Synthetic and naturally occurring polymers

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What Are Polymers?

Polymers are very large molecules with a high relative molecular mass.
They are made by joining together many small molecules called monomers.
Each monomer becomes a repeat unit in the polymer chain.
Monomers are connected to neighbouring units by strong covalent bonds.
Polymerisation reactions usually need high pressure and a catalyst.
Synthetic polymers are manufactured by humans, e.g. plastics, polystyrene cups and nylon.
Natural (biological) polymers are produced by living things, e.g. DNA, proteins, starch and cellulose.

Monomers joining to form a polymer

Addition Polymerisation

Addition polymerisation happens when many monomers join together to form one large polymer molecule only.
It only occurs in monomers that contain a C=C double bond, such as alkenes.
One bond in each C=C breaks, allowing the monomer to bond to the next monomer.
The polymer formed contains single bonds only — no double bond remains in the repeat unit.
The repeat unit has exactly the same atoms as the monomer because no other molecule is formed.
Poly(ethene) (polythene) is made by addition polymerisation of ethene monomers.
Other examples include poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE).
The polymer is named by putting the monomer name in brackets and adding the prefix poly-.

Addition polymerisation of ethene and chloroethene

Drawing Addition Polymers and Their Monomers

To draw the repeat unit from a monomer, change the C=C double bond to a single bond.
Add a bond to each end of the repeat unit — these extension bonds must go outside the brackets.
Write a small subscript n at the bottom right to show a large number of repeat units.
Keep the other groups in the same order as they were around the double bond in the monomer.
To find the monomer from a polymer, identify the repeating unit and change its single bond back to a double bond.
Remove the extension bonds and the subscript n — the n can be placed in front of the monomer.
A common mistake is leaving a double bond in the repeat unit of an addition polymer — don't do this.

Condensation Polymerisation

Condensation polymerisation joins two different monomers together and removes a small molecule, usually water.
The monomers each have two functional groups, one at each end.
The functional groups at the ends of one monomer react with those on the other monomer.
This creates long chains of alternating monomers.
For every new linkage formed, one small molecule (e.g. water) is lost.
This is the key difference from addition polymerisation, which forms the polymer molecule only.
Polyesters are condensation polymers made from a dicarboxylic acid (two -COOH groups) and a diol (two -OH groups).
An example is terylene, made from dicarboxylic acid and diol monomers.

Ester Linkages in Polyesters

Each -COOH group reacts with an -OH group on another monomer.
An ester linkage is formed, with the loss of one water molecule per link.
The water molecule is formed from an -H and an -OH group combining.
The structure of a polyester can be shown using boxes to represent carbon chains.
The bonding sequence is a mirror image at either end of the link, not a simple repetition of the link.

Problems with Polymers

Polymers contain strong covalent bonds, making them unreactive and chemically inert.
They do not easily biodegrade, so micro-organisms cannot break them down.
Landfill disposal takes up valuable land and sites quickly fill up.
Incineration releases a lot of heat energy and produces carbon dioxide, a greenhouse gas.
Burning polymers that contain chlorine, such as PVC, releases toxic hydrogen chloride gas.
Incomplete combustion can produce toxic carbon monoxide.
Recycling requires different polymers to be separated, which is difficult and expensive.

Recycling Polymers: Advantages and Disadvantages

Advantage: recycling is more economically viable than making polymers from scratch.
Advantage: it decreases the use of crude oil, keeping it for other purposes.
Advantage: it reduces greenhouse gas and toxic gas emissions from manufacturing.
Advantage: it reduces the amount of landfill needed and creates employment.
Disadvantage: sorting plastics by type is tedious, labour-intensive and costly.
Disadvantage: production may be limited by what is collected as raw material.
Disadvantage: melting polymers produces toxic gases harmful to plants and animals.
Disadvantage: polymers can only be recycled a limited number of times before losing their properties.

Natural Polymers: DNA

DNA (deoxyribonucleic acid) is a large molecule essential to all life.
It encodes genetic instructions for the development and functioning of organisms and viruses.
DNA is made from four different monomers called nucleotides.
The nucleotides contain bases abbreviated A, T, C and G.
The nucleotides form two strands that intertwine to give the double helix shape.
The bases on the two chains pair up in specific sequences, forming cross links that hold the strands together.
Genetic information is stored in the order of the bases, which acts as a code for the organism's genes.

Natural Polymers: Proteins, Starch and Cellulose

Proteins are condensation polymers made from amino acid monomers.
Amino acids contain an amine (-NH₂) group and a carboxylic acid (-COOH) group.
Amino acids join by peptide links; one water molecule is lost per peptide link.
Long chains of amino acids are called polypeptides; proteins are one or more polypeptide chains.
Most proteins contain at least 20 different amino acids, and their order determines structure and properties.
Examples of proteins and their functions: haemoglobin transports oxygen, antibodies protect against viruses and bacteria, enzymes are biological catalysts.
Starch and cellulose are carbohydrates made from sugar monomers.
Starch stores energy; cellulose is a stiff polymer used in plant cell walls for support.

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1.Which small molecules join together in large numbers to form a polymer?
Easy
- AMonomers
- BRepeat units
- CNucleotides
- DAmino acids
2.In an addition polymer, the repeating unit contains a carbon–carbon double bond.
Easy
True or false?
3.Ethene can undergo polymerisation. What type of polymer does ethene form?
Easy
- ACondensation
- BAddition
- CSubstitution
- DNeutralisation
4.PVC, poly(chloroethene), is a polymer formed from chloroethene. What type of polymer is poly(chloroethene)?
Easy
- AAddition
- BCondensation
- CSubstitution
- DNatural
5.What type of bond is formed between the atoms in poly(chloroethene)?
Easy
- AIonic
- BMetallic
- CCovalent
- DElectrostatic
6.Which of the following statements about addition polymerisation are correct? (select all that apply)
Medium
- AIt forms the polymer molecule only.
- BIt forms a small molecule such as water.
- CIt occurs in monomers that contain C=C bonds.
- DThe polymer contains only single bonds.
- EIt requires two different monomers.
7.Which of these is the correct name for the polymer formed from propene?
Easy
- APoly(propane)
- BPoly(propene)
- CPropene polymer
- DPoly(ethene)
8.PTFE, poly(tetrafluoroethene), is a polymer which is resistant to high temperatures. Name the monomer that PTFE is formed from.
Easy
- AEthene
- BChloroethene
- CTetrafluoroethene
- DPropene

Plus de questions

9.Here are five statements about PTFE. Which two statements are correct? (select all that apply)
Medium
- AIt is saturated
- BIt contains ionic bonds
- CIt is an addition polymer
- DIt is used to make plastic bags
- EIt is a hydrocarbon
10.Which of the following is not true about DNA?
Medium
- ADNA is made from four different monomers.
- BDNA is a polymer.
- CDNA is made from nucleotides.
- DThe monomers that form DNA are amino acids.
11.Draw one line from each naturally occurring polymer to the monomer it is formed from.
Medium
- Protein
- Starch
- Cellulose
- Amino acids
- Sugar
12.Which statements are correct about the structure of DNA? (select all that apply)
Medium
- AIt consists of three polymer chains.
- BIt has bases A, C, G and T.
- CIt has a double helix structure.
- DIt is formed from the monomer glucose.
13.What type of polymerisation are proteins formed by?
Medium
- AAddition
- BCondensation
- CSubstitution
- DNeutralisation
14.A polyester can be formed from two monomers. When these two monomers produce a polyester, another small molecule is formed. Which small molecule is formed?
Medium
- AWater
- BHydrogen
- CCarbon dioxide
- DOxygen
15.What kind of polymer is a polyester formed by?
Medium
- AAddition
- BCondensation
- CSubstitution
- DNatural
16.Addition polymerisation forms one water molecule per linkage.
Easy
True or false?
17.Some polymers are polyesters. What type of reaction takes place when polyesters are formed?
Medium
- AAddition
- BCondensation
- CNeutralisation
- DPrecipitation
18.Which of the following statements about addition and condensation polymerisation is correct?
Medium
- AAddition polymerisation forms a small molecule as well as the polymer.
- BCondensation polymerisation forms only the polymer.
- CAddition polymerisation forms only the polymer, while condensation polymerisation also forms a small molecule.
- DBoth addition and condensation polymerisation form water.
19.Which of the following is a correct repeat unit for the polymer formed from ethanediol and butanedioic acid?
Medium
- AA structure with an ester linkage and no loss of water
- BA structure with an ester linkage formed by condensation with loss of water
- CA structure with a C=C double bond
- DA structure with an amide linkage
20.Which of the following are true about condensation polymerisation? (select all that apply)
Hard
- AIt involves monomers with two functional groups.
- BIt produces a small molecule such as water.
- CIt requires monomers with C=C bonds.
- DIt can form polyesters and polyamides.
- EThe polymer contains only the atoms of the monomers.
21.Why are many polymers not biodegradable?
Medium
- AThey contain weak ionic bonds that micro-organisms can break.
- BThey are made of strong covalent bonds and are chemically inert.
- CThey dissolve easily in water.
- DThey are made from natural monomers.
22.Polymers that contain chlorine, such as PVC, release toxic hydrogen chloride gas when burned.
Easy
True or false?
23.Which of the following is a disadvantage of disposing of polymers in landfill sites?
Medium
- AThey biodegrade too quickly and cause land to collapse.
- BThey are non-biodegradable and take up valuable land.
- CThey release toxic gases into the air.
- DThey dissolve and contaminate water supplies.
24.Which of the following is an advantage of recycling polymers?
Medium
- AIt increases the use of crude oil.
- BIt reduces the amount of landfill waste and saves raw materials.
- CIt produces more toxic gases than incineration.
- DIt requires no separation of different polymers.
25.Which of the following is a naturally occurring polymer?
Medium
- APoly(ethene)
- BPVC
- CProtein
- DNylon
26.Which of the following are naturally occurring polymers? (select all that apply)
Medium
- AStarch
- BCellulose
- CPoly(propene)
- DDNA
- ENylon
27.Which of the following is the correct monomer for starch?
Medium
- AAmino acid
- BSugar
- CNucleotide
- DFatty acid
28.DNA is made from four different monomers called nucleotides.
Easy
True or false?
29.Which of the following statements about the structure of DNA is correct?
Medium
- AIt is a single polymer chain.
- BIt is made of three polymer chains.
- CIt consists of two polymer chains in a double helix.
- DIt is made from glucose monomers.
30.Which of the following is a correct difference between addition and condensation polymerisation?
Medium
- AAddition polymerisation releases water; condensation does not.
- BCondensation polymerisation releases water; addition does not.
- CBoth release water.
- DNeither releases water.
31.Which of the following is a correct repeat unit for an addition polymer?
Medium
- AA structure with a double bond and brackets.
- BA structure with a single bond and extension bonds outside brackets.
- CA structure with an ester linkage.
- DA structure with an amide linkage.
32.Which of the following is a common misconception about polymers?
Medium
- AAll polymers are synthetic.
- BSome polymers are natural.
- CPolymers are large molecules.
- DPolymers are made from monomers.
33.A polymer has the repeat unit shown. Which of the following is the correct monomer?
Hard
- AA molecule with a C=C double bond and the same atoms as the repeat unit.
- BA molecule with an ester linkage.
- CA molecule with an amide linkage.
- DA molecule with a single bond only.
34.Which of the following statements about the disposal of polymers are correct? (select all that apply)
Medium
- ALandfill sites take up valuable land because polymers are non-biodegradable.
- BBurning polymers always produces only harmless gases.
- CIncomplete combustion of polymers can produce toxic carbon monoxide.
- DRecycling polymers is always easy and cheap.
- EBurning polymers releases carbon dioxide, a greenhouse gas.
35.Which of the following is a disadvantage of recycling polymers?
Medium
- AIt reduces the amount of landfill waste.
- BIt saves crude oil.
- CSorting different polymers is difficult and expensive.
- DIt reduces greenhouse gas emissions.
36.Which of the following is a correct statement about the manufacture of poly(ethene)?
Medium
- AIt is made from ethene obtained by cracking fractions from crude oil.
- BIt is made from glucose.
- CIt is made by condensation polymerisation.
- DIt is a natural polymer.
37.Which of the following is a correct description of the structure of a protein?
Hard
- AA polymer of nucleotides joined by glycosidic linkages.
- BA polymer of amino acids joined by peptide links.
- CA polymer of sugars joined by ester linkages.
- DA polymer of alkenes joined by single bonds.
38.Which of the following is a correct statement about the monomers of naturally occurring polymers?
Hard
- AProteins are made from sugar monomers.
- BStarch and cellulose are made from amino acid monomers.
- CProteins are made from amino acids, and starch and cellulose are made from sugar monomers.
- DDNA is made from glucose monomers.
39.Which of the following is a correct difference between addition and condensation polymers in terms of their repeat units?
Hard
- AAddition polymers have repeat units with the same atoms as the monomer; condensation polymers have repeat units with fewer atoms than the monomers.
- BAddition polymers have repeat units with fewer atoms than the monomer; condensation polymers have the same atoms as the monomers.
- CBoth have repeat units with the same atoms as the monomers.
- DBoth have repeat units with fewer atoms than the monomers.
40.A student draws a repeat unit for an addition polymer but leaves a double bond in the structure. What is wrong with this?
Challenge
- AThe double bond should be changed to a single bond.
- BThe double bond should be changed to a triple bond.
- CThe double bond should be removed completely.
- DNothing is wrong; addition polymers contain double bonds.
41.Complete the sentence about addition polymerisation.
Easy
During polymerisation, many ethene ____ join together to form the large molecule, poly(ethene).
42.Name the polymer formed by the addition polymerisation of ethene.
Easy
43.Complete the sentence about the structure of DNA.
Easy
DNA consists of four different monomers called ____, and it has a ____ helix structure.
44.Complete the sentence about condensation polymerisation.
Medium
Condensation polymers are formed when two different monomers are linked together with the removal of a small molecule, usually ____.
45.Name the three elements found in glucose.
Easy
Glucose contains the elements ____, ____ and ____.
46.Explain some of the problems associated with the manufacture and disposal of poly(ethene).
Hard
47.Explain why poly(chloroethene) is a suitable material for surrounding the copper in electrical cables.
Hard
48.Give two advantages of recycling PTFE.
Medium
49.Describe how the structure of DNA is related to its function.
Medium
50.Explain the basic principles of condensation polymerisation by reference to the functional groups in the monomers and the repeating units in the polymers.
Hard

Cartes mémo

What is a polymer?

A large molecule of high relative molecular mass made by linking together many smaller molecules called monomers.

What is a monomer?

A small molecule that can join with many others to form a polymer.

What type of bond connects monomers together in a polymer chain?

Covalent bonds.

What conditions are usually needed for polymerisation reactions?

High pressures and a catalyst.

What is addition polymerisation?

The joining together of many monomers containing C=C bonds to form a polymer, with no other molecule formed.

Which functional group must a monomer contain for addition polymerisation to occur?

A carbon-carbon double bond (C=C).

What happens to the C=C bond during addition polymerisation?

One of the bonds in each C=C bond breaks and forms a bond with the adjacent monomer, so the polymer contains single bonds only.

Name the polymer formed by the addition polymerisation of ethene.

Poly(ethene), commonly called polythene.

How is the name of an addition polymer derived from its monomer?

Put the monomer name in brackets and add the prefix poly-, e.g. propene → poly(propene).

What is the monomer used to make poly(chloroethene) (PVC)?

Chloroethene.

What is the monomer used to make PTFE, poly(tetrafluoroethene)?

Tetrafluoroethene.

When drawing the repeat unit of an addition polymer, what must you do to the double bond?

Change the double bond in the monomer to a single bond in the repeat unit.

What are extension (continuation) bonds in a repeat unit?

Bonds on either side of the repeat unit that extend outside the brackets, showing the polymer chain continues.

What does the subscript n represent in a polymer repeat unit?

A large number of repeat units joined together.

How do you deduce the monomer from a given addition polymer repeat unit?

Identify the repeating unit, change the single bond back to a double bond, and remove the extension bonds and the subscript n.

What is condensation polymerisation?

When two different monomers with two functional groups each join together with the removal of a small molecule, usually water.

What is the key difference between addition and condensation polymerisation?

Addition polymerisation forms only the polymer molecule; condensation polymerisation also forms one small molecule (usually water) per linkage.

What type of monomers react to form a polyester?

A dicarboxylic acid (with -COOH groups at both ends) and a diol (with -OH groups at both ends).

What linkage is formed in a polyester?

An ester linkage.

What small molecule is lost for every ester linkage formed in a polyester?

Water.

Name the polyester made from dicarboxylic acid and diol monomers.

Terylene.

What functional groups are present in an amino acid?

An amine group (-NH2) and a carboxylic acid group (-COOH).

What type of polymerisation do amino acids undergo to form proteins?

Condensation polymerisation.

What is the name of the bond that links amino acids together in a protein?

A peptide bond (or peptide link).

What are proteins made from?

Amino acid monomers joined together by peptide bonds.

What is DNA and what is it made from?

Deoxyribonucleic acid, a large molecule essential for life, made from four different monomers called nucleotides.

What are the four bases in DNA abbreviated to?

A, T, C and G.

What is the structure of DNA?

Two polymer chains (strands) that intertwine to form a double helix.

What monomer is starch made from?

Sugar.

What monomer is cellulose made from?

Sugar.

Name three naturally occurring polymers.

Proteins, starch and cellulose.

Why are many polymers not biodegradable?

They are made of strong covalent bonds, making them unreactive and chemically inert so microorganisms cannot break them down.

What is a problem with disposing of polymers in landfill sites?

They are non-biodegradable so they take up valuable land and sites quickly fill up.

What toxic gas is released when polymers containing chlorine, such as PVC, are burned?

Hydrogen chloride.

What gas is produced by incomplete combustion of polymers and is toxic?

Carbon monoxide.

Give two advantages of recycling polymers.

It decreases the use of crude oil and reduces the amount of landfill waste; it also reduces greenhouse gas emissions and creates employment.

Give two disadvantages of recycling polymers.

Sorting plastics by type is labour intensive and costly; melting polymers produces toxic gases and they can only be recycled a limited number of times.

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