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Understand Polymerisation

Worksheet Overview

QUESTION 1 of 10

Think of the most important things in your life – your phone, your tablet, your vacuum cleaner (if you like having a clean bedroom). They will all be made with plastics in them. The making of plastics was a revolution in chemistry – suddenly it was cheap and easy to make basically everything, and humans embraced plastics like the new future. It is easy to be critical of the overuse of plastics now, after all we know how much harm they can do to the environment, but back in the day, they were super.

 

The manufacture of plastics comes from oil. Polymers are very big molecules with long chains and they are made from many small molecules called monomersPoly- means many, mono- means one. When you stick together loads of monomers, you get a polymer – most of the time this is a plastic.

Ever heard of the plastic polypropane? Well, you get the name of the polymer if you add the prefix poly- before the name of the monomer. For example, poly(propane) which is used to make ropes, is made of lots of propane molecules joined in a long chain.


So, there are a few words you need to know when talking about polymers. Alkene is the big one here. In the diagram below, on the left-hand side you can see an alkene. If you look between the two carbons, you can see that there is a double bond (two lines). This is what makes an alkene. If it has a carbon-carbon double bond, then it is ripe for being made into a plastic.

 

An image showing how an alkene is made into a long chain polymer.

 

So, how do we make a monomer into a polymer?

 

We need a chemical reaction that breaks apart one of the double bonds in the alkene. When this is broken, it is freed up to bond with another alkene. This process means that one alkene can bond to make a chain of two, and then three and then four, you get the idea, until the chains are hundreds of bonds long.

 

“But I know that there are loads of different types of plastics – what makes them different?”

 

Good question – it’s all about the length of the chains. Longer chains mean that there are more intermolecular forces, and more intermolecular forces mean a harder plastic. Let’s look at a table to illustrate this.

 

Property of plastic Long chains Short chains
Strength Tend to be strong as there are a lot of intermolecular forces.  Tend to be weak as there are not a lot of intermolecular forces. 
Flexibility Tend to be more flexible as there are fewer branches on the polymer chains stopping them from flowing over each other.  Tend to be less flexible as there tend to be more branches on the chains that get caught up in each other and stop the flow. 
Hardness Tend to be less hard and the chains can slide over each other.  Tend to be harder as the chains cannot slide as easily. 
Melting point High melting point as there are more intermolecular forces between long chains Low melting point as there are fewer intermolecular forces between long chains

 

Let's move on to try some questions on this subject now.

Is the following sentence true or false?

 

A lot of polymers form a long chain to make a monomer.

True

False

What is the monomer used to make poly(ethylene)?

What do we call the process used to make polymers?

Polyfying

Polyfication

Polymerisation

What do we call the forces that hold the polymer chains to one another? 

What is special about an alkene?

Carbon-carbon double bond

Carbon single bond

Hydrogen-hydrogen double bond

Hydrogen single bond

Which of the compounds below are alkenes?

Alkene

Propene

Poly(ethene)

Methane

What do you need to do to the polymer chain to make it harder? 

Make the chain longer

Make the chain shorter

Make it with a different monomer

A compound contains hydrogen, carbon and nitrogen. Is it a hydrocarbon?

Yes

No

The length of the polymer chain can affect the properties of the plastic made. 

 

What other thing will affect the properties of the final material?

Yes

No

What do we call polymers that dissolve and do not pollute the environment?

  • Question 1

Is the following sentence true or false?

 

A lot of polymers form a long chain to make a monomer.

CORRECT ANSWER
False
EDDIE SAYS
Now don't get muddled by your monomers and your polymers!! Remember that the prefix 'mono' means one and 'poly' means many. This means that you would need a lot of monomers to form a long chain to make a polymer - not the other way round!
  • Question 2

What is the monomer used to make poly(ethylene)?

CORRECT ANSWER
ethylene
EDDIE SAYS
Well done if you managed to spell this one correctly - watch out for that 'y'. Ethylene is the monomer used to make poly(ethylene). Remember the naming convention - where the monomer is always in brackets after the prefix 'poly'.
  • Question 3

What do we call the process used to make polymers?

CORRECT ANSWER
Polymerisation
EDDIE SAYS
What a bunch of tricky words - at least you didn't have to spell it! Polymerisation is the process used to make polymers - you are making polymers, so 'poly' needs to be in the name.
  • Question 4

What do we call the forces that hold the polymer chains to one another? 

CORRECT ANSWER
intermolecular
EDDIE SAYS
It's always tricky when you've got to write an answer without any options to choose from! How did you get on with this one? The name of the forces that we need to change when we are looking at all chemical structures is intermolecular - the force between the molecules. Phew - that was quite a challenging set of questions with lots of words to remember. Hopefully, you feel a bit more confident about this topic now, but if you are still finding it tricky, why not reread the Introduction and then try the questions again.
  • Question 5

What is special about an alkene?

CORRECT ANSWER
Carbon-carbon double bond
EDDIE SAYS
There are two 007's in that alkene - it has a double bond... Sorry... An alkene has a double carbon bond which can be broken to enable the creation of long chains of alkenes.
  • Question 6

Which of the compounds below are alkenes?

CORRECT ANSWER
Alkene
Propene
EDDIE SAYS
This was a hard question so don't worry if you didn't get it correct. Alkene and propene are alkenes because they have a double bond between their carbon atoms. Methane is a monomer and polyethene is a polymer made from loads of ethene monomers.
  • Question 7

What do you need to do to the polymer chain to make it harder? 

CORRECT ANSWER
Make the chain longer
EDDIE SAYS
In order to make the plastic harder, you need to increase the polymer chain length which will increase the intermolecular forces.
  • Question 8

A compound contains hydrogen, carbon and nitrogen. Is it a hydrocarbon?

CORRECT ANSWER
No
EDDIE SAYS
Did you get it? Hydrocarbons contain only hydrogen and carbon - that's why they are called hydrocarbons! Hydro for hydrogen and carbon for carbon. The compound mentioned above also contains nitrogen so it can't be a hydrocarbon.
  • Question 9

The length of the polymer chain can affect the properties of the plastic made. 

 

What other thing will affect the properties of the final material?

CORRECT ANSWER
EDDIE SAYS
Chain length and the number of branches both affect how easily polymer chains are able to pull over each other. This is because longer chains and fewer branches both increase the intermolecular forces in the polymer.
  • Question 10

What do we call polymers that dissolve and do not pollute the environment?

CORRECT ANSWER
Biodegradable polymers
Biodegradable polymer
Biodegradable
EDDIE SAYS
Biodegradable polymers dissolve and do not pollute the environment so manufacturers are encouraged to produce this type of polymer nowadays.
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