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Polymerisation

Worksheet Overview

QUESTION 1 of 10

Think of the most important things in your life – your phone, your music player, your vacuum cleaner (if you like having a clean bedroom). They will all be made with plastics in them. Plastics really became common in the 1960's. They where a revolution in chemistry – suddenly it was cheap and easy to make basically everything and, unlike wood and paper, plastics did not rot.

We're now more aware of the pollution problems caused by plastics, and need to work hard to solve them, but plastics are still incredibly useful.

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 lots of monomers, you get a polymer. Living things make a lot of polymers naturally; proteins, starch and DNA are all examples of natural polymers.

Plastics have names like polythene, polycarbonate, polyvinyl chloride (PVC). The "poly" part tells you that there are lots of repeating molecules joined together. The second part of the name tells you what the monomer is. So in polythene, we have lots of ethene monomers joined in a chain.

Making polymers

The simplest sort of polymer to understand is called an addition polymer, becuase we just add more and more monomers in a chain, one after the other. 

If we want to make polythene, we need to start with an ethene molecule to make this work. In the diagram below, on the left-hand side, you can see an ethene monomer. If you look in 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.

 

All we do is 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 and you get the idea until the chains are hundreds of bonds long. The final version of the diagram (the one with brackets) is called the displayed formula. The part in brackets repeats, the bonds reaching out link this monomer to its neighbours, and the n at the bottom-right of the brackets tells us that there are many repeats of the monomer.

What controls the properties of the plastic?

Good question – there are two things to think about. One is the monomer used; different monomers make plastics with different properties;

Polymer Properties Uses
Polythene flexible, cheap, electrical insulator plastic bags, insulation for electric wires
Polypropene flexible, strong, tough crates, ropes, plastic furniture
Polyvinyl chloride tough, cheap window frames, water pipes
Polytetrafluoroethene tough, chemically unreactive waterproof clothing, non-stick pans

The other factor is the length of the polymer chains. Longer chains mean that there are more intermolecular forces . More intermolecular forces mean that the resulting plastic is stronger, less flexible and has a higher melting point.

Despite their problems, plastics are still a very useful group of materials. They are made by joining together alkene molecules, which come from crude oil. That's another reason why we need to be careful how we use the planet's fossil fuel reserves.

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 polypropene?

What do we call the process used to make polymers?

Polyfying

Polyfication

Polymerisation

What is special about an Alkene?

They have C-C bonds

They only have C=C double bonds

They have one C=C double bonds.

Which of these compounds is an alkene?

Alkene

Propene

Poly(ethene)

Methane

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

Yes

No

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

Make the chain longer

Make the chain shorter

Increase the number of chains

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

What polymer is good for making ropes?

Which properties make polythene good for making plastic shopping bags?

Flexible

Cheap

Electrical insulator

  • 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
A lot of monomers form a long chain to make a polymer.
  • Question 2

What is the monomer used to make polypropene?

CORRECT ANSWER
propene
EDDIE SAYS
Polymer names start with "poly", then have the name of the monomer- so polypropene is lots of propenes. Sometimes the monomer name is written in brackets, which makes things a bit clearer, so poly(propene).
  • Question 3

What do we call the process used to make polymers?

CORRECT ANSWER
Polymerisation
EDDIE SAYS
Polymerisation is the process used to make polymers. You are making polymers, so poly needs to be in the name.
  • Question 4

What is special about an Alkene?

CORRECT ANSWER
They have one C=C double bonds.
EDDIE SAYS
The spy name of alkenes is 0014; they have double Bonds (sorry...) In alkenes, one of the C-C single bonds is replaced by a double C=C bond.
  • Question 5

Which of these compounds is an alkene?

CORRECT ANSWER
Alkene
Propene
EDDIE SAYS
Alkene and propene are alkenes because they have a double bond between their carbon atoms. In terms of their names, look for "-ene" at the end of the name.
  • Question 6

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

CORRECT ANSWER
No
EDDIE SAYS
Hydrocarbons contain only hydrogen and carbon - that's why they are called hydrocarbons. Hydro for hydrogen and carbon for carbon.
  • Question 7

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

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

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

CORRECT ANSWER
intermolecular
EDDIE SAYS
When we're thinking about covalent molecular structures (like polymers), the bonds between the molecules are the weak ones, which determine the properties of the material.
  • Question 9

What polymer is good for making ropes?

CORRECT ANSWER
polypropene
poly(propene)
EDDIE SAYS
Polypropene is a good polymer to use for ropes, because it is flexible and strong.
  • Question 10

Which properties make polythene good for making plastic shopping bags?

CORRECT ANSWER
Flexible
Cheap
EDDIE SAYS
Polythene isn't very strong- think how often plastic bags break! Bags need to be flexible, and polythene is good for that. The important thing is how cheap polythene is. It's one of the great things about plastics, but it has stopped us thinking how we should reuse plastic materials, which is a problem.
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