Suggested Teaching Scheme - STMGSSintranet.stmgss.edu.hk/~ted/ccy/new_edition/Book3Aanswer.pdf · Suggested teaching scheme for the curriculum ... source_phy/flash/ formation_e.html

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Suggested Teaching Scheme


The following suggested teaching schemes are for teachers’ reference only. Teachers may revise them based on the time-tabling arrangement of their own schools.

Scheme 1: Chemistry to be studied in Secondary 3, 4, 5 and 6In many schools, the Chemistry curriculum is studied in Secondary 3, 4, 5 and 6. Although the distribution of periods varies from school to school, the total number of periods for the curriculum is generally around 4�6. A possible distribution of periods is as follows:

A possible distribution of periods for S3, S4, S5 and S6

S3 S4 S5 S6

Number of teaching weeks per year 28 28 28 �6

Number of periods per week 2 5 5 5

Total number of periods per year 56 �40 �40 80

Total number of periods for the curriculum 4�6

Suggested teaching scheme for the curriculum

Level ContentSuggested number

of period(s)

S3(56 periods)

Topic � Planet Earth �2

Topic 2 Microscopic World I 44

S4(�40 periods)

Revision on laboratory safety �

Topic 3 Metals 39

Topic 4 Acids and Bases 45

Topic 5 Redox Reactions, Chemical Cells and Electrolysis 4�

Topic 6 Microscopic World II �4

S5(�40 periods)


Topic 7 Fossil Fuels and Carbon Compounds 32

Topic 8 Chemistry of Carbon Compounds 45

Topic 9 Chemical Reactions and Energy �3

Topic �0 Rate of Reaction �6

Topic �� Chemical Equilibrium �8

Topic �2 Patterns in the Chemical World �5

S6(80 periods)


Topic �3 Industrial Chemistry 39

Topic �4 Materials Chemistry 39

Topic �5 Analytical Chemistry 40

Schools taking investigative study need to allocate an extra of 30 periods for the curriculum.

Only 2 out of 3 Only 2 out of 3

2

Topic 7 Fossil Fuels and Carbon Compounds

Scheme 2: Chemistry to be studied in Secondary 4, 5 and 6In some schools, the Chemistry curriculum is studied in Secondary 4, 5 and 6. The total number of periods for the curriculum is generally around 360. A possible distribution of periods is as follows:

A possible distribution of periods for S4, S5 and S6

S4 S5 S6

Number of teaching weeks per year 28 28 �6

Number of periods per week 5 5 5

Total number of periods per year �40 �40 80

Total number of periods for the curriculum 360

Suggested teaching scheme for the curriculum

Level ContentSuggested number

of period(s)

S4(�40 periods)

Topic � Planet Earth 8

Topic 2 Microscopic World I 3�

Topic 3 Metals 32

Topic 4 Acids and Bases 36

Topic 5 Redox Reactions, Chemical Cells and Electrolysis 33

S5(�40 periods)


Topic 6 Microscopic World II �3

Topic 7 Fossil Fuels and Carbon Compounds 29

Topic 8 Chemistry of Carbon Compounds 4�

Topic 9 Chemical Reactions and Energy �2

Topic �0 Rate of Reaction �5

Topic �� Chemical Equilibrium �6

Topic �2 Patterns in the Chemical World �3

S6(80 periods)


Topic �3 Industrial Chemistry 39

Topic �4 Materials Chemistry 39

Topic �5 Analytical Chemistry 40

Schools taking investigative study need to allocate an extra of 30 periods for the curriculum.

Only 2 out of 3 Only 2 out of 3

3


Suggested number of periods for Topic 7

Chemistry forTotal number

of periodsSuggested number of periods for each unit

S3–S6(Scheme �)

32

Unit 25 Fossil fuelsUnit 26 Homologous series, structural formulae and

naming of carbon compoundsUnit 27 Alkanes and alkenesUnit 28 Addition polymers

�0

88

�0

S4–S6(Scheme 2)

29

Unit 25 Fossil fuelsUnit 26 Homologous series, structural formulae and

naming of carbon compoundsUnit 27 Alkanes and alkenesUnit 28 Addition polymers

9

789

4


Carbon compounds play an important role in industry and in daily life. Coal and petroleum are two major sources of carbon compounds. The main focus of Unit 25 is on the use of petroleum fractions as fuels and as raw materials in the petrochemical industry. Students should appreciate that the use of fossil fuels has brought us benefits and convenience, alongside with environmental problems such as air pollution, acid rain and the global warming.

A look at the molecules of compounds in petroleum leads to a study of alkanes in Unit 26. This unit also covers some basic concepts of carbon chemistry such as homologous series, functional group, general formula and structural formula. Students also learn to give systematic names of alkanes, alkenes, alkanols and alkanoic acids with carbon chains containing up to eight carbon atoms.

Unit 27 covers the important reactions of alkanes and alkenes. By illustrating the formation of chloromethane with electron diagrams, students should realize that chemical reactions often take place in more than one step and involve reactive species.

Plastics are remarkably useful materials mainly derived from fossil fuels. Students should know that ‘plastics’ is a collective term which embraces a large number of polymers. Unit 28 covers several common addition polymers. Students should understand how the polymers are formed and relate their uses to their structures. On the other hand, students should be aware of the environmental issues associated with extensive use of plastics. It is therefore necessary to explore appropriate methods for treating plastic waste.

Organization of the topic

Teaching Plan

Fossil Fuels and Carbon Compounds

Unit 26Homologous series, structural formulae

and naming of carbon compounds

Unit 25Fossil Fuels

Unit 27Alkanes and alkenes

Unit 28Addition polymers

5

Teaching Plan

Section Key point(s)Suggested task(s) for

studentsRemark

Total number of periods = 2

25.� Fossil fuels — a major energy source

• Formation of coal• Formation of petroleum

and natural gas

• Discussion

• Do you know — China’s dependence on

coal for energy supply

• Refer to the following

website for the information on different sources of energy in Hong Kong:

http://resources.edb.gov.hk/~senergy/power/print/source_is_print_e.html

(accessed August 20�4)

• Refer to an animation

on the formation of coal, oil and natural gas:

http://resources.edb.gov.hk/~senergy/power/source_phy/flash/formation_e.html


25.2 Importance of petroleum

• Main uses of refined petroleum

• Economic importance of petroleum


25.3 Hydrocarbons • Definition• Types of hydrocarbons

25.4 What does petroleum contain?

• Hydrocarbons in petroleum

– alkanes – cycloalkanes – aromatic hydrocarbons

Unit 25 Fossil fuels

Continued on next page

6



studentsRemark

25.5 Fractional distillation of petroleum

• How fractional distillation of petroleum is carried out in an oil refinery

• Fractional distillation of crude oil in the laboratory

• Properties of fractions of petroleum with different boiling point ranges

• Activity 25.� — Fractional distillation

of crude oil and studying the properties of its fractions

• Fractional distillation of petroleum

• Refer to an animation on the fractional distillation of petroleum in industry:

– http://ibchem.com/IB/ibnotes/full/ope_htm/oil_refining.htm

(accessed August 20�4) – http://www.

howstuffworks.com/oil-refining4.htm


• Fractional distillation of

crude oil

• Refer to an animation illustrating the flammability of different petroleum fractions:

http://www.absorblearning.com/media/item.action?quick=��n


• Refer to an animation demonstrating the viscosity of different petroleum fractions:

http://www.absorblearning.com/media/item.action?quick=��m

(accessed August 20�4)• Do you know — Getting the volatility right


25.6 Major uses of fractions of petroleum

• Major uses of fractions of petroleum

• Practice 25.�


7

Teaching Plan


studentsRemark

Total number of period = 1

25.7 Combustion of hydrocarbons

• Exothermic and endothermic reactions

25.8 Carbon dioxide and the greenhouse effect

• What the greenhouse effect is

• How carbon dioxide causes the greenhouse effect

• Practice 25.2 • Do you know — Methane as a

greenhouse gas• Do you know — International

cooperation to fight against global warming


25.9 Major air pollutants from cars, factories, incinerators and power plants

• Carbon monoxide• Unburnt hydrocarbons• Suspended particulates• Oxides of nitrogen• Sulphur dioxide• Effects of the air

pollutants to the environment and human health

• Major air pollutants

and their effects on our health

• Refer to the video clip ‘Environment and sustainable development’（環境與可持續發展）:

http://resources.hkedcity.net/resource_detail.php?rid=345340988

(accessed August 20�4)• Do you know — Effects of acid rain• Do you know — How do oxides of

nitrogen and unburnt hydrocarbons cause photochemical smog?

25.�0 Measures for reducing emission of air pollutants

• Air pollution in Hong Kong

• Using catalytic converters in exhaust systems of motor vehicles

• Practice 25.3

25.�� Impact of using fossil fuels on our quality of life and the environment

• How modern people use fossil fuels

• Impact of using fossil fuels on the environment

• Find & Share — Impacts of using fossil fuels on our quality of life and the environment

8



studentsRemark


26.� A look at molecules of compounds in petroleum

• Boiling points of hydrocarbons in petroleum

• Discussion

26.2 Chemistry of carbon compounds

• Unique features of carbon


26.3 Representing molecules of carbon compounds

• Structural formulae• Condensed structural

formulae• Skeletal formulae

• Practice 26.�

26.4 Molecular models • Ball-and-stick models• Space-filling models

• Molecular model


26.5 Functional groups • What a functional group is

26.6 Homologous series • What a homologous series is

• Characteristics of members in a homologous series

• Some homologous series and the functional groups they contain

• Activity 26.� — Building molecular models of alkanols and alkanoic acids


26.7 The alkanes • General formula of members of the alkane series

• Six simple straight-chain alkanes

• Activity 26.2 — Building molecular models of alkanes

Unit 26 Homologous series, structural formulae and naming of carbon compounds


9

Teaching Plan


studentsRemark

26.8 Naming straight-chain and branched-chain alkanes

• Naming – straight-chain alkanes – branched-chain

alkanes – cycloalkanes

• Practice 26.2 • Refer to the following website for tutorials and exercises on the nomenclature of organic compounds:

http://cd�.edb.hkedcity.net/cd/science/chemistry/resource/naming/t4_main.htm



26.9 Naming alkenes • Naming alkenes with carbon chains containing up to 6 carbon atoms

• Activity 26.3 — Building molecular models of alkenes

• Practice 26.3

26.�0 Naming alkanols • Naming alkanols with carbon chains containing up to 6 carbon atoms


26.�� Naming alkanoic acids

• Naming alkanoic acids with carbon chains containing up to 6 carbon atoms

• Practice 26.4

26.�2 Physical properties of alkanes

• Rise of melting and boiling points of alkanes with the increase of the number of carbon atoms in the alkane molecules

• Solubility and density of alkanes

�0



studentsRemark


27.� Risks and benefits of fossil fuels to the society and environment

• Benefits of using fossil fuels

• Risks of using fossil fuels

• Spillage of petroleum

• Find & Share — Risks and benefits of using fossil fuels to the society and environment

• Do you know — BP oil spill


27.2 Important reactions of alkanes

• Combustion• Reaction with halogens — substitution reactions• Steps involved in the

substitution of methane with chlorine

• Activity 27.� — Investigating the

properties of an alkane• Practice 27.�

• Reaction of an alkane (hexane) with bromine

• Refer to the animation ‘Substitution reaction’:

http://www.youtube.com/watch?v

=MvWQOYLm�f4 (accessed August 20�4)


27.3 Demand for various fractions of petroleum

• Percentages of various fractions obtained from the fractional distillation of petroleum from different parts of the world

• The supply and demand for various fractions

27.4 Cracking • Catalytic cracking• Cracking of tetradecane

as an example• Importance of cracking – Producing extra petrol – As a source of

alkenes• Cracking of medicinal

paraffin in the laboratory

• Activity 27.2 — Cracking of medicinal paraffin and testing the gaseous product

• Practice 27.2

• Cracking of medicinal paraffin and testing the gaseous product

• Refer to the video clip ‘Cracking a hydrocarbon’:

http://www.youtube.com/watch?v=ZYyKUePdC2Y


Unit 27 Alkanes and alkenes


��

Teaching Plan


studentsRemark


27.5 The alkenes • Some straigth-chain alkenes

27.6 Physical properties of alkenes

• Rise of melting and boiling points of alkenes with the increase of the length of carbon chain in the alkene molecules

• Solubility of alkenes in water

27.7 Important reactions of alkenes

• What an addition reaction is

• Reaction with bromine solution

• Reaction with cold acidified dilute potassium permanganate solution

• Test for unsaturation

• Activity 27.3 — Investigating the

properties of an alkene• Activity 27.4 — Distinguishing between

an alkane and an alkene

• Practice 27.3

• Refer to the video ‘Testing for unsaturated hydrocarbons with bromine’:

http://www.youtube.com/watch?feature=player_embedded&v

=PE�CDR�S5pk (accessed August 20�4)

27.8 Wind power — an alternative source of energy

• Wind energy being a renewable energy source

• Limitations of using wind energy

• Chemistry Magazine — The fossil fuel dilemma

• Wind power as an

alternative source of energy

• Wind power station in Hong Kong

• Do you know — Lamma Winds

�2



studentsRemark


28.� Plastic items in modern homes

• Various uses of plastics in modern homes

• Do you know — Birth of the plastics

industry

28.2 Why are plastics so useful?

• General properties of plastics

• Discussion


28.3 What is a polymer? • What a polymer is• Polymerization• Natural and man-made

polymers

28.4 Polymerization of ethene

• Polymerization of ethene

• What addition polymerization is

• What addition polymers are

• What a repeating unit is

• Polythene being an addition polymer

• Low density polythene and high density polythene

• Practice 28.� • Refer to a cartoon showing the processes involved in the production of plastics from petroleum:

http://www.totalpetrochemicalsusa.com/flash/WellheadToPlastics.swf


• Refer to animations showing the polymerization of ethene:

– http://www.absorblearning.com/media/item.action?quick=��s


– http://www.knockhardy.org.uk/polymer.htm


Unit 28 Addition polymers


�3

Teaching Plan


studentsRemark

– http://www.dynamicscience.com.au/tester/solutions/chemistry/polyetheneld.htm


• Do you know — The discovery of

polythene


28.5 Some common addition polymers

• Polypropene (PP)• Polyvinyl chloride (PVC)• Polystyrene (PS)• Perspex

• Discussion • Activity 28.� — Investigating the

properties of some polymers

• Activity 28.2 — Preparing polystyrene• Practice 28.2


28.6 Uses of some common addition polymers

• Uses and properties of some common addition polymers

– low density polythene – high density polythene – polypropene – polyvinyl chloride – polystyrene – Perspex

• Discussion • Practice 28.3

• Refer to an animation showing the injection moulding:

http://www.bpf.co.uk/Data/Image/Injection MouldingAnimation.swf


• Refer to an animation showing the extrusion blow moulding:

http://www.bpf.co.uk/Data/Image/Extrusion%20Blow%20Moulding.swf


�4



page 3N2

Common sources of energy in Hong Kong

In Hong Kong, the most common energy sources are electricity, town gas, liquefied petroleum gas (LPG), diesel and petrol. Town gas and LPG are commonly used for cooking and heating water at home. Petrol is the most common fuel for light vehicles. Ships and heavy vehicles burn diesel as fuel.

Town gas, LPG (contains mainly propane and butane liquefied under pressure), petrol and diesel all come from petroleum. Electricity is generated by nuclear power or by burning fossil fuels like coal and natural gas in power stations.

Town gas

Town gas is not directly obtained by the fractional distillation of petroleum, but by the refining of one of the fractions called naphtha. Town gas consists mainly of hydrogen (49%), methane (28.5%), carbon dioxide (�9.5%), and a small amount of carbon monoxide (3%). Smell is added to the town gas to ensure easy detection in case of gas leak.

Since 2006, natural gas has been introduced as feedstock in addition to naphtha to ensure a more stable supply of town gas and reduce emissions.

Natural gas

In Hong Kong, natural gas is not available for domestic use, but is used in power station to produce electricity. Natural gas is imported to Hong Kong in a gaseous state from the Yacheng Gas Field near Hainan Island through a gas pipe under the sea.

Reference:

http://resources.edb.gov.hk/~senergy/power/print/source_is_print_e.html


Teaching Notes

�5

Teaching Notes

page 4N4

Mining of petroleum

Petroleum is brought to the surface by drilling a hole in the Earth's crust and sinking pipes deep down through the non-porous cap rock. Natural gas first comes out under high pressure. Then petroleum is pumped out, collected in tanks and transported for further processing.

page 18N8

Comparison of concentration levels between clean and polluted air

Component Clean air Polluted air

Carbon dioxide 3�0–33� ppm 350–700 ppm

Carbon monoxide < � ppm 5–200 ppm

Hydrocarbons � ppm �–20 ppm

Suspended particulates �0–20 µg m–3 70–700 µg m–3

Oxides of nitrogen 0.00�–0.0� ppm 0.0�–0.5 ppm

Sulphur dioxide 0.00�–0.0� ppm 0.02–2 ppm

�6


page 21N12

Using scrubbers in power stations to reduce sulphur dioxide emission

Attaching scrubbers to smokestacks of power stations can remove up to 95% of sulphur dioxide from power station gas. In dry scrubbing, powdered limestone is blown into the combustion chamber where it decomposes.

CaCO3(s) CaO(s) + CO2(g)

The calcium oxide is a base which neutralizes sulphur dioxide to form calcium sulphite.

CaO(s) + SO2(g) CaSO3(s)

In wet scrubbing, calcium oxide reacts with water to produce calcium hydroxide solution. The calcium hydroxide solution neutralizes the sulphur dioxide gas.

CaO(s) + H2O(l) Ca(OH)2(aq)

Ca(OH)2(aq) + SO2(g) CaSO3(s) + H2O(l)

These products are washed away as a slurry — a mixture of solids and water.

The operation of scrubber involves neutralization reactions. These have been discussed in Topic 4 Acids and Bases.

�7

Teaching Notes

page 21N13

Using electrostatic precipitators in power stations to reduce particulate emission

This technique removes up to 99% of the particulates. Dirty gases pass through a strong electric field, where the particulates become charged. The charged particulates are then collected on plates of opposite charge.


page 38N1

Distinguishing between ‘structural formula’ and ‘molecular formula’

Students should be able to distinguish between the ‘structural formula’ and the ‘molecular formula’ of a compound.

e.g.

CH2

CH3

CH3

CH3

C CH3CH2

CH3

CH2CH3 CH CH3 and

They are different compounds. Their structural formulae are different but they have the same molecular formula (C6H�4).

�8


page 38N2

Drawing structures of compounds with the same molecular formula

When drawing structures of different compounds with the same molecular formula, do NOT represent the same compound in different ways.

e.g.

H

H

C

H

H

C

H H

H

CH C

H

CH3

C

H

H

H

H

C

H

H

C

H H

H

CH C

H

H

C

H

H

C

H

H and

are two different ways of representing hexane.

e.g.

CH3CH3 H

H

C

H

H

C

H H

H

CH C

H

C

H

H

H

H

C

H

H

CH C

H

H

C

H

H

C

H

H and

are two different ways of representing 2-methylpentane.


page 73N1

Generating electricity by burning fossil fuels

The diagram below illustrates how electricity is generated from fossil fuels. The heat produced by burning fossil fuels is used to convert water into steam. The steam turns a turbine which drives the generator to produce electricity.

�9

Teaching Notes

page 90N12

Test for unsaturation using aqueous bromine

The test for an alkene often involves shaking the substance with aqueous bromine rather than with pure bromine. Decolourization of the aqueous bromine occurs if an alkene is present. In the case of ethene, a mixture of 2-bromoethanol, �,2-dibromoethane and hydrogen bromide is obtained.

+ Br Brin water

2-bromoethanol 1,2-dibromoethane

H

Br

CH

H

OH

C H

H

Br Br

CH

H

C H+ HBr+C CH

H

H

H

page 90N13

• Examination questions often ask about chemical test to distinguish between an alkane (a saturated hydrocarbon) and an alkene (an unsaturated hydrocarbon). Do NOT just state a chemical test, mention the expected observations for the alkane and alkene as well.

• Alkenes give negative results towards acidified potassium dichromate solution. Therefore the reagent CANNOT be used to distinguish an alkene from an alkane.

page 92N14

Renewable and non-renewable energy sources

Non-renewable energy sources are those that are used up at a faster rate than the rate at which they can be produced on Earth. Fossil fuels and nuclear energy are non-renewable energy sources. There is a limited supply of non-renewable energy sources on Earth.

Renewable energy sources are those that can be produced at a faster rate than the rate at which they are used. Solar energy, hydroelectric power and wind energy are renewable energy sources. There is an unlimited supply of renewable energy sources on Earth.

Solar energy

Solar energy is the radiant heat and light energy given out by the Sun. Solar energy can be used to generate electricity and supply heat or hot water for domestic use.

Solar power stations use lots of mirrors to reflect the sun’s rays onto a boiler. The water in the boiler heats up to produce steam. The steam then turns the turbines. The turbines then drive the generators to produce electricity.

Solar energy can also be collected by solar panels fixed on rooftops or nearby buildings and used to heat water for homes.

20


Using solar energy in Hong Kong

To use solar energy, solar photovoltaic technology can also be used. Photovoltaic cells made from semi-conducting materials such as silicon can produce electricity when they are exposed to sunlight. This technology is currently used in Hong Kong to provide power to weather monitoring equipment, as well as lighting and heating systems in many government facilities.

Building Integrated Photovoltaic (BIPV) cells, where photovoltaic cells are included as part of the building structures e.g. in windows and skylights, are also used in Hong Kong under programmes like ‘Building Integrated Photovoltaic School Design for Hong Kong’.

Reference: http://resources.edb.gov.hk/~senergy/power/print/source_is_print_e.html


Hydroelectric power

We can use the kinetic energy of moving water to generate electricity. This is called hydroelectric power. Hydroelectric power is currently the largest source of renewable energy.

Countries with heavy rainfall and mountainous ground are ideal for hydroelectric power. Some hydroelectric plants use naturally falling water. Part of the water is channelled down a pipe and turns a turbine at the bottom. As the turbine spins, it drives a generator and generates electricity.

In other places where there are no natural waterfalls, people hold the water back with a dam. Some of the water is then allowed to rush through a channel, and turns a turbine that drives a generator.

Advantages and limitations of using renewable energy sources

Energy source Advantages Limitations

Solar energy • low air pollution• low water pollution• renewable

• solar panels are expensive to build• difficult to store

Hydroelectric power

• low air pollution• renewable• reservoirs used for recreation purposes

• building huge dams is expensive• may mean flooding a populated valley• may affect wildlife habitats and farming areas• very limited choice of suitable sites

2�

Teaching Notes

World energy demand (1980–2035)

According to the International Energy Agency, global energy demand would grow by 40% between 2009 and 2035, with coal use rising most in absolute terms.

Reference:

World primary energy demand

International Energy Agency (20��) ‘World Energy Outlook 20��’ (Paris: International Energy Agency), retrieved from http://www.iea.org/publications/freepublications/publication/WEO20��_WEB.pdf,p76



page 113N4

Examination questions often ask students to draw the repeating unit of the polymer formed based on the structure of an unfamiliar monomer.

e.g.

H H n

C C

C

H O

H

C

C H

H O

n C

HH

Examination questions may also ask students to draw the structure of the monomer based on the structure of the polymer.

C

H

H

CH2

OCH3

part of structure of Superglue

C

CNe.g.

C O

CH2

OCH3

C

CN

C O

CH2

OCH3

C

CN

C O

OCH3

monomer of Superglue

C

CN

C O

22


CH3e.g.

H

CH3

H n

C C

structure of a polymer

CH3

H

CH3

H

C C

structure of the monomer

page 117N6

Common additives for plastics

Most plastics are blended with additives as they are processed into finished products. The additives are included to make plastics easier to process and to modify their working properties and product performance.

Below are types of common additive used:

• antioxidants — to prevent reaction with oxygen;

• pigments — to give colour;

• stabilizers — to inhibit undesirable degradation in use and prevent colours from fading;

• plasticizers — to make the plastics softer and easier to mould;

• blowing agents — to produce foamed materials;

• fillers — to make the products stronger and opaque.

page 118N8

Uses and structure of polyvinyl chloride

Examination questions often ask about PVC.

• PVC is a thermoplastic produced by addition polymerization.

• Examples of flexible products made of PVC — floor tiles, shower curtains, raincoats, waterproof coating for folders and bags, insulating tapes and coverings around electrical wires, seat coverings for taxis.

• Examples of rigid products made of PVC — drain pipes and bottles.

23

Teaching Notes

Attractions between PVC polymer chains

There are permanent dipole-permanent dipole attractions between the PVC polymer chains. The chains cannot slide past each other easily. Hence PVC is rigid.

C

H

δ+H

C

H

H

C

Cl

δ+H

C

H

H

C

H

δ–Clδ–Cl

C

H

H

C

Cl

δ+H

C C

Cl

H

H

C

δ–Cl δ–Cl

H

C

H

H

C

δ+H

Cl

C

H

H

C

H

permanent dipole-permanent dipole attractions

Structure of PVC with plasticizer

Plasticizers are one type of additive. When added to a polymer, the molecules of the plasticizer get in-between the polymer chains and allow the chains to slide past each other more easily. Products made of PVC with plasticizers are very flexible.

24


page 1

� CH H

H HC

2 Ethene contains carbon-carbon double bond only.

3 As a fuel for transportation / generating electricity / heating


Practice

P25.1 page 13

a) Fractional distillation

b) Refinery gas

c) Diesel oil

d) Kerosene

e) Hydrocarbons in different fractions contain different number of carbon atoms.

P25.2 page 17

a) The Earth’s absorbs Sun’s radiation and also radiates its own infrared radiation.

Greenhouse gases trap some of the infrared radiation which is radiated from the Earth, thus keeping the atmosphere warm for life to sustain on Earth.

b) Any one of the following:

• Burning fossil fuels

• Production of cement

• Making iron / steel

• Deforestation

• Fermentation

• Oil refining

• Respiration

Suggested Answers

25

Suggested Answers

c) Any one of the following:

• The remains / manure of cattles decay to give methane.

• Cattles discharge methane in belches from partly digested food in their guts.

• Action of anaerobic bacteria in environments lacking of oxygen such as wetlands and paddy rice fields.

d) Any two of the following:

• Burn a fuel from a plant source (e.g. bioethanol). Burning the fuel returns carbon dioxide which has been removed from the atmosphere during the photosynthesis.

• Use alternative energy source (e.g. solar energy, wind energy, nuclear, hydroelectric power, geothermal energy)

• Improve the efficiency of the process. / Use a catalyst so that the process requires less activation energy.

P25.3 page 24

� a) Reduce the amount of

• carbon dioxide;

• unburnt hydrocarbons;

• suspended particulates;

• oxides of nitrogen

in the exhaust gas.


• Nitrogen

• Water

• Carbon dioxide

c) Platinum / rhodium

Larger surface area available for reaction.

2 a) The fossil fuels used contain sulphur.

When the fuel burns, the sulphur is oxidized to sulphur dioxide.

b) Use low-sulphur coal.

Install flue gas desulphurization system / scrubbers.

26


Discussion page 3

� Uses of coal:

• electricity generation;

• iron extraction — a blast furnace uses iron ore, coke (made from coal), and limestone;

• cement making — coal is an important energy source in the cement industry.

Uses of petroleum:

• as fuels for transportation;

• as fuels for generating electricity;

• as fuels for heating;

• as raw materials in the petrochemical industry.

Uses of natural gas:

• as a fuel for powering boilers that create heat for homes and office buildings in low temperature climates;

• as a fuel for cooking;

• electricity generation — natural gas has become a very popular fuel for electricity generation because of its clean burning nature;

• as a feedstock for manufacturing of other chemicals, such as propane and butane.

2 This question helps to sensitize students’ awareness of the importance of fossil fuels in their daily lives.

page 24Find & Share

Impacts of using fossil fuels on our quality of life and the environment

What is the quality of life?

According to the World Bank, ‘quality of life’ refers to people's overall well-being. Quality of life is difficult to measure because in addition to material well-being (the level of well-being as measured by the level of income or by the quantity of various goods and services consumed), it includes such intangible components as the quality of the environment, national security, personal safety, and political and economic freedoms.

Uses of petroleum fractions

Uses of petroleum fractions fall into 3 major categories:

• fuels such as petrol and diesel fuel;

• non-fuel products such as solvents and lubricating oils;

• feedstocks for the petrochemical industry such as naphtha.

(Refer to the detailed information under Section 25.6 ‘Major uses of fractions of petroleum’ on pages �2–�3 of the textbook.)

27

Suggested Answers

Many of the benefits we derive from our way of life, and our high standard of living, are due to fossil fuel use. Light, heat, food, communication, travel, community — all are based on our ability to produce and use energy. And most of our energy comes from fossil fuels.

Researchers have studied the relationship between per capita energy use or electricity consumption and a variety of basic quality of life measures. They found that as the per capita electricity or energy use in a country rises so does life expectancy, literacy, education, GDP and access to clean water. At the same time, infant and maternal mortality rates decrease.

Energy and quality of life studies indicate that energy use, up to certain levels, enables improvements in these basic measures of quality of life. However, increasing energy use beyond these levels yields diminishing returns.

Environmental impacts of using fossil fuels

Fossil fuel combustion is the leading contributor to global warming. Most air pollution also comes from the combustion of fossil fuels.

References:

http://www.elca.org/JLE/Articles/343


pages 29–34Unit Exercise

� a) fossil fuels

b) coal

c) natural gas

d) hydrocarbons

e) alkanes

f) cycloalkanes

g)

H

H

H

H

HH

HH

C

C C

C

C

H H H

CC

C

C

CC

H

H

H

H

Hcyclopentanebenzene

28


h)

H

H

H

H

HH

HH

C

C C

C

C

H H H

CC

C

C

CC

H

H

H

H

Hcyclopentanebenzene

i) fractional

j) lower boiling point range

k) lighter in colour

l) less viscous

m) easier to evaporate (or more volatile)

n) more flammable; burns with a clearer flame

o) higher boiling point range

p) darker in colour

q) more viscous

r) more difficult to evaporate (or less volatile)

s) less flammable; burns with a sootier flame

2 a) suspended particulates

b) carbon monoxide

c) unburnt hydrocarbons

d) oxides of nitrogen

e) sulphur dioxide

f) photochemical smog

g) acid rain

3 a) diesel oil

b) lubricating oil and wax

c) bitumen

d) manufacturing town gas

e) as fuel for aircraft / domestic fuel

f) as lubricating oil for machines / making candles

29

Suggested Answers

4 A

5 B

6 D Fuel oil Naphtha

darker in colour lighter in colour

less flammable more flammable

quick thick very runny

less volatile more volatile

7 A

8 D

9 D Pollutant Effect

Carbon monoxide • a very poisonous gas

Oxides of nitrogen• irritate and attack the respiratory system and the lungs• form acid rain• give photochemical smog

Sulphur dioxide• irritates respiratory system• affects functioning of lungs• forms acid rain

Unburnt hydrocarbon • may cause lung cancer

�0 C

�� D (�) The boiling point range of diesel is higher than that of petrol.

�2 D

�3 C (2) This hydrocarbon contains a benzene ring. It is an aromatic hydrocarbon.

�4 B

�5 D

30


�6 A (�) Sulphur dioxide can dissolve in rainwater to form acid rain. Installing scrubbers in power plants can reduce the emission of sulphur dioxide.

(2) Using particulate removal devices in motor vehicles can reduce the emission of particulates.

(3) Installing electrostatic precipitates in power plants can reduce the emission of particulates.

�7 Any one of the following advantages:

• Coal energy is an affordable energy source because of coal’s stable price compared to petroleum.

• Coal is easy to burn.

• Coal produces a lot of energy upon combustion.

• Coal is abundant.

• Coal is a reliable energy source.

• Coal is widely distributed all over the world.

Any two of the following disadvantages:

• Coal containings sulphur which burns to from sulphur dioxide which causes acid rain.

• Ash / smoke / soot / particulates formed.

• Sulphur burns to from sulphur dioxide which irritates respiratory system / affects functioning of lungs.

�8 a) Hydrogen

It releases most energy. It produces water only when burnt.


• Whether it is readily available.

• How long it will last.

• Whether it is renewable.

• Whether it is easy to use.

• Whether it is easy to store.

• Whether it is toxic.

• Whether it is expensive.

• Whether it is volatile.

• Whether it is viscous.

• Whether it is a solid, liquid or gas.

3�

Suggested Answers

�9 a) Petroleum fractions are used as raw materials to produce different chemicals in the petrochemical industry. These chemicals can be made into many useful products, such as plastics and detergents.

b) By fractional distillation

c) i) To avoid spilling if the apparatus is mishandled during assembly.

ii) To condense various fractions obtained in the process.

iii) To measure the boiling points of each fraction coming out.

d) i) Fraction I

ii) Fraction IV

iii) Fraction I

iv) Fraction IV

20 a) i) Carbon monoxide is produced by the incomplete combustion of petrol in the car engine.

ii) Inside car engines, the air gets so hot that nitrogen and oxygen react to form nitrogen monoxide

which can be further oxidized to nitrogen dioxide.

b) Acid rain / photochemical smog

c) Carbon monoxide reacts with nitrogen monoxide as they pass through the catalyst in the catalytic converter. Less harmful carbon dioxide and nitrogen are formed.

catalyst 2CO(g) + 2NO(g) 2CO2(g) + N2(g)

d) The statement is wrong.

Catalytic converters increase the emission of carbon dioxide which contributes to the greenhouse effect.

2� a) i) Fractional distillation

ii) Heat the crude oil to obtain a mixture of liquid and vapour. Pass the mixture into a fractioning tower.

The liquid flows to the bottom of the tower.

The vapours cool down as they rise through the tower. They condense to liquid at different heights.

Vapour containing hydrocarbons with smaller molecular masses condenses in the trays near to the top of the tower.

b) i) Bitumen

ii) Gasoline

iii) Bitumen

iv) Refinery gases and fuel oil

32


22 Answers for the HKDSE question are not provided.

23 a) The number of motor vehicles increases rapidly. Burning large amount of petrol / diesel produces carbon dioxide.

The rapid growth in population leads to deforestation, providing more land for housing. Thus, less carbon dioxide is removed from the atmosphere by photosynthesis.

b) i) The Earth absorbs the Sun’s radiation and also radiates its own infrared radiation.

Greenhouse gases trap some of the infrared radiation which is radiated from the Earth, keeping the atmosphere warm for life to sustain on Earth.

ii) Increase in temperature of the atmosphere can cause melting of polar ice caps and glaciers at high altitude regions / flooding / change in rainfall pattern.

iii) Any two of the following:

• Reduce the use of fossil fuel by using alternative energy sources to generate electricity, e.g. wind energy.

• Use hydrogen as fuel in fuel cells for cars.

• Stop cutting down or burning forests.

• Plant more trees.


Practice

P26.1 page 41

� a) CH3CH2CH2CH2CH2CH3 or CH3(CH2)4CH3

b) CH3CHCH3

OH

or CH3CH(OH)CH3

c) CH3CH=CHCH3

2 a)

b)

c)

33

Suggested Answers

P26.2 page 51

�

methyl group

CH3 CH3

CH2

4CH2

CH3

CH3

3C 2C 1C

H

H

H

H

Ha) H H

1C 2C 3C

H

H

H

5CH3

H

C

H

H

H

H

b)

6C 5C 4C 3C 2C 1C

H

H

H

CH3

H

H

H HH

H

Hc)

d)

H

methyl group

methyl group

ethyl group

methyl group

methyl group

methylpropane

2,3-dimethylpentane

4-ethyl-2,4-dimethylhexane

2-methylbutane

1CH32CH(CH3)

3CH24CH3

methyl group

CH3 CH3

CH2

4CH2

CH3

CH3

3C 2C 1C

H

H

H

H

Ha) H H

1C 2C 3C

H

H

H

5CH3

H

C

H

H

H

H

b)

6C 5C 4C 3C 2C 1C

H

H

H

CH3

H

H

H HH

H

Hc)

d)

H

methyl group

methyl group

ethyl group

methyl group

methyl group

methylpropane

2,3-dimethylpentane

4-ethyl-2,4-dimethylhexane

2-methylbutane

1CH32CH(CH3)

3CH24CH3

2

CH3CCH2CH3 CH3C(CH3)2CH2CH3or

CH3

CH2a)

CH2

CH3

CH

H

H

C

H

H

C

H

H

C

CH3

C

H

H

C

H

H

H

b)

34


P26.3 page 55

�

2-methylbut-2-ene

4-ethyl-3-methylhex-2-ene

4-methylpent-1-ene

3-methylcyclohexene

methyl group

CH3

5(CH3)24CH3CH2

2CH 1CH2

1

2

3

methyl group

methyl group

CH3

3C

4CH3

2C1C

H

H H

Ha)

ethyl group

CH3

CH2

4C5C6C

H

H

H H

3C 2C 1C

H

H

H H

b)

c)

d)

CH3 H H

2

CH2

CH

H

H

C

H

H

C

CH3

C

H

C

H

H

H

b)

CH3 CH3

CH

H

H

C C

H

C

a)

H

H

35

Suggested Answers

P26.4 page 59

�

the –O–H group attached to the second carbon atom

carbon atom of the –COOHgroup is assigned number 1

CH3

3C 2C 1C

H O

H

H

H

H

Ha) H H

3C 2C 1C

H

H

O

H

O H

Hc)

b)

methyl group

propan-2-ol

methylpropanoic acid

pentan-2-ol

5CH34CH2

3CH22CH(OH)1CH3

2 CH3

CH

H

H

C

H

H H H

C C

H

O H

a)

CH3

CH

H H

H

C

O

C C O H

H H

b)

Discussion page 35

� Arrange the data in increasing number of carbon atoms in the molecular formula of hydrocarbon.

2 Hydrocarbon Molecular formula Boiling point (°C)

Methane CH4 –�62

Ethane C2H6 –89

Propane C3H8 –42

Butane C4H�0 –0.5

Pentane C5H�2 36

Hexane C6H�4 69

Heptane C7H�6 98

Octane C8H�8 �26

36



� a) functional group

b) general

c) –CH2–

d) physical

e) chemical

2 Name of homologous

seriesFunctional group General formula

Example

Name Structural formula

Alkane — CnH2n+2 ethane

O H

C C

CH

H

H

C

H

H

H

CH

H

H

C

H

H

OH

CH

H

H

C

O

O H

H

H

H

HAlkene

O

OC H

C C CnH2n ethene

O H

C C

CH

H

H

C

H

H

H

CH

H

H

C

H

H

OH

CH

H

H

C

O

O H

H

H

H

H

Alkanol O H

C C

CH

H

H

C

H

H

H

CH

H

H

C

H

H

OH

CH

H

H

C

O

O H

H

H

H

H

CnH2n+1OH ethanol

O H

C C

CH

H

H

C

H

H

H

CH

H

H

C

H

H

OH

CH

H

H

C

O

O H

H

H

H

H

Alkanoic acidO

OC H

C C

CnH2n+1COOH ethanoic acid

O H

C C

CH

H

H

C

H

H

H

CH

H

H

C

H

H

OH

CH

H

H

C

O

O H

H

H

H

H

3 Name Molecular formula Condensed structural formula

Methane CH4 CH4

Ethane C2H6 CH3CH3

Propane C3H8 CH3CH2CH3

Butane C4H10 CH3(CH2)2CH3

Pentane C5H12 CH3(CH2)3CH3

Hexane C6H14 CH3(CH2)4CH3

Heptane C7H�6 CH3(CH2)5CH3

Octane C8H18 CH3(CH2)6CH3

37

Suggested Answers


Ethene C2H4 CH2=CH2

Propene C3H6 CH3CH=CH2

But-1-ene C4H8 CH3CH2CH=CH2

But-2-ene C4H8 CH3CH=CHCH3

Pent-�-ene C5H10 CH3CH2CH2CH=CH2

Pent-2-ene C5H10 CH3CH2CH=CHCH3


Methanol CH3OH CH3OH

Ethanol C2H5OH CH3CH2OH

Propan-�-ol C3H7OH CH3CH2CH2OH

Propan-2-ol C3H7OH CH3CH(OH)CH3

Butan-1-ol C4H9OH CH3CH2CH2CH2OH

Butan-2-ol C4H9OH CH3CH2CH(OH)CH3

6 a) B

b) C

c) F

d) A and E

7 C

CH3

C2H5

CH3

CH3 C

H

C

H

C

H

H

parent chain containing 6 carbon atoms, i.e. hexane

methyl group attached to the third carbon atom

56 4 3

1,2

\ the IUPAC name of the compound is 3,3-dimethylhexane.

38


8 C CH3 methyl group attached to the third carbon atom

15

4 2

3

\ the IUPAC name of the compound is 3-methylcyclopentene.

9 D The structural formula of is shown below:

H3C CH3

C C

H methyl group attached to the second carbon atom

parent chain containing 4 carbon atoms, with the double bond between the second and third carbon atoms, i.e. but-2-ene

CH3

3 2

4 1

\ the IUPAC name of the compound is 2-methylbut-2-ene.

�0 B

OH

C2H5

CH

H

C

H

H

HC

H

parent chain containing 4 carbon atoms, with the –OH group attached to the second carbon atom, i.e. butan-2-ol

methyl group attached to the second carbon atom1 2

3,4

\ the IUPAC name of the compound is 2-methylbutan-2-ol.

�� B

�2 D C5H�2 is the MOLECULAR FORMULA of the compound.

�3 B Option A — The members have the same general formula.

Option B — Each successive member in a homologous series differs from the next by a –CH2– unit, i.e. the relative molecular mass differs by �4.

Option C — The volatility of the members decreases with relative molecular mass.

Option D — The boiling point of the members increases with increasing number of carbon atoms per molecule.

�4 B Options B and D — Hexane molecule has a linear shape while 2-methylpentane has a more spherical and compact shape. The molecular shape of hexane allows greater surface contact between molecules. Thus, the van der Waals’ forces in hexane are stronger than those in 2-methylpentane. Thus, the boiling point of hexane is higher.

39

Suggested Answers

�5 B The strength of van der Waals’ forces in alkanes increases with the number of electrons in the molecule.

�6 B

�7 C (�) 2-methylpentane is insoluble in water.

(3) Both 2-methylpentane and hexane have the molecular formula C6H�4.

�8 A (�) Compound Name

Homologous series to which it belongs

State at room temperature and pressure

C2H4 ethene alkene gaseous

C3H8 propane alkane gaseous

C4H�0 butane alkane gaseous

(2) C2H4 is an unsaturated hydrocarbon while C3H8 and C4H�0 are saturated hydrocarbons.

(3) They have different physical properties, such as melting and boiling points.

�9 A (�) Both P and Q are alkanes. Thus, they have the same general formula CnH2n+2.

(3) Both P and Q are insoluble in water.

20 B (�)CH3

CH

H H

C

H

H

OC H

H

parent chain containing 3 carbon atoms, with the –OH group attached to the first carbon atom, i.e. propan-1-ol

methyl group attached to the second carbon atom, it is not necessary to specify the location of the methyl group as there is no other combination for a methyl group attached to a three-carbon parent chain.3 2 1

\ the IUPAC name of the compound is methylpropan-�-ol.

(3) The –CH3 group is NOT a functional group.

40


2�

OHC

H

H

H

H

H

H

H

H H

H H

C

C

C

CC

OH

CH3a)

H C

H

C

H

C

H

H H

H

b)

H C

H H

C

H

C

H H

C

HH H

H

CH3c)

H C

H

C

H

CH3

C

H

C

H H

C

HH H

H

CH3d)

H C

H

C

H

C

H

C

H

H

H

e)

H C

H H

C

H

CH3

CC

H H

C

H

C

HH H

H

OHf)

H C

H H

C

H

C

H

C

HH H

H

OH

CH3

g)

H C

H H

C

H

C

H H

C C

HH H

H

h)

H C

H H

C

H

C

H O

C

H H

i)

22 a) CH3CH2CH2CH3 or CH3(CH2)2CH3

b) CH3CH2CH(CH3)CH2CH3

c) CH3CH2CH=CHCH3

d) CH3CH(OH)CH3

23 a) propane

b) pentane

c) 2-methylbutane

d) 3,4-dimethylhexane

e) but-2-ene

f) 3-methylpent-�-ene

4�

Suggested Answers

24 a) CnH2n+2

b)

C

H

HHH

Name of shape: tetrahedral

c) Chemical properties: similar

Named physical property: boiling point increases. / density increases.

25 a) methylpropan-�-ol

b) 3-ethylpentan-�-ol

c) butan-2-ol

d) propanoic acid

e) 5-methylhexanoic acid

26 a) A family of compounds having the same functional group and the same general formula.

b) The boiling point of a compound depends on the strength of its intermolecular attractions.

An alkane molecule becomes larger and heavier as the number of carbon atoms in the molecule increases. The number of electrons in the molecule also increases.

Hence the van der Waals’ forces between the molecules increase.

Thus more heat is needed to separate the molecules during boiling.

27 a) i) They contain atoms of hydrogen and carbon only.

ii) All the atoms are connected by single bonds.

b) i) Alkane

ii) CnH2n+2


• Each member in a homologous series differs from the next by a –CH2– unit.

• They show a gradual change in physical properties.

• They show similar chemical properties.

c)

H C

H H

C

H

C

H

H H

H

42


28 a)

Hydrocarbon Molecular formula Skeletal formula

Aliphatic hydrocarbon or aromatic

hydrocarbon?

IUPAC name

W C6H6aromatic

hydrocarbonbenzene

X C6H12aliphatic

hydrocarboncyclohexane

Y C6H14aliphatic

hydrocarbonhexane

Z C6H14aliphatic

hydrocarbon2,2-dimethylbutane

b) The boiling point of hydrocarbon Y is higher than that of hydrocarbon Z.

Molecule of hydrocarbon Y is longer and somewhat spreadout while that of hydrocarbon Z is more spherical and compact.

The shape of molecule of hydrocarbon Y allows greater surface contact between molecules.

Thus the van der Waals’ forces in hydrocarbon Y are stronger than that in hydrocarbon Z.

Hence the boiling point of hydrocarbon Y is higher than that of hydrocarbon Z.

c) Decane is more viscous than hydrocarbon Y.

A decane molecule has a larger molecular mass / size (or a greater number of electrons) than a hydrocarbon Y molecule. Therefore decane has stronger intermolecular forces than hydrocarbon Y.

Also decane molecules in the form of long chains can become entangled. Hence the relative motion between the molecules will be hindered.

Therefore decane is more viscous than hydrocarbon Y.

43

Suggested Answers


Practice

P27.1 page 80

� The number of carbon atoms per molecule in LPG is lower than that in petrol.

LPG burns more completely, producing less particulate / carbon monoxide.

2 a) The mixture turns from reddish brown to colourless.

b) Substitution reaction

c) The reaction gives a mixture of products (C2H4Br2, C2H3Br3, etc.)

P27.2 page 85

a) Petroleum

b) i) C�2H26

ii) C�2H26 C6H�4 + 2C3H6

iii) Heat to vaporize alkane X.

Pass the vapour over a catalyst.

iv) To meet the large demand of lighter fractions, fractions with smaller number of carbon atoms per molecule.

P27.3 page 92

� Any two of the following:

• Members of the same homologous series have the same general formula. The general formula for propene and but-�-ene is CnH2n. / Each member in a homologous series differs from the next by a –CH2– unit.

• Members of the same homologous series show similar chemical properties. Both ethene and but-�-ene can undergo addition reaction with bromine dissolved in an organic solvent / cold acidified dilute potassium permanganate solution.

• Members of the same homologous series show a gradual change in physical properties. The boiling point of but-�-ene is higher than that of ethene.

2 a) Cracking

b) As a catalyst

c) i) There is no colour change in the solution.

Because no acidic gas is formed in the process.

44


ii) There is a colour change in the solution / the solution changes from purple to colourless.

Because alkenes are formed in the process.

The purple permanganate ions in the solution in tube C are reduced to manganese(II) ions, which are very pale pink in colour / colourless, by the gas passing through the solution.

3 a) Carbon Hydrogen Oxygen

Mass of element in the compound

0.900 g 0.200 g 0.400 g

Number of moles of atoms that combine

0.900 g�2.0 g mol–� = 0.0750 mol

0.200 g�.0 g mol–� = 0.200 mol

0.400 g�6.0 g mol–� = 0.0250 mol

Simplest ratios of atoms

0.0750 mol0.0250 mol

= 3.000.200 mol0.0250 mol

= 8.000.0250 mol0.0250 mol

= �.00

\ the empricial formula of Z is C3H8O.

Let (C3H8O)n be the molecular formula of Z.

Relative molecular mass of Z = n(3 x �2.0 + 8 x �.0 + �6.0) = 60n

i.e. 60n = 60.0 n = �

\ the molecular formula of Z is C3H8O.

b)

OH

propan-1-ol

H C

Hi) H

C

H

C

H

H H

H

OH

propan-2-ol

H C

Hii) H

C C

H

H H

45

Suggested Answers

page 72Find & Share

Risks and benefits of using fossil fuels to the society and environment

Fossil fuel consumption

The following graph shows the world total energy demand by fuel (�980–2035). According to ‘International Energy Outlook 20��’, world energy consumption is projected to increase by 40% from 2009 to 2035.

Useful chemicals produced from the petrochemical industry

Uses of petroleum fractions fall into 3 major categories:

• fuels such as petrol and diesel fuel;

• non-fuel products such as solvents and lubricating oils;

• feedstocks for the petrochemical industry such as naphtha.

The following diagram shows the daily world refinery production demand in 20��.

Refinery gases

Refinery gases are used as feedstocks for petrochemical production processes. They are also used as fuels for domestic heating and cooking.

◀ Residual fuel includes refinery fuel oil. Other includes bitumen, lubricants, waxes,

still gas, coke, sulphur, direct use of crude oil, etc.

46


Petrol

Petrol is a light fraction of petroleum which is quite volatile and burns rapidly. It is used in internal combustion engines such as motor vehicles, excluding aircraft. The important qualities for petrol include octane number (antiknock) and volatility.

Knocking is something we want to try to prevent in petrol engines. It occurs in four stroke engines when some hydrocarbons ignite too early. It causes a knocking sound and reduces the engines performance.

We measure the problem using the octane number. The higher the number, the better the fuel. A fuel with a low octane number is likely to cause knocking. One with an octane number over �00 should be fine.

The addition of tetraethyllead(IV) to retard the combustion was initiated in the �930s but was discontinued in the �980s because of the toxicity of the lead compounds discharged in the combustion products.

Petrol used in automobiles boils mainly between 30 °C–200 °C, the blend being adjusted to altitude and season. For example, in hotter climates, petrol components of higher relative molecular masses with lower volatility are used.

Naphtha

Naphtha is a basic feedstock for the petrochemical industry (e.g. ethene manufacture, town gas production).

Kerosene

Kerosene comprises petroleum distillate intermediate in volatility between petrol and diesel oil.

Kerosene finds considerable use as a jet fuel and around the world in cooking and space heating. When used as a jet fuel, some of the critical qualities are:

• freeze point;

• flash point (the lowest temperature at which a volatile fuel produces enough vapour to form an explosive mixture when it comes in contact with a flame); and

• smoke point (the maximum flame height in millimeters at which a kerosene will burn without smoking).

Commercial jet fuel has a boiling range of about �90 °C–274 °C. Kerosene, with less-critical specifications, is used for lighting, heating, solvents and blending into diesel fuel.

Diesel oil

Diesel oil is used as fuel for diesel engines. Its ignition point is much higher than that of petrol.

Several grades of diesel fuel are manufactured — for example, ‘light-middle’ and ‘middle’ distillates for high-speed engines with frequent and wide variations in load and speed (such as trucks and automobiles) and ‘heavy’ distillates for low- and medium-speed engines with sustained loads and speeds (such as stationary engines).

Criteria for grading diesel oil include ease of ignition, ease of volatilization, and sulphur content. The highest grades, for automobile and truck engines, are the most volatile, while the lowest grades, for low-speed engines, are the least volatile, leave the most carbon residue, and commonly have the highest sulphur content.

Fuel oil

Fuel oil is used primarily for steam boilers in power stations, aboard ships and in industrial plants. Commercial fuel oils usually are blended with other petroleum fractions to produce the desired viscosity and flash point. Flash point is usually higher than that of kerosene.

47

Suggested Answers

Non-fuel products

Non-fuel use of petroleum is small compared with fuel use. A partial list of non-fuel uses for petroleum includes:

• solvents such as those used in paints, lacquers and printing inks;

• lubricating oils and greases for automobile engines and other machinery;

• paraffin wax used in candy making, packaging, candles, matches and polishes;

• petrolatum (petroleum jelly) sometimes blended with paraffin wax in medical products and toiletries;

• bitumen used to pave roads and airfields, to surface canals and reservoirs, and to make roofing materials and floor coverings;

• petroleum coke used as a raw material for many carbon and graphite products, including furnace electrodes and liners, and the anodes used in the production of aluminium.

Petrochemical industry

The petrochemical industry is a system of chemical processes that convert petroleum and natural gas into chemicals from which plastics and other synthetic materials can be made.

Primary petrochemicals are divided into three groups depending on their chemical structure:

• unsaturates — include ethene, propene, and butadiene;

• aromatic petrochemicals — include benzene, toluene, and xylenes;

• synthesis gas is a mixture of carbon monoxide and hydrogen.

48


Uses of ethene

Uses of benzene

Carbon dioxide and global warming

Carbon dioxide is the most important greenhouse gas. Over the past hundred years or so, humans have burnt large quantities of fossil fuels, putting much extra carbon dioxide into the atmosphere. This contributes to the enhanced greenhouse effect known as ‘global warming’.

Consequences of global warming on weather patterns

Warmer water in the oceans pumps more energy into tropical storms, making them stronger and potentially more destructive.

Warmer temperatures could increase the probability of drought. Greater evaporation, particularly during summer and fall, could exacerbate drought conditions and increase the risk of wildfires.

Warmer temperatures increase the energy of the climatic system and can lead to heavier rainfall in some areas.

Consequences of global warming on health

Hotter weather enables deadly mosquitoes to travel greater distances. More frequent and severe heat waves will result in a greater number of heat-related deaths.

Warming temperatures, alternating periods of drought and deluges, and ecosystem disruption have contributed to more widespread outbreaks of infections like malaria.

49

Suggested Answers

Consequences of global warming on wildlife

Rising temperatures ravage coral reefs and melt the habitats of polar bears and Antarctic penguins.

Consequences of global warming on glaciers and sea levels

Rising global temperatures will speed the melting of glaciers and icecaps and cause early ice thaw on rivers and lakes.

Sea levels will rise as a result both of thermal expansion of the oceans and melting of mountain glaciers and polar icecaps. Consequences include loss of coastal wetlands and barrier islands, and a greater risk of flooding in coastal communities. Low-lying areas are especially vulnerable.

Consequences of global warming on economy

Sea level rise and an increase in the severity of storms could put cities at greater risk of costly storm damage.

A study in 2007 found that global production of three out of the six major crops experienced significant losses due to global warming between �98� and 2002.

Global warming is forecast to inflict a variety of other costs, including declining rainfalls and rising temperatures that will combine to cause large and extended drought conditions, and impacts on public health due to heat-related illnesses.

Risks associated with the production, transportation, storage and use of fossil fuels

The burning of fossil fuels produces a variety of air pollutants. Carbon dioxide, a greenhouse gas that scientists believe is the key factor in global climate change, is also produced.

There are also environmental risks associated with extracting and transporting fossil fuels. Mining for coal and drilling for petroleum are especially hazardous because the digging of massive mines and wells can change the surrounding landscapes and bring massive amounts of salt water to the surface which can damage nearby ecosystems if there is no proper treatment against the waste water. Natural gas extraction is somewhat safer, but can also be hazardous. While there are regulations in place that attempts to minimize the risks, it is impossible to eliminate them completely.

Hazards associated with the use of household fuels

In Hong Kong, the most common household fuels are town gas and LPG (liquefied petroleum gas). Two potential hazards associated with these fuels are:

• carbon monoxide poisoning; and

• fires and explosions.

Carbon monoxide poisoning

Town gas contains a mixture of gases including hydrogen, carbon monoxide, methane and carbon dioxide. If there is a gas leakage, carbon monoxide will diffuse into the air.

Liquefied petroleum gas (LPG) contains mainly propane and butane liquefied under pressure. With sufficient supply of oxygen, LPG burns to form carbon dioxide and water.

When the supply of oxygen is insufficient, town gas or LPG burns incompletely. One of the products is carbon monoxide.

50


Carbon monoxide is a colourless, odourless and very poisonous gas. In very small amounts, it causes headaches and dizziness. It could be lethal if it is in large amount.

Fires and explosions

If a gaseous fuel leaks, it forms a mixture with the air. The mixture can be dangerously explosive. Many fires start at home because people are careless when using household fuels.

Safety precautions in using household fuels

Here are some safety precautions in using household fuels:

� When using gas burners in kitchens and bathrooms, open windows and doors to ensure good ventilation.

2 The rubber hose connecting the gas burner and the gas tap should be checked regularly by a qualified technician.

3 Place gas cookers away from windows so that wind cannot blow out the flame which leads to gas leakage. Also, place cookers away from flammable goods (e.g. window curtains).

4 Do not leave the house while a gas cooker is being used.

References (accessed August 20�4):

International Energy Agency (20��) ‘World Energy Outlook 20��’ (Paris: International Energy Agency), retrieved from http://www.iea.org/publications/freepublications/publication/WEO20��_WEB.pdf

Organization of the Petroleum Exporting Countries (20�2) ‘World Oil Outlook 20�2’ (Vienna: Organization of the Petroleum Exporting Countries), retrieved from http://www.opec.org/opec_web/static_files_project/media/downloads/publications/WOO20�2.pdf

http://elmhurst.edu/~chm/vchembook/325petrochem.html

http://global.britannica.com/EBchecked/topic/�6273�/diesel-fuel

http://global.britannica.com/EBchecked/topic/226565/gasoline

http://global.britannica.com/EBchecked/topic/454�99/petrochemical

http://www.arizonaenergy.org/News_09/News_Nov09/The%20High%20Cost%20of%20Fossil%20Fuels.htm

http://www.eia.gov/forecasts/ieo/index.cfm

http://www.elca.org/JLE/Articles/343

http://www.enviroliteracy.org/subcategory.php/2�.html

http://www.eoearth.org/view/article/�55206

http://www.gpca.org.ae/index.php

http://www.nrdc.org/globalwarming/

https://www.ic.gc.ca/eic/site/chemicals-chimiques.nsf/eng/bt0��35.html

http://resources.schoolscience.co.uk/SPE/knowl/4/2index.htm?knock.html

5�

Suggested Answers

Chemistry Magazine page 93

The fossil fuel dilemma

� Pros of using coal for generating electricity

• Coal energy is an affordable energy source because of coal’s stable price compared to petroleum.

• Coal is easy to burn.

• Coal produces a lot of energy upon combustion.

• Coal is abundant.

• Coal is a reliable energy source.

• Coal is widely distributed all over the world.

Cons of using coal for generating electricity

• Burning coal produces a large amount of carbon dioxide which leads to global warming and climate change.

• Burning coal produces air pollutants such as sulphur dioxide and oxides of nitrogen (that cause acid rain).

• Coal is non-renewable and fast depleting.

• Coal mining ruins the environment and puts the lives of people, especially the coal miners, in danger.

• The cost of coal storage is high, especially if enough stock for a few years is required to assure power production availability.

2 Pros of using wind power in Hong Kong

• Renewable energy resource

• Low air pollution

• Low water pollution

Cons of using wind power in Hong Kong

• Wind does not always blow. Alternative supplies are needed for ‘still days’.

• If the wind blow too hard, windmills may be severely damaged.

• Thousands of windmills are needed to provide enough electricity. Windy spots are often in beautiful areas. Windmills may become an eyesore.

• Possible noise pollution — the noise from wind farms is similar to the sound of a small jet engine.

• Wildlife can be endangered. Birds are known to try to fly between the running blades, and they get hit by the blades.

• Limited choice of suitable sites.

52



� a) alkanes

b) CnH2n+2

c) –ane

d) carbon dioxide

e) water

f) substitution

g) chloroalkanes

h) alkenes

i) CnH2n

j) –ene

k) addition

l) bromine

m) cold acidified dilute potassium permanganate solution

2 a) Cracking is the breaking down of larger hydrocarbon molecules with heat or catalyst to produce smaller hydrocarbon molecules.

b) • Producing extra petrol

• As a source of alkenes

c) C8H�8(l) C5H�2(l) + C3H6(g)

3 Any one of the following:

• Shake each hydrocarbon with an orange solution of bromine dissolved in an organic solvent.

The orange solution becomes colourless quickly when shaken with an unsaturated hydrocarbon.

There is no immediate observable change for a saturated hydrocarbon.

• Shake each hydrocarbon with cold acidified dilute potassium permanganate solution.

The purple solution becomes colourless quickly when shaken with an unsaturated hydrocarbon.

There is no observable change for a saturated hydrocarbon.

53

Suggested Answers

4 Across (accept other reasonable answers.)

4 saturated — to describe a hydrocarbon in which all the carbon atoms are connected to each other by single bonds

8 alkene —– homologous series with a general formula CnH2n

9 kerosene — a petroleum fraction used as fuel for aircraft

�0 ethanol — a member of the alkanol series

�4 petroleum — a fossil fuel formed from marine animals and plants that lived millions of years ago

�5 petrol — a petroleum fraction used as fuel for cars

�6 addition — a reaction in which two or more molecules react to give a single product

�7 ethene — the first member of the alkene series

Down (accept other reasonable answers.)

� butane — an alkane with a molecular formula C4H�0

2 coal — a fossil fuel formed from dead plant materials

3 hydrocarbon — an organic compound containing only atoms of carbon and hydrogen

5 bitumen — a petroleum fraction used to surface roads and roofs

6 alkane — homologous series with a general formula CnH2n+2

7 substitution — a reaction in which an atom (or group of atoms) in a molecule is replaced by another atom (or group of atoms)

�� naphtha — a petroleum fraction used to manufacture town gas

�2 cracking — the breaking down of larger hydrocarbon molecules with heat or catalyst to produce smaller hydrocarbon molecules

�3 methane — the first member of the alkane series

5 D

6 B

7 A

8 D

9 B

54


�0 D One possible cracking reaction of C8H�8 is shown below.

C8H�8(l) C6H�4(l) + C2H4(g)

The cracking of C8H�8 could NOT form heptane and ethene.

�� D Br

(in organic solvent)

(g) + Br2 (in organic solvent)C C

H

H

HC

H

H

C

H

H

H Br C

H

C

H

H

C

H

H

C

H

H

H

�2 D

�3 D (�) Ethane does NOT react with chlorine in the dark.

�4 C (�) Ethene and ethyne contain different functional groups. They belong to different homologous series.

(2) Both ethene and ethyne are unsaturated hydrocarbons. They can decolourize cold acidified dilute potassium permanganate solution.

(3) Ethyne has a higher carbon to hydrogen ratio than ethene. It is more difficult for ethyne to undergo complete combustion. Thus, it burns with a sootier flame than ethene.

�5 B (�) Both but-2-ene and but-�-ene have the molecular formula C4H8.

(2) But-2-ene is insoluble in water.

�6 B

�7 D (�) Ethane does NOT react with bromine in the dark.

(2) Ethene undergoes an addition reaction with bromine in the dark.

(3) There is NO reaction between ethene and acidified dilute potassium dichromate solution.

�8 a) Compound C contains a carbon-carbon double bond.

b) Compound D contains bromine atoms, not only atoms of carbon and hydrogen.

c) Name of homologous series: Alkane

General formula: CnH2n+2

d) The orange solution becomes colourless rapidly.

55

Suggested Answers

�9 a) i) A hydrocarbon is a compound that contains only atoms of carbon and hydrogen.

A hydrocarbon in which all the carbon atoms are connected to each other by single bonds is a saturated hydrocarbon.

ii) CnH2n+2

iii) C6H�4

b) i) 2C4H�0(g) + �3O2(g) 8CO2(g) + �0H2O(l)

ii) 2C4H�0(g) + 9O2(g) 8CO(g) + �0H2O(l)

iii) Supply of oxygen is insufficient.

c) i) The reddish brown bromine vapour changes to colourless gradually.

ii) Any one of the following equations:

The following reaction is responsible for the loss of the reddish brown colour of bromine:

C4H�0(g) + Br2(g) C4H9Br(l) + HBr(g)

However, the following reactions which lead to the formation of polysubstituted bromoalkanes, or other related reactions, are also reasonable answers.

C4H9Br(l) + Br2(g) C4H8Br2(l) + HBr(g)

C4H8Br2(l) + Br2(g) C4H7Br3(l) + HBr(g)

iii) Substitution reaction

20 Answers for the HKCEE question are not provided.

2� a) i) CH4

ii) C2H6

iii)

HH C

H H

C C

H

H H H

b) i) Alkane

ii) CnH2n+2


• Each member in a homologous series differs from the next by a –CH2– unit.

• They show a gradual change in physical properties.

• They show similar chemical properties.

56


c) i) C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l)

ii) Solid product: Carbon

Gaseous product: Carbon monoxide

d) i) Ultraviolet light

ii) Bromomethane

iii) CH4(g) + Br2(g) CH3Br(g) + HBr(g)

22 a) i) 2CH4(g) + 3O2(g) 2CO(g) + 4H2O(l)

ii) Insufficient oxygen / air


• Carbon monoxide formed is toxic.

• Less energy is produced.

• Unburnt hydrocarbons react further to form toxic / harmful products.

iv) Carbon dioxide formed is a greenhouse gas.

It can trap some of the infrared energy / heat radiated from the earth into the space. This leads to global warming.

b) i)

ii)

iii) Because a chlorine radical is regenerated by the propagation steps each time a molecule of the product is formed.

iv) CH3• + CH3• C2H6

57

Suggested Answers

23 a) The principle:

• The naphtha fraction has a different boiling point range when compared with other fractions.

• The sizes of the hydrocarbon molecules in the naphtha fraction are different from those in the other fractions.

The process:

• First heat the petroleum to about 400 °C in a furnace. Compounds with higher boiling points remain as liquid while those with lower boiling points vaporize. Thus, petroleum is turned into a mixture of liquid and vapour.

• Pass the mixture of liquid and vapour into a fractionating tower that is cooler at the top than at the bottom.

• The liquid flows to the bottom of the tower and is called the residue. The residue contains hydrocarbons with over 25 carbon atoms per molecule.

• The vapour cools down as it rises through the tower.

• When a substance in the vapour arrives at a height where the temperature of the tower is lower than the boiling point of that substance, it will condense to form a liquid.

• The trays collect the various liquid fractions. The liquid fraction that condenses on each tray is piped off.

• Hydrocarbons with smaller molecules have lower boiling points. Hence they condense in the trays nearer to the top of the tower, where it is cooler.

• Naphtha consists of molecules which are rather small. It is the liquid fraction of lowest boiling point range and thus is piped off from the upper part of the tower.

b) i) C�0H22 C6H�4 + 2C2H4

ii) Heat the naphtha fraction. The fraction vapourizes.

Pass the vapour over a catalyst.

iii) Ethene contains a carbon-carbon double bond, whereas there is no carbon-carbon double bond in alkanes. They have different functional groups.


25 a) Cracking is the breaking down of larger hydrocarbon molecules with heat or catalyst to produce smaller hydrocarbon molecules.

b) As a catalyst

c) The paraffin might vapourize and leave the boiling tube too quickly without undergoing the cracking process.

d) Because it is mainly air.

e) The gaseous product is insoluble in water because the product is collected in the test tube by displacement of water.

58


f) Remove the delivery tube from the water first.

To prevent water from sucking back.

g) Medicinal paraffin is a liquid while gas G is a gas.

Gas G has a lower boiling point and thus it should have a smaller relative molecular mass.

h) Fractional distillation

26 a) i) Saturated: All the carbon atoms are connected by single bonds.

Hydrocarbon: It contains only atoms of carbon and hydrogen.

ii) CnH2n+2

b) i) C5H�2(l) + 8O2(g) 5CO2(g) + 6H2O(l)

ii) The gas produced is a greenhouse gas which contributes to global warming.

c) Carbon

d) i) C9H20(l) C5H�2(l) + C4H8(g)

or C9H20(l) C5H�2(l) + 2C2H4(g)

ii) Plastics

iii) Because the bonds are strong.

27 a) The hydrocarbon molecules in petrol are smaller than those in fuel oil.

b) Any two from the following:

• Petrol is of higher demand / shorter supply.

• A higher tax is charged.

• Cracking is more expensive / uses more energy.

c) Fuel oil is heated in the presence of catalyst.

Larger hydrocarbon molecules are broken down to produce smaller hydrocarbon molecules.


29 a) CnH2n

b)

C

H

C

H

H

C H

H

C

H

H

H

59

Suggested Answers

c) i) The orange solution of bromine becomes colourless rapidly.

ii)

(in organic solvent)

(g) + Br2 (in organic solvent)

H

H

CH

H

Br

C

H

Br

C HC

H

C

H

H

H CH

H

iii) Addition reaction

d) i) The purple solution of potassium permanganate becomes colourless rapidly.

ii)

H(aq)CH3CH2 (g) + [O] + H2O(l) CH3CH2

H

O

C

H

O

H H

CC

H

CH

H

iii) Addition reaction


Practice

P28.1 page 112

a) Fractional distillation

b) Cracking of naphtha,

followed by fractional distillation of the mixture to obtain ethene.

c) i) H

H

C

H

H

C

ii) H

H

n C

H

H

C

n

H

H

C

H

H

C

iii) Additional polymerization

60


P28.2 page 116

� IUPAC name of monomer Structure of monomer Structure of polymer

ethene

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

tetrafluoroethene

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

1,1-dichloropropene

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

CH3

C

H

C

HH

H

C

H

C

HH

H

n

C

F

C

FF

F

C

H

Cl

C

Cl

CH3

C C

ClH

Cl

n

C C

FF

F F

n

2

CH

Ha)

H

C

H

C

H

C

H

H

H

CH

Hb)

H

C

H

H

C

H

C or C CH3C

H3C

H

H

H

H

c) But-2-ene:

CH3

CH3

C C

H

H

Alkene X:

CH2

C

H

CH3

C or

H

H

CH3

CH3

C C

H

H

6�

Suggested Answers

P28.3 page 120

� a) Plastic do not corrode.

b) Not suitable because PVC is a thermoplastic / softens upon heating.

2 a)

C

H

C

HH

OH

b) The polymer contains many –OH groups. Thus, it can form hydrogen bonds with water, facilitating its water solubility.

Discussion page 106

� • Electricity leakage can be prevented.

• Plastic does not corrode.

• Self-coloured / no painting required.

2 • Plastic does not corrode.

• No lubrication required.

• Quieter when slammed.

• Hard-wearing.

3 • Lightweight.

• Plastic does not corrode.

• No sharp edges.

62


Discussion page 112

ProductTwo properties the polymer

used should haveProduct

Two properties the polymer used should have

� Transparent pitcher

Any two of the following:• highly transparent• rigid• waterproof• easily shaped• chemically inert• non-toxic• does not flavour the water /

liquid

2 Milk feeding bottle

Any two of the following:• transparent• waterproof• can withstand the high

temperature of boiling water (as feeding bottles are usually sterilized by heating in boiling water)

• rigid• easily shaped• chemically inert• non-toxic• does not flavour the milk

3 Transparent chocolate case

Any two of the following:• transparent• hard• rigid• lightweight• easily shaped• non-toxic• does not flavour the chocolates

4 Bread bag Any two of the following:• good moisture barrier property• flexible• chemically inert• non-toxic• does not flavour the bread

5 Disposable foam cup

Any two of the following:• waterproof• can withstand the high

temperature of boiling water / liquid

• good heat insulating property• chemically inert• does not flavour the water /

liquid

6 Washing powder container

Any two of the following:• lightweight• durable• good moisture barrier property• easily coloured• does not deform under heavy

load / stiff

7 Zig-zag bag Any two of the following:• durable• flexible• good moisture barrier property• strong• chemically inert• non-toxic• does not flavour the food

8 Bottle crate Any two of the following:• durable • strong • lightweight • good resistance to chemical

attack • does not deform under heavy

load / stiff

9 Water pipe Any two of the following:• durable • corrosion resistant • easily shaped • chemically inert • non-toxic

�0 Shower curtain Any two of the following:• durable • easily coloured • flexible • does not wrinkle easily

63

Suggested Answers

Discussion page 119

ProductPolymer suitable for

manufacturing the productProperties of the chosen polymer

that make it suitable

� Transparent pitcher polystyrene or or Perspex Any two of the following:• highly transparent• rigid• waterproof• easily shaped• chemically inert• non-toxic• does not flavour the water / liquid

2 Milk feeding bottle polystyrene Any two of the following:• transparent• waterproof• can withstand the high temperature of boiling water

(as feeding bottles are usually sterilized by heating in boiling water)

• rigid• easily shaped• chemically inert• non-toxic• does not flavour the milk

3 Transparent chocolate case

polystyrene Any two of the following:• transparent• hard• rigid• lightweight• easily shaped• non-toxic• does not flavour the chocolates

4 Bread bag low density polythene Any two of the following:• good moisture barrier property• flexible• chemically inert• non-toxic• does not flavour the bread

5 Disposable foam cup expanded polystyrene Any two of the following:• waterproof• can withstand the high temperature of hot water /

liquid• good heat insulating property• chemically inert• does not flavour the water / liquid


64


ProductPolymer suitable for

manufacturing the productProperties of the chosen polymer

that make it suitable

6 Washing powder container

high density polythene Any two of the following:• lightweight• durable• good moisture barrier property• easily coloured• does not deform under heavy load / stiff

7 Zig-zag bag low density polythene Any two of the following:• durable• flexible• good moisture barrier property• strong• chemically inert• non-toxic• does not flavour the food

8 Bottle crate polypropene Any two of the following:• durable• strong• lightweight• good resistance to chemical attack• does not deform under heavy load / stiff

9 Water pipe polyvinyl chloride Any two of the following:• durable• corrosion resistant• easily shaped• chemically inert• non-toxic

�0 Shower curtain polyvinyl chloride with plasticizer

Any two of the following:• durable• easily coloured• flexible• does not wrinkle easily

65

Suggested Answers


� a) addition

b) addition

c) polythene

d) polypropene

e) polyvinyl chloride

f) polystyrene

g) Perspex

h)

CH3

CH3

C C

H H

HH

CH3

C C

H

HH

C C

H H

HCl

C C

H

HH

C C

C OH

O

H

i)

CH3

CH3

C C

H H

HH

CH3

C C

H

HH

C C

H H

HCl

C C

H

HH

C C

C OH

O

H

j)

CH3

CH3

C C

H H

HH

CH3

C C

H

HH

C C

H H

HCl

C C

H

HH

C C

C OH

O

H

k)

CH3

CH3

C C

H H

HH

CH3

C C

H

HH

C C

H H

HCl

C C

H

HH

C C

C OH

O

H

l)

CH3

CH3

C C

H H

HH

CH3

C C

H

HH

C C

H H

HCl

C C

H

HH

C C

C OH

O

H

66


2 a) A polymer is a compound which consists of very large molecules formed by joining together many small molecules repeatedly.

b) Addition polymerization is a reaction in which monomer molecules join together repeatedly to form polymer molecules.

No atoms are lost from the monomer molecules during the reaction.

c) A repeating unit is the fundamental part of a polymer molecule. Its structure is based on the structure of the monomer.

The whole polymer structure can be obtained by repeating the repeating unit.

3

ObjectSynthetic polymer

now usedOld material used

Advantages of using synthetic polymer

Disadvantages of using synthetic

polymer

Lenses perspex glass • lighter• not easily broken

• more easily scratched

Water pipes polyvinyl chloride iron • more durable• more corrosion

resistant• more easily

shaped• chemically inert

• less strong

Bucket polythene iron • lighter• more durable• more corrosion

resistant• more easily

shaped• chemically inert

• less strong• may deform

under heavy load

Packaging polythene paper • allow self-service shopping to develop and reduce the staff cost

• hygienic• convenient• fewer trees are

cut down• more durable• stronger• waterproof

• may flavour some foods

• potential source of non-biodegradable waste

Disposable cups polystyrene paper • fewer trees are cut down

• less easily damaged

• stiffer• better heat

insulating property

• more easily scratched

• toxic chemicals may be released when the temperature is too high

67

Suggested Answers

4

combustion

Process

a reaction which converts large alkane molecules into smaller alkane and alkene molecules

cracking a reaction which makes large molecules from many smaller molecules

fractional distillation the separation of a mixture of hydrocarbons

polymerizationa reaction in which carbon dioxide and water are made

Description

5 D The monomer of X is

H H

C C

CH3CH3

, but-2-ene.

6 D

7 B

8 D The monomer is

CH3 C2H5

C C

Cl H

, i.e.

Cl

.

9 B (2) NOT all thermoplastics are transparent.

�0 D

�� A

�2 B (�) The molecular formula of pent-�-ene is C5H�0 while that of methylbutane is C5H�2.

(2) Pent-�-ene undergoes addition polymerization as shown below:

n

C3H7

C C

H n

HC3H7

C C

H HH

H

(3) Pent-�-ene does NOT react with acidified potassium dichromate solution.

68


�3 B (�)

CH24CH3

CH3

C

H

C

Hparent chain containing 4 carbon atoms, with the carbon-carbon double bond between the first and second carbon atoms, i.e. but-1-ene

methyl group attached to the second carbon atom

1 2

3

\ the IUPAC name of the compound is 2-methylbut-�-ene.

(3) The compound undergoes addition polymerization as shown below.

n

CH3

C2H5

C C

H n

HCH3

C2H5

C C

H

H

�4 C Polymer X is Perspex.

(2) Perspex is strong and brittle.

�5 A (�) The following structures are possible:

H C

H

H

C

F

C

F

H H C

F

H

C

H

C

F

H H C

H

H

C

H

C

F

F

H C

F

H

C

F

C

H

H F C

F

H

C

H

C

H

H

F F

F F

(2) X can be an unsaturated compound.

(3) For example,

CH3

C C

H

FF

can undergo polymerization to produce a polymer with the repeating unit shown

below:

CH3

C C

H

FF

69

Suggested Answers

�6 a)

C C

HH

HCl

b)

C C

HH

HCl

c) Addition polymerization

d) Chloroethene is unsaturated because it contains carbon-carbon double bond.

Polychloroethene is saturated because all the carbon atoms are connected by single bonds only.

e)

CH C H

ClCl

HCl

�7 a)

C

O

CH3

H

C

H

H

C

O

H

C

H

H

C

O

H

C

H

C O

CH3

C O

CH3

C O

H

b) Addition polymerization

c) Vinyl acetate contains carbon-carbon double bond.

�8 Answers for the HKCEE question are not provided.

�9 a) i) Addition polymerization

ii) Name: Propene

Structural formula:

C

H

H

H

C

H

C

H

H

70



• Mix with bromine dissolved in an organic solvent.

The orange solution of bromine becomes colourless rapidly.

• Mix with cold acidified dilute potassium permanganate solution.

The purple solution of potassium permanganate becomes colourless rapidly.

20 a) E. It is insoluble in oil.

Its melting point is above �00 °C.

b) The intermolecular forces between the polymer chains are weak.

The chains can slide past each other easily.

c)

C

H

H Cl

C

H

n

2� a) Addition polymerization is a reaction in which monomer molecules join together repeatedly to form polymer molecules.


b)

C

Cl

H H

C

H

c) i) Any one of the following:

• bottles

• floor tiles

• shower curtains

• raincoats

• insulating tapes / coverings round electrical wires

• as ‘artificial leather’ in making seat coverings for taxis

ii) Any one of the following:

• drain pipes

• bottles

iii) No

PVC melts upon heating.

7�

Suggested Answers


b)

H C

H

C C

H

H

H

H

c) Part of the carbon-carbon double bonds of propene molecules is broken,

and the electrons in it are used to join the neighbouring molecules.

23 a) Good thermal insulator / low density

b)

CH2CH

n

c) A plastic that can be melted or softened by heat. / A plastic that can be remoulded when warmed.

24 a) Addition polymerization is a reaction in which monomer molecules join together repeatedly to form polymer molecules.


b) i) Polypropene

ii) Any two of the following:

• Strong

• Stiff

• Good resistance to chemical attack

• Non-toxic

• Does not crack when cold.

• Does not flavour the margarine.

c) i) A repeating unit is the fundamental part of a polymer molecule. Its structure is based on the structure of monomer.

The whole polymer structure can be obtained by repeating the repeating unit.

ii) CH3

CH3

C

H

H

C

C

O

O

72



• Does not break when hit.

• Does not corrode / does not react with moist air.

• Not degraded by sunlight.

• Does not dissolve in water.

• Non-biodegradable

• Lightweight

• Thermal insulator

• Durable

• High melting point

• Strong

• Rigid

d) i)

C

F

F

C

F

F

C

F

F

C

F

F

C

F

F

C

F

F

C

F

F

C

F

F

ii)

C

F

F

C

F

F


b) HDPE has a higher tensile strength. / HDPE is stronger.

c) Film and shelt for packaging / wrapping / grocery bag / squeezable bottle.

d) i) Polypropene

ii) Reason �: Does not dissolve in organic solvents.

Reason 2: Maximum operating temperature is above �20 °C.

73

Suggested Answers

pages 132–140Topic Exercise

� A Refinery gas is a gas while the others are liquids at room temperature and pressure. Thus, refinery gas has the lowest boiling point.

2 D

3 A

4 C

5 B

6 A

7 C

8 D

9 A

�0 B

�� B

�2 A

�3 D

�4 A

�5 D

�6 a) The petrol vaporizes and then the vapour condenses on the condenser and is collected in the conical flask finally.

Others are left in the original flask.

b) The process is continuous / constantly feed in crude oil and collect the petrol. This process involves automation. Less labour is required.

The huge fractionating tower can process large amount of petroleum at the same time which facilitates mass production.

74


c) i) Wear safety glasses / face masks / other correct precautions.

ii) No smoking / no naked flame / report spills / other correct precautions.

�7 Answers for the HKCEE question are not provided.

�8 a) More carbon dioxide is being released.

b) Any of the following answers are possible:

• Develop devices harnessing alternative energy sources (e.g. fuel cells powered by hydrogen or methanol of non-carbon dioxide releasing origins, solar panels).

• Develop more efficient engines for transport (e.g. hybrid engines, electric cars).

• Develop carbon capture and storage.

• Investigate the uses of carbon dioxide (e.g. in dry cleaning as a blowing agent / making decaffeinated coffee).

• Provide evidence to governments.

• Educate the society / produce documentaries.

• Monitor atmospheric changes.

c) Any one of the following:

Approving that the graphs provide reliable evidence that an increase in atmospheric carbon dioxide concentration will result in global warming

• The fluctuation of the curves on carbon dioxide concentration and on the change in temperature over the same period of the time is almost synchronic (assumed that the sources of data are reliable).

Disapproving that the graphs provide reliable evidence that an increase in atmospheric carbon dioxide concentration will result in global warming

• It is impossible to measure the exact average temperature years ago.

• There are other gases that may induce greenhouse effect.

�9 a) 2C�6H34(l) + 49O2(g) 32CO2(g) + 34H2O(l)

b) The fuel solidifies.

c) i) Equation: N2(g) + O2(g) 2NO(g)

Condition: Very high temperature

ii) Equation: 2NO(g) + 2CO(g) N2(g) + 2CO2(g)

Catalyst used: platinum / rhodium / palladium

iii) 4NO2(g) + 2H2O(l) + O2(g) 4HNO3(aq)

75

Suggested Answers

d) i) C�6H34(l) C6H�4(l) + 2C4H8(g) + C2H4(g)

or C�6H34(l) C6H�4(l) + C4H8(g) + 3C2H4(g)

ii) Plastics / polymers

20 a) Refinery gases have the lowest boiling point range.

b) i) Diesel

ii) Cracking breaks down larger hydrocarbon molecules with heat or catalyst to produce smaller hydrocarbon molecules.

Cracking converts fractions in excess to those in demand.

c) Octane contains only atoms of carbon and hydrogen.

2� a) Propane Propene

b) Percentage by mass of carbon in propene = 36.042.0

x �00% = 85.7%

c) Propene has a higher percentage of carbon by mass. Its possibility of undergoing incomplete combustion is higher,

carbon particles are produced in the process.


23 a) i) Hydrocarbon that does not contain benzene ring / aromatic structure.

ii) Fractional distillation

iii) C25H52 + 38 O2 25CO2 + 26H2O

b) i) Paraffin wax / C25H52

ii) Any two of the following:

Carbon monoxide / carbon / soot

c) C3H6

76


24 a) Any one of the following:

• Mix each hydrocarbon with bromine dissolved in an organic solvent separately.

The orange solution of bromine becomes colourless rapidly when mixed with hydrocarbon B.

The orange solution of bromine becomes colourless slowly when mixed with hydrocarbon A under sunlight.

• Mix each hydrocarbon with cold acidified dilute potassium permanganate solution separately.

The purple solution of potassium permanganate becomes colourless rapidly when mixed with hydrocarbon B.

There is no observable change for hydrocarbon A.

b) Alkenes

c)

C

H

H H

C

CH3

d) Polypropene

25 a) i) Petroleum

ii) Cracking is the breaking down of larger hydrocarbon molecules with heat or a catalyst to produce smaller hydrocarbon molecules.


Risk Amendment

Exposure to harmful / toxic fumes Set up the apparatus in a fume cupboard.

Escape of flammable / harmful / toxic reactants or products from the ill fitting bung

Fit the bung correctly.

Escape of flammable / harmful / toxic reactants or products from the poorly positioned delivery tube

Place the delivery tube below the month of the test tube.

Sucking back Remove the delivery tube from water before stopping heating.

b)

C6H5

C

H H H H

C

H C6H5 H

C C

77

Suggested Answers

26 a) Name of monomer: But-�-ene

Structure:

C2H5

C

H

C

HH

b) The polymer contains many –OH groups.

It can form hydrogen bonds with water.


28 a) A hydrocarbon is a compound that contain only atoms of carbon and hydrogen.

In a saturated hydrocarbon, all the carbon atoms are connected to each other by single bonds.

C8H�8 belongs to the alkanes homologous series.

b) The hydrocarbons in petroleum have different boiling points.

The boiling point of a hydrocarbon increases with the number of carbon atoms of the molecule.

A fractionating tower is cooler at the top than at the bottom.

Hydrocarbons with smaller molecules are collected at the top. /

Hydrocarbons with larger molecules are collected at the bottom.

c) i) Cracking is the breaking down of larger hydrocarbon molecules with heat or catalyst to product smaller hydrocarbon molecules.

ii) C�4H30(l) C8H�8(l) + C6H�2(l)

iii) Hydrocarbons with smaller molecules are in greater demand.

d) 2C8H�8(l) + �7O2(g) �6CO(g) + �8H2O(l)

e) i) Any one of the following:

Platinum / rhodium / palladium

ii) 2CO(g) + 2NO(g) 2CO2(g) + N2(g)

f) Water is a greenhouse gas.

78



30 a) Hydroxyl group

Carbon-carbon double bond

b) C5H�0O

c) i) The orange solution of bromine becomes colourless.

ii) C5H�0O + Br2 C5H�0OBr2

d) i) CH2

C

H H

C

CH2H3C OH

ii) You should:

• explain how hydrogen bonds from

• suggest why the polymer is soluble in water.

In your answer, you should make it clear how the structure of the polymer links to its solubility in water.

The hydrogen atoms of the –OH groups of the polymer have partial positive charges.

Hydrogen bonds form between these hydrogen atoms and the lone pairs on the highly electronegative oxygen atoms of water molecules.

OR

The hydrogen atoms of the water molecules have partical positive charges.

Hydrogen bonds form between these hydrogen atoms and the lone pairs on the highly electronegative oxygen atoms of the –OH groups of the polymer.

The polymer is soluble in water because it can form hydrogen bonds with water.

Documents

Suggested Teaching Scheme - STMGSSintranet.stmgss.edu.hk/~ted/ccy/new_edition/Book3Aanswer.pdf · Suggested teaching scheme for the curriculum ... source_phy/flash/ formation_e.html