The Polymer Workshop

Joining small into large

A polymer is a very long molecule built from many small repeating units called monomers joined together. Plastics such as polyethene are polymers, and so are natural substances such as proteins and starch. There are two ways monomers join. In one, many identical units with a carbon-carbon double bond open up and link into a chain with nothing left over. In the other, two different units join and give off a small molecule such as water. This module teaches both, plus the polymers that occur in nature.

Polymer words

Learn these before you sort any example. The exam wants you to tell the two ways of joining apart precisely.

Addition against condensation

These two ways of making a polymer are the ones learners mix up. The differences are the number of monomer types and whether a small molecule is given off.

How to tell them apart

To tell the two ways of joining apart, ask two questions. How many kinds of small unit are joining, and is anything given off? If one kind of unit with a double bond links up and nothing else is produced, it is the first way. If two different units join and a small molecule such as water comes off, it is the second way. Also remember that some long-chain molecules are not made in a factory at all but occur in living things.

Match the term to its meaning

What is addition polymerisation?

Ethene molecules join into a long chain called polyethene. Which statement describes this?

• Addition polymerisation, because one monomer joins with no by-product.
• Condensation polymerisation, because water is released.
• Cracking, because a big molecule is broken up.
• Neutralisation, because an acid meets a base.

True of addition polymers?

Select the TWO statements that are true of addition polymerisation.

• It uses one type of monomer
• It makes no by-product
• It releases water each time units join
• It always needs two different monomers

Count the carbon atoms

Ethene has the formula C2H4, so each ethene monomer contains 2 carbon atoms. A short polyethene chain is made from 100 ethene monomers joined together. Multiply the number of monomers by the carbons in each to find the total number of carbon atoms. What is the answer?

Order how an addition polymer forms

Put the steps of addition polymerisation in order, earliest first.

• Many ethene monomers are brought together
• The carbon-carbon double bonds open up
• The monomers join end to end
• A long polyethene chain is formed

Complete the polymer facts

A small unit that joins with others is a _____, and the long molecule they build is a _____. When one type of unit with a double bond joins with nothing left over, this is _____ polymerisation. When two different units join and release a small molecule such as water, this is _____ polymerisation.

Match the polymer to what it is

Spot the true polymer facts

Tap the TWO statements that are true about polymers.

• Addition polymerisation makes no by-product
• DNA is a naturally occurring polymer
• Addition polymerisation releases water each time
• No polymers occur in nature

Classify the polymer

Read each case and choose the best answer.

• Many identical monomers, each with a carbon-carbon double bond, join into a long chain and nothing else is produced. Which kind of polymerisation is this?
• Two different monomers join together and a small molecule of water is given off each time. Which kind of polymerisation is this?
• A long molecule found in living cells stores genetic information and is built from units called nucleotides. What is it?

Explain polymers

Explain how polymers are made and how addition and condensation polymerisation differ, and give an example of a naturally occurring polymer.

• Explain what a monomer and a polymer are
• Explain what happens in addition polymerisation and why there is no by-product
• Explain how condensation polymerisation differs from addition
• Name one naturally occurring polymer and what it is built from