Fuels

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TOPIC 5
Fuels
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Fuels

• A Fuel is a substance that produces Energy
  when burned.
• A good fuel releases its energy over a longer
  period of time
• A reaction in which energy is released is called
  an Exothermic reaction( a reaction in which heat
  is taken in called an Endothermic reaction).
• Another word for burning is Combustion ie.we
  combine the element with Oxygen gas

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Common fuels

• Most common household fuels contain the element
  Carbon.
• Fuels that contain carbon and hydrogen only are
  called Hydrocarbons.
• The simplest hydrocarbon is methane formula
  CH4.Methane makes up 96 of Natural Gas.

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Combustion of Hydrocarbons
Carbon dioxide is collected in the tube here. The
test for CO2 is that it turns limewater Milky(or
chalky)
Combustion of Methane gas
Water vapour from the burning methane gas
condenses here
All Hydrocarbons burn to give CO2
and H2O
Any substance that contains Carbon and Hydrogen
gives CO2 and H2O when burned
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Fossil Fuels
Fossil Fuels formed from living things millions
of years ago. There are three main Fossil Fuels
Coal
Oil
Gas
Coal was formed by the decay of vegetation which
was subjected to heat and pressure over a very
long period of time.
Gas was formed in much the same way as Oil. It is
often collected when drilling for oil.
Oil was formed by dead sea creatures falling to
the sea-bed where they were subjected to chemical
change by bacteria.
Fossil Fuels are Finite Fuels ie they will run
out in the future and cannot be regenerated.
Alternative sources of energy which are Renewable
must be found eg Solar, Wind Tide and Wave Power.
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Distillation of Crude Oil
Crude Oil is a mixture of Substances called
Fractions. To separate the fractions we heat them
until they boil off. This is known as Fractional
Distillation
The smaller fractions ie short carbon chains have
smaller Boiling Pts. and boil off first. The
smaller fractions are more flammable, lighter in
colour and less Viscous than the longer chain
Fractions
A Fractionating Tower
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Air Pollution

• When Carbon burns in plentiful supply of air it
  produces CO2

C O2
CO2
When Carbon burns in an insufficient supply of
oxygen it produces Carbon Monoxide
C O2
CO
CO is an odourless, poisonous gas which prevents
the blood absorbing Oxygen is therefore extremely
dangerous
The test for CO2 is that it turns limewater
milky(chalky)
CO2 extinguishes fires, whereas CO burns with a
blue flame. CO is neutral whereas, CO2 is Acidic
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Pollution from Cars

• The main pollutants from car exhausts are
• Unburned Hydrocarbons
• Carbon Monoxide
• Oxides of Nitrogen occurs in the
  Spark Plugs of petrol cars (not Diesel
  since they do not have spark plugs)

Cars have Catalytic Converters fitted to change
these to harmless gases CO2 and N2. Catalytic
converters are metal honeycombs coated in Platinum
Sulphur from petrol produces the acidic gas
Sulphur Dioxide(also a pollutant)when burned