4A Fossil fuel air pollution - incomplete combustion,
pollution from carbon
monoxide, particulates and soot
Anthropogenic means any
environmental change or pollution due to human activity
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4B Pollution, Accidents
and Economic Aspects of the Petrochemical Industry
Greenhouse effect, global warming, climate change,
carbon footprint from fossil fuel burning
4D Fossil fuel air pollution - effects of sulfur oxides
and nitrogen oxides
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4A Atmospheric pollution: The Incomplete
Combustion of hydrocarbons and
Carbon dioxide, carbon monoxide, soot,
water vapour, sulfur dioxide and oxides of nitrogen
are all produced in the combustion of fossil fuels.
Carbon dioxide and water vapour are the main 'greenhouse gases'.
INTRODUCTION - burning fossil fuels
POLLUTION - soot particulates and carbon monoxide
There are good reasons why
we should do our best to control atmospheric pollution - pollutants build up and create environmental problems for most
plants and animals, particularly in the air of
many of the world's cities causing ill-health e.g
respiratory diseases like asthma and other respiratory conditions.
To reduce pollution (and global warming
too!) we need to burn less fossil fuels and develop other 'greener
Sources and pollution problems due to
incomplete combustion e.g. soot, particulates and carbon monoxide are
Pollution and health problems from sulfur
oxides and nitrogen oxides are dealt with in section 4D Fossil
fuel pollution and effects from sulfur oxides and nitrogen oxides
- Starting with coal combustion, then
onto burning hydrocarbons and pollution
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 3.
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.
- 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
The fuel coal
consists mainly of carbon, which, if burned/ignited in excess air,
combusts to form carbon dioxide.
carbon + oxygen
====> carbon dioxide
+ O2(g) ====> CO2(g)
This is what you
expect to happen in an open domestic coal fire.
If not enough
air/oxygen is available, coal will only 'half' burn to form the deadly
odourless, colourless and toxic gas carbon monoxide.
+ O2(g) ====> 2CO(g)
This can happen
if organic material, coal or peat or any combustible material is smouldering underground and is
obviously a dangerous situation.
If it was formed
in a domestic coal fire it will quite happily burn with a pale blue
flame to form the 'safe' combustion product carbon dioxide gas.
+ O2(g) ====> 2CO2(g)
However in house fires, there
tends to be a lack of oxygen and fumes of smoke and carbon monoxide
are formed, which probably causes more deaths in fires than being
When fossil fuels burn
efficiently in an excess of air/oxygen the main products are
carbon dioxide and water e.g.
examples of complete
combustion burning are for example natural gas and petrol
stations burn huge quantities of fossil fuels in the form of mainly coal, but
significant quantities of gas and 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!).
CARBON MONOXIDE, soot and hydrocarbon particulates
and incomplete combustion
monoxide is a toxic gas and unfortunately it is colourless and
odourless and so not easily detected.
Carbon monoxide combines with
haemoglobin in the blood, reducing its capacity to carry oxygen.
CO molecules will displace O2 oxygen molecules from haemoglobin depriving cells of
the essential oxidant O2 !
Lack of oxygen can lead to
feeling weak, fainting and reduction of brain function. If you
breath in more than traces over a period of time you can go into a
coma and death - CO is pretty toxic and lethal dose isn't that high!
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.
This is referred to as
Visually, blue flames
indicate complete combustion releasing lots of heat energy, but smokey
yellow flames indicate incomplete combustion releasing less energy.
The most common partially burned products are likely to
be carbon C (soot) and deadly carbon monoxide CO.
A simplified word
equation covering most possibilities is ...
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.
Black sooty marks
indicate incomplete combustion and soot deposits cause
coughing and sore throat and are ejected from your body through
sneezing, coughing, and nose blowing. Respiratory problems can follow.
Coarse solid particles (10 microns
in diameter) are
inhaled into your windpipe and settle there, causing irritation and more
coughing and ultimately lung damage.
Soot particles also are 'carriers' of polycyclic aromatic
hydrocarbons (PAH's) on it which are carcinogenic molecules (cause DNA
damage - cancer forming) of general
formula CxHy, where x and y are at
These are examples of unburned hydrocarbons which are emitted from vehicle
exhausts as particulates, especially from diesel engines (much
more so than emissions from petrol engines).
These fine particles of
soot and hydrocarbons are called particulates, they
reduce air quality and are
known to cause health problems, particularly with our
Particulates are also
believed to cause a phenomena known as 'global dimming',
because they scatter sunlight and cause a cooling effect.
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, particularly
affecting the brain, and can lead to fainting-unconsciousness, a
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
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.
Particulate carbon doesn't
get the headlines like acid rain, but it is a serious problem that
you get from burning coal and diesel fuel too.
As mentioned already, soot
is obviously a 'dirty' pollutant coating any surface (including your
lungs!) that the soot particles settle on - dark colouration on
buildings from the Industrial Revolution the emergence of steam
powered Victorian technology.
Soot particles of carbon
also 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!
Incomplete combustion is still
exothermic, but 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.
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 to avoid any toxic
Hot water heaters, gas
fires and central heating boilers, should all be regularly serviced
to ensure they burn efficiently and not produce any potentially
harmful levels of toxic carbon monoxide.
All gas fired appliances
CARBON MONOXIDE - catalytic removal
(more on catalytic converters in section 4D)
Carbon monoxide is unfortunately
emitted by all car exhausts, though catalytic converters help
reduce this by converting nitrogen monoxide (another pollutant,
See oxides of nitrogen pollution) 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
which can remove over 90% of the harmful gases.
NO, is formed by the combination of nitrogen and oxygen at high
temperature (up to 1000oC) in automobile engines (cars, lorries, buses etc. - its
all the same!)
O2(g) ====> 2NO(g)
readily forms nitrogen dioxide (nitrogen(IV) oxide) 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.
For other notes on nitrogen oxides see Fossil fuel air pollution - effects of sulfur oxides
and nitrogen oxides notes
pollution problems of burning plastics
PLEASE READ CAREFULLY - from an article by George Monbiot "What car fumes do to
Other useful pages
Multiple Choice Quizzes and Worksheets
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (easier-foundation-level)
KS4 Science GCSE/IGCSE m/c QUIZ on Oil Products (harder-higher-level)
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 ...
... Ex AQA GCSE Science
Useful products from crude oil
Oil, Hydrocarbons & Cracking
OCR 21st C GCSE Science
Worksheet gap-fill C1.1c Air pollutants
... Edexcel 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
keywords and phrases:
revision study notes for 14-16 school chemistry AQA Edexcel OCR IGCSE/GCSE
9-1 chemistry science topics modules for studying use of catalytic
converter to control air pollution, effects of incomplete combustion of
fossil fuels, carbon particulates, carbon monoxide poisoning, pollution and
harmful effects from soot particulates breathed into your lungs gcse
chemistry revision notes igcse revising KS4 science
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