The properties of
petrol (gasoline), kerosene and diesel
What you already know: How these fuels are derived from
mineral oil and the differences in their molecular structure
and boiling points.
Just to check, fill in the missing data in the following table:
Kind of fuel
Gasoline
Kerosene
Diesel
Light fuel oil
1
Boiling range
What you are now going to find out: How the different
molecular structures of various forms of petrol, of kerosene
and of diesel affect their other properties.
1)
2)
3)
4)
Size of molecules1
Number of Carbon-atoms
Next, give some constitution formulae (at least 3 per fuel) of
compounds that are contained in these fuels. (Best use the
type consisting only of C-C-bonds).
What is the difference between open-chain and cyclic
saturated hydrocarbons? – What are isomers?
Work sheet: Mineral oil based fuels
Now make sure that you know, how the three types of
engines (petrol-motor, jet engine, diesel-motor) work! You
might consult the following link:
http://auto.howstuffworks.com/engine.htm
Melting ranges of gasoline and diesel
Flammability of gasoline and diesel
Difference between high and low octane gasoline
Aromatic hydrocarbons in gasoline
Ad 1) If your family owns a car with a diesel-engine, you
might have encountered the situation that the car did not
work on account of the cold on a day with temperatures far
below zero.
What you need:
Petrol and light fuel oil (just a
few millilitres), test tubes, a
thermometer, ice, salt and a
basin
Put crushed ice into the basin
and prepare a freezing mixture
by adding copious amounts of
salt. The temperature should fall
to approximately -20°. Then stick two test tubes – one filled
with gasoline the other with diesel – into it. – What do you
observe?
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What is the reason for taking light fuel oil instead of diesel?
– Diesel contains additives that are harmful, so that you
should avoid inhaling it or letting it get into contact with
your skin! (Keep this in mind, when refuelling your(?) car at
the service station!)
Ad 2) You ought to know that petrol must not ignite by itself
in the petrol-engine, while diesel in the diesel-motor has to
do so to guarantee its function. Therefore one might assume
that diesel can be ignited more easily than petrol.
Let’s check!
You need:
Petrol and light fuel oil or
liquid paraffin, two porcelain
pots
and
matches
(preferably long ones!) – but
there is no need to use a
burner. Safety goggles
and protection gloves!
surface of the liquids.
What do you observe?
Fill a few millilitres of the
two fuels into separate pots,
put them apart by some
thirty centimetres and hold
a burning match above the
………………………………………………………………………………………………….
Please explain!
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Work sheet: Mineral oil based fuels
Ad 3) Please recapitulate what you’ve learnt about the
reforming process!
 Why is self-ignition less probable with branched and
cyclic hydrocarbons?
 How is the octane number defined? – Which are the two
reference compounds?
What you need:
Two porcelain pots, heptane, 2,2,4-threemethyloctane
(What’s its trivial name?), matches; Safety goggles and
protection gloves!
Fill a few millilitres of the two fuels into separate pots, put
them apart by some thirty centimetres and ignite them by
means of a match!
Now watch the two components of petrol while burning! –
What do you observe?
……………………………………………………………………………………………….
Please explain!
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Ad 4) First of all you’ll have to find out (or repeat) what
aromatic hydrocarbons are. A brief introduction may be
found at the following link:
http://library.thinkquest.org/3659/orgchem/aromatic.html
Fuels contain about 2 % of aromatic compounds. This
improves their anti-knock-qualities, but many aromatic
hydrocarbons (particularly benzene itself and certain
condensed aromatics) are carcinogenic.
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You need: different types of gasoline, toluene, aluminium
chloride (AlCl3 - corrosive!), chloroform and some test
tubes.
Please work in a fume hood with working
ventilation! Work with goggles and gloves!
First of all put a small
portion of AlCl3 into a
test tube and heat it
with the burner, so
that it sublimates and
forms a deposit on the
wall of the tube.
Now
dilute
a
few
droplets of toluene with
2-3
millilitres
of
chloroform and add a
little bit of this solution to the AlCl3 deposit by means of a
pipette. – What do you observe?
derive
constitution formula
petrol (brit.)
flammability
copious
refuel
harmful
ignite
recapitulate
fume hood
dilute
Gasoline (amer.)
abundant
noxious
repeat
Abzug, chemischer Herd
Please write down additional new words at the backside of
the pages!
Work in pairs and be aware of the necessary safety
precautions!!!
……………………………………………………………………………………………….
Explanation: Aromatic compounds form intensely coloured
adducts with Lewis acids like AlCl3.
Now repeat the whole sequence but use gasoline instead
of the toluene solution.
Observation:
……………………………………………………………………………………………...
(You can try other aromatic compounds like naphthalene
as well!)
Experiments and pictures have been taken from the website:
http://dc2.uni-bielefeld.de/dc2/auto/index.html
Work sheet: Mineral oil based fuels
E. Langer 2006
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