FOSSIL FUEL COMBUSTION, Pollution & Climate
Brown's GCSE/IGCSE/O Level KS4 science-CHEMISTRY Revision Notes
Oil, useful products, environmental problems, introduction to
4. Burning fossil fuels - pollution, carbon monoxide, nitrogen oxides, what makes a good fuel?,
climate change and global warming
fossil fuels like coal, oil and natural gas are extremely useful important
sources of energy, the environment does pay a price, so it is important to
understand the sources and chemistry of pollution and how its effects can be
minimised. Pollutants from fossil fuel (coal, oil, gas etc.) burning in power stations and automobile
transport include carbon monoxide, sulfur oxides and nitrogen oxides and these
in turn through photochemical reactions can produce ozone and other harmful
irritant gases. Methods of reducing pollution are described ranging from
catalytic converters in cars to desulfurising oil based fuels and flue gases.
These notes on hydrocarbon fossil fuel combustion, and pollution & climate
change issues are designed to meet the highest standards of knowledge and
understanding required for students/pupils doing GCSE chemistry, IGCSE
Level chemistry and KS4 science courses.
Index of KS4 Science GCSE/IGCSE
Chemistry Oil & Organic Chemistry Pages: 1.
Fossil Fuels : 2. Fractional distillation of crude oil & uses of fractions : 3.
ALKANES - saturated hydrocarbons and combustion : 4.
Pollution, carbon monoxide, nitrogen oxides, what
makes a good fuel?, climate change-global warming :
5. Alkenes - unsaturated hydrocarbons :
6. Cracking - a problem of supply and demand, other products :
7. Polymers, plastics, uses and problems :
8. Introduction to Organic Chemistry - Why so many series of
organic compounds? : 9. Alcohols - Ethanol
- properties, reactions, biofuels :
10. Carboxylic acids and esters : 11. Condensation polymers, Nylon & Terylene,
comparing thermoplastics, fibres and thermosets
12. Natural Molecules - carbohydrates - sugars
- starch : 13. Amino acids, proteins,
enzymes & chromatography : 14. Oils, fats,
margarine and soaps :
15. Vitamins, drugs-analgesic medicines & food
additives and aspects of cooking chemistry! : 16. Ozone, CFC's and free
radicals : 17. Extra notes, ideas and links on
Global Warming and Climate Change : Multiple Choice and Gap-Fill Quizzes:
m/c QUIZ on Oil Products (GCSE/IGCSE easier-foundation-level)
m/c QUIZ on Oil Products (GCSE/IGCSE harder-higher-level) :
IGCSE/GCSE m/c QUIZ on other Aspects of Organic Chemistry
3 Easy linked GCSE/IGCSE Oil Products word-fill worksheets
ALL my Advanced
Level Organic Chemistry revision notes
4a. Atmospheric pollution: The Incomplete
Combustion of hydrocarbons
When fossil fuels burn
efficiently in an excess of air/oxygen the only products are
carbon dioxide and water e.g.
examples of complete
combustion burning are for example natural gas and petrol
methane + oxygen ==> water +
2O2(g) ==> CO2(g) + 2H2O(l)
pentane + oxygen ==> water +
8O2(g) ==> 5CO2(g) + 6H2O(l)
stations burn huge quantities of fossil fuels in the form of mainly coal, but
significant quantities of gas ans some oil. The heat from the very exothermic
combustion is used turn water into steam and steam driven turbines power the
electrical generators (very big dynamos!).
If there is not enough oxygen
present to completely burn the fuel to carbon dioxide and water other
products may form causing pollution and fuel inefficiency.
The most common partially burned products are likely to
be carbon C (soot) and deadly carbon monoxide CO.
fine black powder-dust is potentially harmful and readily formed in
fires i.e. its classically produced by smoky yellow flames and
inefficient motor vehicle engines.
like any fine solid 'dust' is harmful when absorbed on the sensitive
tissue of the linings of the nose, throat and lungs.
Soot deposits cause
coughing and sore throat and are ejected from your body through
sneezing, coughing, and nose blowing.
Coarse particles (10 microns) are
inhaled into your windpipe and settle there, causing irritation and more
Soot is also a 'carrier' of polycyclic aromatic
hydrocarbons (PAH's) on it which are carcinogenic.
Even very low
concentrations of carbon monoxide can be fatal. Why?
Oxygen is carried
around the body by a complicated protein molecule in red blood
cells called haemoglobin.
The bonding between oxygen and
haemoglobin is quite weak to allow easy oxygen transfer for
Unfortunately, the bonding between carbon
monoxide and haemoglobin is stronger, so oxygen is replaced by
carbon monoxide and blocks normal cell respiration.
consequences are reduced blood oxygen concentration leading to unconsciousness
This is why long road
tunnels are ventilated and you should never run a car engine in a closed
appear that the hydrogen in the fuel molecules is more easily burned and
usually forms water so the equations for incomplete combustion below show
the formation of carbon-soot and 'deadly' carbon monoxide when there is a
lack of oxygen for complete combustion. As mentioned already, soot
is obviously a 'dirty' pollutant coating any surface (including your
lungs!) that the soot particles settle on and they contain unburned
carcinogenic hydrocarbons AND carbon monoxide is involved in the
chemistry of photochemical smogs - so all in all, inefficient
combustion of fossil-hydrocarbon fuels is very undesirable!
There is also less heat released
in incomplete combustion compared to
complete combustion since not all the carbon atoms of the fuel are
fully combined with the maximum amount of oxygen.
it is extremely important that any combustion system is as efficient as
possible e.g. gas heaters, furnaces etc. must all have excellent ventilation
for complete combustion to harmless water and carbon dioxide.
If there is any smell
of gas, make sure (i) all appliances are turned off, (ii) all sources
of ignition are absent, and (iii) ring the gas board!
appliances have led to tragic deaths. Carbon
monoxide is colourless and odourless
and even low concentrations in the air
can be fatal. It also accounts for why
long road tunnels need to be well ventilated too.
Carbon monoxide is unfortunately
emitted by all car exhausts, though catalytic converters help
reduce this by converting nitrogen monoxide (another pollutant) and carbon
monoxide into harmless nitrogen and carbon dioxide.
2CO(g) ==> N2(g) + 2CO2(g)
like platinum and rhodium are used in the catalytic converter.
NO, is formed by the combination of nitrogen and oxygen at high
temperature in automobile engines (cars, lorries, buses etc. - its
all the same!)
O2(g) ==> 2NO(g)
readily forms nitrogen dioxide by combining with oxygen in air on
exit from the engine exhaust.
O2(g) ==> 2NO2(g)
Nitrogen dioxide is a
lung and eye irritant, and, along with nitrogen monoxide, it is
involved in the complex chemistry of photochemical smogs which can
also produce ozone and other harmful chemicals in the air.
The reduction of fossil
fuel burning is the only way to reduce photochemical smog e.g. using
photovoltaic cells to harness solar energy to produce electricity.
Using solar power indirectly in this way to run electric cars is
potentially a good partial solution to the problem.
pollution problems of plastics
4b. Energy resource evaluation
- What makes a good
It may seem a curious question these
some fossil fuels pollute more than others, and some leave a bigger
Factors that should
be taken into consideration - often factors overlap
kJ of heat energy released per kg;
Geographical convenience - is it imported?, fluctuations in oil production levels
and the market price
and safety issues e.g. coal very safe, natural gas (explosive
flammable gas) much more dangerous to store, but the gas is easy and
more convenient to distribute via pipes.
Costs of exploration and
extraction can be high for oil
Coal mines are dangerous
to operate, good health and safety policies don't come cheaply, and
its the same for operating oilfields and petrochemical complexes -
Costs of transporting
AND even after
considering all of these factors ...
and climate change:
Greenhouse effect - which
fuel produces the least or most carbon dioxide for the energy
released?, methane is one of the best fossil fuels in this respect.
The sulphur content of fuel (most removed before fuel used to minimise
sulphur dioxide and acid rain formation), some coals are very high
The efficiency of combustion e.g.
minimum carbon monoxide and soot levels, again methane is one of the
most clean burning fuels.
Ease of use:
Transferred easily e.g. oil and gas readily piped around and readily
ignited for a quick start in power station. Coal is more trouble to
transport and does not ignite as easily.
also on OP02
More on "What is produced when
organic compounds are burned"?
Some organic compounds are used as fuels.
Other organic compounds, including plastics, are
burned as waste. Burning these organic compounds releases gases into the
organic compounds consist partly of
carbon atoms and many contain hydrogen and other atoms such as oxygen and
nitrogen. Coal, crude oil, natural gas (methane) and wood
contain organic compounds
- all are used as fuels, either directly
like coal or natural gas,
- or indirectly as coke from coal or
petrol from crude oil etc.,
- and apart from wood, they are finite
(limited reserve) fossil (from decayed organic material) fuels.
- Many hydrocarbons are fuels
substance burned to release heat energy.
- When organic compounds are burned in a
plentiful supply of air the carbon is oxidised to carbon dioxide and the hydrogen
is oxidised to water.
- In a limited supply of air incomplete combustion
occurs forming carbon monoxide and/ or carbon.
- Carbon monoxide is
poisonous because it reduces the capacity of blood to carry oxygen.
- Combustion equations and tests for combustion products
are all on the Oil Notes
web page, lots of examples and diagrams too.
- Each fossil fuel has a different cost, efficiency and cleanliness
on burning. Generally speaking in 'cleanliness' the order is methane
(natural gas) > alkanes in petrol > heavy oil and from left
to right there is also an increase in C/H atom ratio in the molecule so
more CO2 produced too. Some
on other fuels (but they were designed for more advanced level
courses) and a fossil
fuel properties survey above.
- The combustion of plastics
(and other organic compounds) which
contain chlorine and nitrogen produce poisonous fumes when burnt e.g.
chloride HCl and toxic hydrogen cyanide HCN respectively. Especially where there is a
limited supply of air. The combustion products of carbon (toxic CO and CO2)
and hydrogen (H2O) are
aspects of the Petrochemical Industry
Products and Environment Problems & what can we can?
(see also plastics)
'COSTS'?: Our economy, like many
other countries has become very dependent on the extraction, sale and
use of oil based products. BUT, there is high price to be paid at
times whether it be pollution effects or warring countries with oil
ACCIDENTS: Oil rig accidents,
broken pipelines, oil tanker wrecks etc. all have terrible effects on the
plant and animal life of the locality as we see from the horrible TV pictures of
seabirds coated in oil, and toxic oil slicks covering the beaches and
Birds get poisoned when
trying to clean themselves and other animals like sea otters, whales can
be poisoned too.
In fact the whole marine
ecosystem of an area can be devastated so that even creatures not
directly poisoned can be affected if their food chain is disrupted.
There is also the risk to humans from fires and explosions on
rigs or at oil refinery installations and fuel storage depots etc.
RISING CARBON DIOXIDE LEVELS - greenhouse gases -
climate change - global warming
The graph shows the
steady rise in the concentration of carbon dioxide in the atmosphere
from 1959-2004 as measured at the Mauna Loa mountain top observatory on
the Pacific island of Hawaii.
In 2012 the carbon
dioxide concentration in the air has reached 400 ppm.
This represents the highest
carbon dioxide levels in the atmosphere for at least 250,000 years. This
is known because trapped air bubbles in ice cores from the arctic
regions can be analysed to obtain their % composition. Every year snow
falls form a new layer that become compacted into thin layers of ice
which become buried beneath successive yearly precipitations so a long
geological record of the earth's atmosphere is preserved.
It is a good
base-line for our planet because it is well away from any industry
involving fossil fuel burning.
The concentration of
CO2 is in ppm (parts per million).
1ppm means 1 in 106
of air molecules is CO2. In % volume terms, 1 ppm = 100 x 1 /
106 = 0.0001%.
The graph shows that
the CO2 has risen from 0.0316% (316 ppm) in 1959 to 0.0378%
(378 ppm) in 2004.
This doesn't seem
much of an increase, BUT on a global scale, the extra 'Greenhouse CO2
Gas' could have drastic consequences (see next paragraph), but the
computer model predictions have a high degree of uncertainty.
I've started a new
page of extra material including graphs, explanations and discussion points
The burning of oil and
other fossil fuels is believed to be contributing to the 'Greenhouse
The Earth's land-water surfaces absorbs the Sun's
radiation in the form of infra-red (main heating effect) and
The infrared light
re-emitted from the warmed earth's surface is absorbed by gases like
carbon dioxide, and the absorbed energy causes the rise in temperature.
Carbon dioxide from fossil fuel
burning, and other gases
including methane, water vapour and CFC's absorb the re-radiated
lower frequency infrared energy from the Earth's surface and so warming the
atmosphere, rather like a greenhouse allows the sunlight in but not
out. The effects are predicted
to be dramatic e.g. rising sea
levels as polar ice melts causing flooding in low lying land,
more energy in the global weather system leads to more frequent
violent weather patterns etc. etc.
further note from IPCC report
2007) BUT there is considerable
uncertainty as to what might actually happen, but the consensus
amongst scientists is that fossil fuel burning is raising the global temperature
by a small, but not insignificant amount.
What can we do
about it? i.e. how can we reduce our 'carbon footprint' to reduce global
amount of fossil fuels we burn in power stations, but the
international community is struggles to come to an agreement over this
issue and the huge, and fast growing economies of India and China are
demanding the building of large numbers of fossil fuel power stations
(in 2006 China is starting to build one every week!).
alternative renewable energy resources can be more exploited,
but not without problems e.g.
wind turbines -
power - subject to storm damage
damming the exit
from a valley or canyon, but who wants their valley flooded!
a large tidal
barrage across a river estuary, but what about
environmental-ecological effects, and possible silting up.
photovoltaic cells -
depends on intensity of sunlight and varies from country to
country, through the day and the seasons
solar power panels in roofs etc.
- comments as above!
reduce acid rain pollution and CO2 production by using less
good for domestic and small communities but only nuclear power and
large scale hydroelectric power schemes are
suitable for large scale energy production for the highly populated
countries with large industrial economies.
Like 2., nuclear power is another option that does not produce carbon dioxide
and is suitable for large scale power generation, but there are real
public fears about the safety of nuclear power generation 'fuelled' by
the consequences of the nuclear power plant accident
at Chernobyl, in the Ukraine in 1986. It is extremely costly to build
nuclear power stations and there are added extra long term costs in
decommissioning nuclear power stations, safely processing the waste
and safely storing the residual radioactive waste for hundreds to
thousands of years.
include storing the CO2 from fossil fuel power stations
underground in rocks under pressure - but I don't know any details
or how feasible it is.
electricity and heat energy from fuel combustion by being careful
of its use e.g. increase home insulation and more efficient electrical
appliances like 'low energy' light bulbs.
Burning wood is
sustainable and the CO2 formed on its combustion is
recycled via photosynthesis BUT (i) it does not burn cleanly, (ii) its
energy density is low (heat energy released per mass of fuel) and
(iii) no good for large scale power generation.
This makes the predictions about global warming even more uncertain.
As the earth warms up, more
water vapour can exist in the atmosphere.
The more cloud that is formed in the upper atmosphere the more
sunlight is reflected, so less radiated energy reaches the Earth's
surface, leading to the opposite of global warming.
It has been
suggested that cloud formation could be encouraged by seeding the
atmosphere with crystals to promote cloud formation.
It is ironic
that the vapour trails of aircraft, with their heavy use of fossil
fuels, actually contribute to global dimming as well as to global
warming at the same time!
The effect of global dimming was noticed
in the aftermath of the 9/11 terrorist attacks on New York's World Trade Center
Twin Towers in 2001.
aircraft were grounded in the USA and many parts of the world for several days
after the attacks and
sunlight gauges showed a small but abnormal increase in sunlight levels
reaching the Earth's surface.
It is believed that
small (fine) solid particles like soot/carbon or ash in the atmosphere can cause global dimming
because they form the nuclei of water condensation producing the fine
water drops of clouds.
ACID RAIN: Fossil fuels contain
compounds of the
element sulphur When the fuel is burned the sulphur
compounds also burn
to form sulphur dioxide. This is
an acidic gas and dissolves in
rainwater, it then reacts with water and oxygen to form a very dilute solution of sulphuric
sulphur + oxygen ==>
Sulphur dioxide is
a harmful gas and lung irritant and contributed to 5000 extra
deaths in the great 'London Smog' in the 1950's as well as being a
major acid-rain gas.
Sulfur dioxide reacts with oxygen (in air) and water
(rain) and gets oxidised to form very dilute sulphuric acid - the
origin of acid
rain, and the overall change is represented by the equation below.
+ O2(g-air) + 2H2O(l-rain) ==>
The formation of acid
rain has several bad effects on the environment e.g.
the low pH causes plant damage, particularly
life forms and so damages eco
cycles and food chains in rivers or lakes harming wildlife like trout,
'weathering' corrosion rates of building stone and statues (particularly
those made of limestone).
All fuels are
processed at the oil refinery to reduce the concentration of
sulfur/sulphur compounds (the process of
desulfurisation/desulphurisation) but this adds to the cost and not
all the sulphur/sulfur is removed.
However, low sulfur
content petrol and diesel are being introduced.
Of course, the less
fossil fuels we burn, the less pollution results, so strategies to
design more efficient road vehicles, using less energy in the home,
renewable energy resources etc. will all help in the long run to
Power stations can be
fitted acid gas scrubbers eg removing the acidic sulfur
dioxide with an alkaline mixture of water mixed with powdered
POLLUTANTS: High temperature
combustion also produces other pollutants including ...
collectively denoted by NOx:
NO is formed in car engines and changes to NO2,
which is acidic, contributing further to acid rain (above), and
are also involved in the chemistry of 'photochemical smog'
- which produces chemicals harmful to respiration, irritating to
eyes and contributes to acid rain. Many
of the reactions are initiated by sunlight.
is formed in high temperature combustion situations e.g. car
engines, power station furnace burning coal, oil or natural
and in air the
nitrogen monoxide rapidly combines with the oxygen in air
dioxide is oxidised to nitric acid by the reaction with oxygen
from air when it dissolves in rainwater.
Carbon monoxide CO,
which is toxic, and also involved in the chemistry of
'photochemical smog' (see 4a). This is formed by inefficient combustion
hydrocarbons, CxHy, which can be
carcinogenic and are also involved in photochemical smog
converters* can significantly reduced these three unwanted
emissions (see above for
CO and NO removal, and CxHy gets
oxidised to CO2 and H2O). * e.g. using
platinum-rhodium transition metal catalysts, these are
dispersed on ceramic bed to give a big surface area for the
best reaction rate.
There are other indirect
pollution problems to do with burning fossil fuels:
Lead compounds are
added to petrol to improve engine performance.
Photochemical smog is
mentioned in the previous paragraph.
4e. Alternative fuels to fossil fuels
- more on other energy resources
OIL IS A VALUABLE
Apart from the obvious value
of crude oil as an non-renewable energy source, should we
using this very valuable source of organic chemicals by merely burning
most of it?
AND how long will oil reserves
AND what happens if
the oil runs out?
Therefore isn't it in our
own interest to manage the finite oil reserves remaining and conserve
AND seek other sources of
energy to power our lives?
AND perhaps influence the
course of global warming?
BUT the trouble is, oil is
very convenient, readily available, and new reserves are still being
found and the oil and gas trapped in deep layers of shale are being
AND it will take time to
develop new technologies.
It should be noted that
liquid fuels like petrol, diesel, central heating oil etc. are east to
store and distribute to wherever they are need in homes or factories and
they are so readily available, that change may be necessary, but
progress will be slow.
HYDROGEN - FUEL
of the FUTURE?:
can be used as fuel and a long-term possible alternative to fossil
It burns with
a pale blue flame in air reacting with oxygen to be oxidised to
It is a
non-polluting clean fuel since the only combustion product is
water and so its use would not lead to all environmental problems
associated with burning fossil fuels.
It is easily
distributed in pipes like natural gas, but there are health and safety
issues to do with storage and distribution since it is, like natural
gas, highly flammable and explosive.
It would be
ideal if it could be manufactured by electrolysis of water e.g.
using solar voltaic-cells or some kind of but the technology is in
be used to power
cells see the "Extra Electrochemistry" page
renewable fuels are discussed on other pages ...
Multiple Choice Quizzes and Worksheets
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products
KS4 Science GCSE/IGCSE m/c QUIZ on other aspects of Organic Chemistry
3 linked easy Oil Products gap-fill quiz worksheets
ALSO gap-fill ('word-fill') exercises
originally written for ...
... AQA GCSE Science
Useful products from
crude oil AND
... OCR 21st C GCSE Science
Worksheet gap-fill C1.1c Air
pollutants etc ...
... Edexcel 360 GCSE Science
Crude Oil and its Fractional distillation
... each set are interlinked,
so clicking on one of the above leads to a sequence of several quizzes
ALL my Advanced
Level Organic Chemistry revision notes
Notes information to help revise
KS4 Science Additional Science Triple Award Separate Sciences Chemistry revision
notes for GCSE/IGCSE/O level Chemistry Revision-Information Study Notes for
revising AQA GCSE Science AQA GCSE Chemistry, Edexcel
GCSE Science, Edexcel GCSE Chemistry, OCR 21st Century Science Chemistry, OCR Gateway Science
GCSE science-chemistry CCEA/CEA GCSE science-chemistry
(and courses equal to US grades 8, 9, 10)
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