1. No category

Topic 6
Unit 24
Suggested answers to in-text activities and unit-end exercises
In-text activities
Discussion (page 3)
1 Uses of coal:
• iron extraction — a blast furnace uses iron ore, coke (made from coal), and limestone;
• cement making — coal is an important source for the energy required 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 the manufacture of other chemicals, such as propane and butane.
Unit 24
• electricity generation;
Topic 6
2 This question helps to sensitize students’ awareness of the importance of fossil fuels in their daily lives.
Internet Search & Presentation (page 5)
Proved reserves of coal at the end of 2008
Region
Total (million tonnes)
Share of total
North America
246 097
29.8%
South & Central America
15 006
1.8%
Europe & Eurasia
272 246
33.0%
Middle East
1 386
0.2%
Africa
32 013
3.9%
Asia Pacific
259 253 (China 114 500)
31.4% (China 13.9%)
World total
826 001
100.0%
/
Topic 6
Unit 24
LN
Proved reserves of coal (thousand million tonnes)
Coal in China
China is the world’s biggest coal producer. Production has increased dramatically since the 1990s, part of China’s
rapid economic growth. Much of this coal is used internally for power generation and in making steel, but China
has also become a major exporter of coal.
The following map shows the coal bearing regions in China.
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Proved reserves of petroleum at the end of 2008
Total
(million tonnes)
Share of total
North America
9 700
5.7%
South & Central America
17 600
10.3%
Europe & Eurasia
19 200
11.2%
Middle East
102 000
59.8%
Africa
16 600
9.7%
Asia Pacific
5 600 (China 2 100)
3.3%
(China 1.2%)
World total
170 700
100.0%
Topic 6
Region
Unit 24
/
LN
Proved reserves of petroleum (thousand million tonnes)
Proved reserves of natural gas at the end of 2008
Region
Total (trillion cubic metres)
Share of total
North America
8.87
4.8%
South & Central America
7.31
4.0%
Europe & Eurasia
62.89
34.0%
Middle East
75.91
41.0%
Africa
14.65
7.9%
Topic 6
Asia Pacific
15.39 (China 2.46) World total
8.3% (China 1.3%)
185.02
100.0%
Unit 24
/
LN
Proved reserves of natural gas (trillion cubic metres)
Petroleum and natural gas in China
The distribution of China’s petroleum resources is located at Bohai Bay Basin, Sungliao Basin, Tarim Basin, Ordos
Basin, Junggar Basin, Pearl River Mouth Basin, Qaidam Basin and East China Sea Shelf Basin. For the natural gas,
the distribution is located in the Tarim Basin, Sichuan Basin, Ordos Basin, East China Sea Shelf Basin, Qaidam
Basin, Sungliao Basin, Yinggehai Basin, Qiongdongnan Basin and Bohai Bay Basin.
Geographically, over 70% of the minable petroleum resources are distributed at plains, shallow seas, stony desert
and desert. Over 70% of minable natural gas resources are distributed at shallow seas, deserts, mountains, plains
and stony desert.
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Petroleum and natural gas bearing regions in China
References:
http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/reports_and_publications/statistical_energy_
review_2008/STAGING/local_assets/2009_downloads/statistical_review_of_world_energy_full_report_2009.pdf
http://web.unbc.ca/~chenj/course/project/coal.ppt#256,1,Coal
http://161.207.1.13:82/gate/big5/news.cnpc.com.cn/system/2009/09/01/001256320.shtml
http://www.in-en.com/oil/html/oil-1607160742212212.html
Internet Search & Presentation (page 14)
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 world refinery production by products in 2007.
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Unit 24
Refinery gases
Refinery gases are used as feedstocks for petrochemical production processes. They are also used as fuels for
domestic heating and cooking.
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 100 should be fine.
The addition of tetraethyllead to retard the combustion was initiated in the 1930s but was discontinued in the
1980s because of the toxicity of the lead compounds discharged in the combustion products.
Petrol used in automobiles boils mainly between 30 °C and 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 190 °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 highspeed 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).
Topic 6
Unit 24
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.
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.
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Unit 24
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Unit 24
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References:
http://www.eoearth.org/article/Petroleum_refining
http://resources.schoolscience.co.uk/SPE/knowl/4/2index.htm?knock.html
http://www.britannica.com/EBchecked/topic/226565/gasoline
http://www.britannica.com/EBchecked/topic/162731/diesel-fuel
http://www.britannica.com/EBchecked/topic/454199/petrochemical
http://www.elmhurst.edu/~chm/vchembook/325petrochem.html
http://www.gpca.org.ae/overview.asp
Checkpoint (page 17)
1 To prevent excessive vaporization of petrol when it is used in car engines in hot regions, it must contain more
hydrocarbons with a greater number of carbon atoms in their molecules.
By contrast, to ensure adequate vaporization at low temperatures, petrol shipped to cold regions should contain
more hydrocarbons with a smaller number of carbon atoms in their molecules.
Petrol for
Number of carbon
atoms per molecule of
hydrocarbons
Ease of evaporation
Viscosity
Alaska in winter
smaller
easy to evaporate
easy to flow
Hong Kong in summer
greater
less easy to evaporate
less easy to flow
2 a) Fractional distillation
b)
A
B
C
D
–
–
–
–
refinery gases
petrol
kerosene
diesel oil
c)
A
B
C
D
–
–
–
–
as
as
as
as
gaseous fuel
fuel for cars
fuel for aircraft / domestic fuel
fuel for heavy vehicles / factories
d) Colour; ease of evaporation; viscosity; flammability; colour and sootiness of flame
e) Hydrocarbons in the different fractions contain different number of carbon atoms in the molecules.
Checkpoint (page 19)
Topic 6
1 2C4H10(g) + 13O2(g)
Unit 24
b) Exothermic
c) Endothermic
d) Exothermic
8CO2(g) + 10H2O(l)
2 a) Endothermic
Discussion (page 22)
1 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’.
2 Consequences of global warming on weather patterns
10
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.
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.
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 2007 study found that global production of three of the six largest global crops experienced significant
losses due to global warming between 1981 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 heatrelated illnesses.
References:
http://www.nrdc.org/globalWarming/fcons.as
http://www.elca.org/What-We-Believe/Social-Issues/Journal-of-Lutheran-Ethics/Issues/November-2009/EnergyDevelopment-and-Quality-of-Life-7.aspx
http://www.arizonaenergy.org/News_09/News_Nov09/The%20High%20Cost%20of%20Fossil%20Fuels.htm
Unit 24
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.
Topic 6
Checkpoint (page 22)
a) The Earth receives energy from sunlight and radiates energy back into the space. Greenhouse gases trap some
of the energy.
The heat trapped makes the Earth surface warm and suitable for supporting life.
b) Any one of the following:
• Respiration
• Burning fossil fuels
c) Photosynthesis
d) The remains / manure of cattles decay to give methane.
e) Any two of the following:
• Use alternative energy sources to generate electricity, e.g. nuclear energy, wind energy, solar energy,
hydroelectric power.
• Use hydrogen as fuel (in fuel cell) to power cars.
• Plant more trees.
f) Methane from biomass can be used as a fuel.
11
Checkpoint (page 28)
a) When incomplete combustion occurs, the carbon in the fuel / petrol forms carbon monoxide.
b) Inside a car engine, the air gets so hot that nitrogen and oxygen react together, forming oxides of
nitrogen.
N2(g) + O2(g)
2NO(g) + O2(g)
2NO(g)
2NO2(g)
c) i) Suspended particulates
Topic 6
ii) Irritate the respiratory system
d) Catalytic converter
Unit 24
Library Search & Presentation (page 29)
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 Internet Search & Presentation ‘Major uses of fractions of petroleum’ on
page 14 of the textbook.) 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.
(Refer to the detailed information under Discussion ‘Consequences of global warming’ on page 22 of the
12 textbook.)
References:
http://www.elca.org/What-We-Believe/Social-Issues/Journal-of-Lutheran-Ethics/Issues/November-2009/EnergyDevelopment-and-Quality-of-Life-7.aspx
STSE Connections (page 29)
1 a) i) Between 6 a.m. to 9 a.m.
ii) These times correspond to the morning rush hours, when traffic is at a peak.
b) i) NO
Topic 6
ii) This might suggest that NO is involved in ozone formation.
• Replace solvent-based paints with water-based paints.
• Avoid buying paints with labels indicating that their VOC contents will exceed the future limits prescribed
by the law.
• Avoid using VOC-containing products such as organic cleansing solvents and ask suppliers for non-VOC
or low-VOC alternatives, or products with a green label (e.g. awarded by Green Council).
• Store VOC-containing products in air-tight containers.
• Buy products with less packaging as the printing of packaging materials generates VOCs. • Avoid refuelling during hotter period of the day to minimize escape of petrol vapour due to petrol ‘cooking’
in the fuel tank.
• Drive less, share rides and use public transportation.
References:
http://www.epd.gov.hk/epd/english/environmentinhk/air/prob_solutions/vocs_smog.html#point_7
Unit 24
2 • Avoid using aerosol consumer products such as hairsprays, air fresheners, deodorants and insecticides that
often use VOCs as their propellants. Non-aerosol consumer products are usually in pump, solid, liquid, gel,
or roll-on forms.
13
Unit-end exercises (pages 34 – 41)
Answers for the HKCEE (Paper 1) and HKALE questions are not provided.
1
fossil fuels
are
petroleum
coal
natural gas
Topic 6
mainly composed of
is separated by
Unit 24
fractional
distillation
hydrocarbons
to give various fractions
that can be
divided into
three classes
alkanes
aromatic
cycloalkanes hydrocarbons
example
example
H
C
H
H
H
H
H
H
H
C
C
C
H
benzene
H
H
H
C
C
C
C
H
C
H
H
H
cyclopentane
H
C
H
benzene
H
H
H
H
H
H
H
C
C
C
C
C
C
C
H
H
H
H
H
H
H
heptane
14
H
C
H
C
H
C
H
H
C
H
C
C
H
H
cyclopentane
H
C
C
H
C
H
with properties
H
C
C
fractions containing
hydrocarbons with a
greater number of
carbon atoms in their
molecules
example
H
C
H
H
fractions containing
hydrocarbons with a
smaller number of
carbon atoms in their
molecules
with properties
1 lower boiling point range
1 higher boiling point range
2 lighter in colour
2 darker in colour
3 less viscous
3 more viscous
4 easier to evaporate (or more volatile)
4
5 more flammable
5 less flammable
6 burns with a clearer flame
6 burns with a sootier flame
H
more difficult to evaporate (or less volatile)
2
mainly
carbon
particles
major air
pollutants from
industry
include
include
a
poisonous
gas
carbon
monoxide
unburnt
hydrocarbons
oxides of
nitrogen
photochemical
smog
both
cause
Unit 24
together
produce
sulphur
dioxide
Topic 6
suspended
particulates
major air
pollutants from
motor vehicles
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
4 • As fuels for transportation
• As fuels for generating electricity
• As fuels for heating
• As raw materials in the petrochemical industry
5 Any four of the following:
• Carbon dioxide
• Methane
• Chlorofluorocarbons
• Oxides of nitrogen
• Ozone
6 C
15
7 D Options A, B and C — Boiling of water, evaporation of ethanol and sublimation of iodine all take in
heat.
Option D — The reaction of lime with dilute hydrochloric acid is a neutralization reaction. Heat is
released in the process.
8 D
Option
Pollutant
Effect
Topic 6
Unit 24
A
carbon monoxide
• a very poisonous gas
B
oxides of nitrogen
• irritate and attack the respiratory system and the lungs
• dissolve in rainwater to form acid rain
• give photochemical smog with unburnt hydrocarbons
C
sulphur dioxide
• irritates the respiratory system
• affects functioning of lungs
• dissolves in rainwater to form acid rain
D
unburnt hydrocarbons
• some hydrocarbons such as benzene may cause cancer
9 B
10 B
11 A (1) and (2) In a catalytic converter, nitrogen monoxide oxidizes carbon monoxide to carbon dioxide, and
it is reduced to nitrogen.
(3) The unburnt hydrocarbons are oxidized to water and carbon dioxide.
2C8H18(l) + 25O2(g)
Octane is used to represent a typical hydrocarbon in petrol.
2CO(g) + 2NO(g)
catalyst
catalyst
N2(g) + 2CO2(g)
16CO2(g) + 18H2O(l)
12 B
13 B (1) The boiling points of hydrocarbons A and B are both under 20 °C, i.e. they are gases at 20 °C.
(2) The boiling point of hydrocarbon C is NOT the lowest, i.e. it does NOT ignite most easily.
(3) Hydrocarbon D has the highest boiling point. Its molecules should have the greatest number of
carbon atoms.
14 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.
16
b) By fractional distillation
c) i) To avoid spilling if the apparatus is mishandled during assembly.
ii) To condense the various fractions obtained in the process.
iii) To measure the boiling point of the fraction coming out.
d) i) Fraction I
ii) Fraction IV
iii) Fraction I
iv) Fraction IV
15 a) Hydrocarbons are compounds that contain only carbon and hydrogen atoms.
Vapour of hydrocarbons with a smaller number of carbon atoms in their molecules condenses at lower
temperatures.
Vapour of hydrocarbons with a greater number of carbon atoms in their molecules condenses at higher
temperatures.
c) Kerosene
d) A fraction with a lower boiling point range contains hydrocarbons with a smaller number of carbon atoms
in their molecules.
e)
Unit 24
b) Petroleum is first heated to form vapour.
Topic 6
A fraction with a higher boiling point range contains hydrocarbons with a greater number of carbon atoms
in their molecules.
Name of fraction
Use
Refinery gases
as gaseous fuel
Petrol
as fuel for cars
Naphtha
manufacturing town gas
Kerosene
as fuel for aircraft / domestic fuel
Diesel oil
as fuel for heavy vehicles / factories
Fuel oil
as fuel for ships / power stations
16­ —
17 —
18 a) The damage might have been caused by acid rain.
The burning of fossil fuels produces various air pollutants, such as sulphur dioxide and nitrogen dioxide.
These pollutants react with rainwater to form acids that lower the pH value of rainwater. This gives rise
to acid rain.
2NO2(g) + H2O(l)
SO2(g) + H2O(l)
When these acids come into contact with stone building materials such as limestone, reactions occur. A
possible reaction is:
CaCO3(s) + 2HNO3(aq)
This reaction gradually breaks the stone structure.
HNO3(aq) + HNO2(aq)
H2SO3(aq)
Ca(NO3)2(aq) + H2O(l) + CO2(g)
17
b) Any two of the following:
• Impose tighter regulations on emissions from cars and industry.
• Encourage the use of mass transit to reduce vehicle emissions.
• Use alternative energy sources.
• Reduce exposure of the statue.
• Statue can be made of inert materials in the future.
19 —
Topic 6
20 —
Unit 24
18