Polymers (Cambridge O Level Chemistry)

Alkenes are unsaturated hydrocarbons. They show structural isomerism. Alkenes take part in addition reactions and form polymers.

Ethene reacts with each of the following. Give the name and structural formula of each product.

Islay is an island off the west coast of Scotland. The main industry on the island is making ethanol from barley.

Barley contains the complex carbohydrate, starch. Enzymes catalyse the hydrolysis of starch to a solution of glucose.

Alkenes polymerise by addition.

Lactic acid can be made from corn starch.

lactic acid

It polymerises to form the polymer, polylactic acid (PLA ) which is biodegradable.

Suggest two advantages that PLA has compared with a polymer made from petroleum.

The structure of PLA is given below.

[1]

[2]

[2]

When lactic acid is heated, acrylic acid is formed.

[1]

[3]

[2]

Synthetic polymers are disposed of in landfill sites and by burning.

State two uses of synthetic polymers.

The structural formulae of two synthetic polymers are given below.

Explain the difference between addition and condensation polymers. Classify A and B as either addition or condensation polymers.

Polymers are made by the polymerisation of simple molecules called monomers.

Many polymers are non-biodegradable.

Many monomer molecules react together to form one molecule of a polymer. This reaction is called polymerisation.

The structural formula of the polymer, poly(chloroethene), is given below. This polymer is also known as PVC.

The carbohydrate, glucose, polymerises to form the more complex carbohydrate starch.

If glucose is represented by

then the structural formula of starch is as drawn below.

How does the polymerisation of glucose differ from that of an alkene such as phenylethene?

Domestic rubbish is disposed of in landfi ll sites. Rubbish could include the following items.

Explain why aluminium, a reactive metal, takes so long to corrode.

Both paper and cotton are complex carbohydrates. They can be hydrolysed to simple sugars such as glucose.

The formula of glucose can be represented as:

Draw the structural formula of a complex carbohydrate, such as cotton.

Include at least two glucose units.

Separate: Chemistry Only

Plastics are polymers. They are formed from their monomers by polymerisation.

Two methods for the disposal of waste plastics are

• burning
• recycling.

Describe one advantage and one disadvantage of each method.

burning ..............................................................................................................................

recycling ...........................................................................................................................

Extended Only

There are two types of polymerisation - addition and condensation.

Explain the difference between them.

Poly(dichloroethene) is used to package food. Draw its structure. The structural formula of dichloroethene is shown below.

Enzymes are biological catalysts. They are used both in research laboratories and in industry.

Enzymes called proteases can hydrolyse proteins to amino acids. The amino acids can be separated and identified by chromatography. The diagram below shows a typical chromatogram.

The R_f value of a sample = 

• glutamic acid = 0.4
• glycine = 0.5
• alanine = 0.7
• leucine = 0.9

Fermentation can be carried out in the apparatus drawn below. After a few days the reaction stops. It has produced a 12% aqueous solution of ethanol.

Alkenes are unsaturated hydrocarbons. They undergo addition reactions.

Two of the methods of making alkenes are cracking and the thermal decomposition of chloroalkanes.

The following alkenes are isomers.

Give the name of the product when but-1-ene reacts with each of the following.

steam .........................................................

hydrogen ....................................................

bromine ......................................................

Alkenes can polymerise.

Alkenes are unsaturated hydrocarbons. They show structural isomerism. Alkenes take part in addition reactions and form polymers.

Structural isomers have the same molecular formula but different structural formulae.

Give an example of structural isomerism.

molecular formula ........................................

two structural formulae ........................................ and ........................................

Ethene reacts with each of the following. Give the name and structural formula of each product.

Alkenes polymerise by addition.

A compound X contains 82.76% of carbon by mass and 17.24% of hydrogen by mass.

Alkenes are unsaturated hydrocarbons.

What is meant by the term unsaturated hydrocarbon?

unsaturated ..................................................

hydrocarbon ..................................................

Describe a test that would distinguish between saturated and unsaturated hydrocarbons.

reagent ..................................................

observation (saturated hydrocarbon) ..................................................

observation (unsaturated hydrocarbon) ..................................................

Addition polymers can be made from alkenes. The diagram shows part of an addition polymer.

Alkenes can form polymers.

What type of polymerisation occurs when alkenes form polymers?

Part of the structure of a polymer is shown.

Draw the structure of the alkene from which this polymer can be made. Show all of the atoms and all of the bonds.

Part of the structure of a polyamide is shown.

This polyamide is formed from identical monomers. Complete the diagram to show the structure of one monomer. Show all of the atoms and all of the bonds.

Petroleum (crude oil) is a mixture of hydrocarbons.

Petroleum (crude oil) is separated into fractions such as liquefied petroleum gas, petrol (gasoline) and naphtha.

The structure of chloroethene is shown.

Chloroethene is the monomer used to make poly(chloroethene).

Poly(chloroethene) is non-biodegradable.

There are two types of polymerisation, addition and condensation.

Explain the difference between these two types of polymerisation.

Some plastics, formed by polymerisation, are non-biodegradable.

Describe two pollution problems that are caused by non-biodegradable plastics.

The polymer known as PVA is used in paints and adhesives. Its structural formula is shown below.

Deduce the structural formula of its monomer.

A condensation polymer can be made from the following monomers.

Draw the structural formula of this polymer.

A South Korean chemist has discovered a cure for smelly socks. Small particles of silver are attached to a polymer, poly(propene), and this is woven into the socks.

[1]

[2]

[2]

To show that the polymer contains silver the following test was carried out. 

The polymer fibres were chopped into small pieces and warmed with nitric acid. The silver atoms were oxidised to silver(I) ions. The mixture was filtered. Aqueous sodium chloride was added to the filtrate and a white precipitate formed.

[1]

[1]

[1]

Propanoic acid is a weak acid.

[2]

[1]

Monomers polymerise to form polymers or macromolecules.

An important monomer is chloroethene which has the structural formula shown below.

It is made by the following method.

This is heated to make chloroethene.

Synthetic polymers are widely used in the modern world.

Their use has brought considerable advantages to modern life as well as some disadvantages.

One type of polymer is formed by addition polymerisation.

Nylon is made by condensation polymerisation. It has the structural formula shown below.

Esters, fats and polyesters all contain the ester linkage.

The structural formula of an ester is given below.

Name two chemicals that could be used to make this ester and draw their structural formulae. Show all bonds.

Cooking products, fats and vegetable oils, are mixtures of saturated and unsaturated esters.

The degree of unsaturation can be estimated by the following experiment. 4 drops of the oil are dissolved in 5 cm³ of ethanol. Dilute bromine water is added a drop at a time until the brown colour no longer disappears. Enough bromine has been added to the sample to react with all the double bonds.

A better way of measuring the degree of unsaturation is to find the iodine number of the unsaturated compound. This is the mass of iodine that reacts with all the double bonds in 100 g of the fat.

Use the following information to calculate the number of double bonds in one molecule of the fat.

Mass of one mole of the fat is 884 g.

One mole of I₂ reacts with one mole C=C.

The iodine number of the fat is 86.2 g.

Complete the following calculation.

100 g of fat reacts with 86.2 g of iodine.

884 g of fat reacts with .............................. g of iodine.

One mole of fat reacts with .............................. moles of iodine molecules.

Number of double bonds in one molecule of fat is ..............................

Polymers are extensively used in food packaging. Poly(dichloroethene) is used because gases can only diffuse through it very slowly. Polyesters have a high thermal stability and food can be cooked in a polyester bag.

The structure of poly(dichloroethene) is given below.

[1]

[2]

[2]

[1]

[2]

[1]

Alkanes and alkenes are both series of hydrocarbons.

Alkenes and simpler alkanes are made from long-chain alkanes by cracking.

Complete the following equation for the cracking of the alkane C₂₀H₄₂.

C₂₀H₄₂ → 2C₄H₈ + 2C₂H₄ + ...............

Alkenes such as butene and ethene are more reactive than alkanes.

Alkenes are used in the petrochemical industry to make a range of products, which includes polymers and alcohols.

+ Br2 →

20c m³ of a hydrocarbon was burnt in 175 cm³ of oxygen. After cooling, the volume of the remaining gases was 125 cm³. The addition of aqueous sodium hydroxide removed carbon dioxide leaving 25 cm³ of unreacted oxygen.

Esters occur naturally in plants and animals. They are manufactured from petroleum. Ethyl ethanoate and butyl ethanoate are industrially important as solvents.

A polymer has the structure shown below.

Petroleum is a source of many important chemicals.

Name two industrial processes which must take place to produce alkenes from petroleum.

Ethene, CH₂=CH₂, and propene, CH₂=CHCH₃, can both be converted into polymers.

Ethene will react with steam to form ethanol.

Propene will react with steam to form two isomers, both of which are alcohols.

Suggest the structures of these alcohols.

Esters are organic chemicals noted for their characteristic smells. Ethanoic acid and methanol will react to form an ester.

Alkanes and alkenes are examples of hydrocarbons.

A compound X contains carbon, hydrogen and oxygen only.

X contains 54.54% of carbon by mass, 9.09% of hydrogen by mass and 36.37% of oxygen by mass.

An ester has the molecular formula C₃H₆O₂.

Name and give the structural formulae of two esters with the molecular formula C₃H₆O₂.

Name the ester produced from the reaction of propanoic acid and methanol.

A polyester is represented by the structure shown.