students a range of natural and synthetic polymers, such as rubber with and without cross links and PVC with and without plasticisers. Ask them to predict what would happen to the properties of a polymer if a plasticiser or cross-link was added. Slime could be made from PVA glue and borax.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Which of the following three properties make polymers useful for making plastic water bottles?
brittle
Correct answer: durable
Correct answer: flexible
insulator
Correct answer: lightweight
Q2.
Plastics are polymers, but not all polymers are plastics. Which of the following materials are classified as polymers?
brass
carbon fibre
glass
Correct answer: rubber
steel
Q3.
Models are used in science to test ideas without facing practical or ethical issues. However, they have , such as only representing one aspect of a concept rather than the whole.
Correct Answer: limitations, drawbacks, weaknesses
Q4.
Match the following key terms to their definition.
Correct Answer:atom,particles that make up chemical elements

particles that make up chemical elements

Correct Answer:chemical bond,a strong force that holds atoms together in a compound

a strong force that holds atoms together in a compound

Correct Answer:chemical compound,a substance where two or more different elements are chemically bonded

a substance where two or more different elements are chemically bonded

Correct Answer:element,a substance made up of only one type of atom

a substance made up of only one type of atom

Correct Answer:molecule,made up of two or more atoms chemically bonded (usually non–metals)

made up of two or more atoms chemically bonded (usually non–metals)

Q5.
Which of the following properties of rubber makes it useful for making rubber bands?
brittle
durable
Correct answer: flexible
insulator
lightweight
Q6.
Consider ice, water, and water vapour. The atoms and molecules are held together differently and with varying strengths. What happens at the boiling point when water turns to water vapour?
the atoms move around each other in the water molecules
the chemical bonds in the water molecules become weaker
Correct answer: the water molecules have enough energy to overcome the forces between them
the water molecules move around each other more in the liquid

6 Questions

Q1.
Match the following key terms to their definition.
Correct Answer:chemical bond,a strong force that holds atoms together in a compound

a strong force that holds atoms together in a compound

Correct Answer:cross–link,a chemical bond between atoms in different polymer chains

a chemical bond between atoms in different polymer chains

Correct Answer:forces of attraction,a pulling force that keeps particles close together

a pulling force that keeps particles close together

Correct Answer:plasticiser,a substance that is added to a polymer to increase its flexibility

a substance that is added to a polymer to increase its flexibility

Q2.
Materials can be natural or synthetic. Natural means they occur in nature. Synthetic means they are .
Correct Answer: human-made, man-made, manufactured, artificial
Q3.
Polymers can be represented with models. Which list correctly describes the image with three polymer models, from left to right?
An image in a quiz
branched polymer; polymer with plasticiser; cross–linked polymer
branched polymer; cross–linked polymer; polymer with plasticiser
Correct answer: cross–linked polymer; polymer with plasticiser; branched polymer
cross–linked polymer; branched polymer; polymer with plasticiser
polymer with plasticiser; cross–linked polymer; branched polymer
Q4.
Match the following key terms to their description.
Correct Answer:cellulose,natural; carbohydrate found in plant cell walls

natural; carbohydrate found in plant cell walls

Correct Answer:DNA,natural; nucleic acid involved in carrying genetic information

natural; nucleic acid involved in carrying genetic information

Correct Answer:HDPE,synthetic; high density poly(ethene) used for plastic bottles

synthetic; high density poly(ethene) used for plastic bottles

Correct Answer:LDPE,synthetic; low density poly(ethene) used for plastic bags

synthetic; low density poly(ethene) used for plastic bags

Correct Answer:PVC,synthetic; poly(vinyl chloride) used for sockets, switches and wellies

synthetic; poly(vinyl chloride) used for sockets, switches and wellies

Correct Answer:wool,natural; protein fibre often made by sheep

natural; protein fibre often made by sheep

Q5.
Cross–links in polymers make it harder for polymer molecules to slide past each other. in between polymer chains push the long molecules apart so that forces of attraction are weakened.
Correct Answer: plasticisers, plasticiser
Q6.
A chemical bond is a strong force that holds atoms together in a compound. A chemical bond takes a lot of energy to overcome and break. Which of the following statements are correct?
In polymers, forces of attraction are the same as chemical bonds.
Correct answer: In polymers, forces of attraction are weaker than cross–links.
Correct answer: In polymers, forces of attraction are weakened by plasticisers.
Correct answer: In polymers, forces of attraction are weakened by branches.