I enjoy studying Organic chemistry and I feel it is
the most interesting part of chemistry. While learning this topic in IGCSE, we
performed experiments involving organic compounds and analysed their
properties. I used this knowledge to research about real life applications of
alcohols and found thousands of uses of alcohols in various sectors including;
pharmaceuticals, medicals, perfume production, alcohol production and fuel
industries. Although, from all of these I was more interested in how fuel were
made from alcohols as they can be good alternatives to fossil fuels since they
do not produce harmful gases upon combustion. I love exploring organic
compounds as they are used everywhere for everything. The most interesting part
of them is that they have different odours so it is easy to recognise them.
This is essential during gas leaks.
Therefore, I wanted to investigate how alcohol
combustion produces energy, which can be used as a fuel. In addition, I wanted
to find out which alcohol will give me the best results hence this experiment
question: To investigate combustion of which alcohol gives out
most energy to heat
water from room temperature to 50°C, when their
volume has been controlled?
We all know alcohols as intoxicating drinks, but not
all alcohols are consumed as drinks. Alcohols are organic hydrocarbon compounds
of the homologous series with –OH functional group. They are highly flammable
therefore are also used as fuels. (Bite size, 2014)
All alcohols undergo similar reactions as all of them have similar chemical
properties. The first four alcohols in the homologous series are methanol,
ethanol, propanol and butanol. Each of these alcohols has one additional
hydrocarbon bond than the one before. Therefore the compound’s flammability
increases with increasing hydrocarbon bond.
The first four alcohols are used as fuels because
they are easily synthesised chemically or biologically and they have characteristics,
which allow them to be used in internal combustion engines. As these are
organic compounds, they only produce water and carbon dioxide when they are combusted,
which does not harm the environment directly. The carbon dioxide produced is
reduced from the environment by biomass plants, which are used to produce
alcohols. One example of this is ethanol production by planting sugar canes and
fermenting them to make ethanol. Therefore, these plants use the CO2 that is
produced by combustion of ethanol therefore does not affect the environment. (n.p., 2018.)
Overall reaction that occurs: Alcohol + oxygen ? carbon dioxide + water
Hence, for this reason, alcohols are also considered
as renewable resources and as they are more reasonable in price compared to
other alternative resources, they have more chances to be developed and used in
the future. In addition, many of their physical-chemical properties are
compatible with the requirements of modern engines, which make them attractive
either as replacements for fossil fuels or as fuel additives.
Alcohols (100 cm³each)- Methanol, Ethanol, Propa-1-ol, butanol
100cm³ of water
(conical flasks (2x250cm³), measuring cylinder
(2x10cm³) and beakers (2x100cm³)) -(±0.05
any other) weighing scale
all the apparatus and materials needed for this experiment, on the lab table.
Then, measure the mass of empty spirit burner and conical flask using an
electronic (or any other) weighing scale and note it down.
Next, measure 50.0cm³ of methanol and pour it in the spirit burner using
a 10.0cm³ measuring cylinder for precision. Similarly,
measure 100.0cm³ of water and pour it in the conical flask. Note
down their initial temperature, mass of alcohol with the spirit burner and mass
of water with the flask.
Now, we setup
the apparatus as shown in the diagram below.
Light the wick
of burner and simultaneously start timing the experiment, stop the stopwatch
when the water temperature reaches 50.0°C from its initial temperature and note the results
off the flame and remove the conical flask from the clamp stand, and measure
its mass before disposing the water. Also, measure the mass of alcohol. Note
these results down.
procedure, from step 2, for the other three alcohols. Note there results down.
For more accuracy, repeat the whole experiment at least four times.
the average time taken to heat water to 50.0°C for all the alcohols and compare their results.
Considering all the limitations and with the
reference to the background information it can be assumed that during this
experiment, Butanol will give out the most energy upon combustion due to the
fact that it has the most number of hydrocarbon bonds.
were worn throughout the experiment- for eye protection.
I conducted the
experiment in a well-ventilated room as my experiment involved combustion,
which will produce a harmful gas like carbon monoxide if sufficient oxygen
level is not present.
I wore gloves
when pouring the alcohols and lab coat throughout the experiment for safety
I diluted the
chemicals before disposing them in the sink.
I conducted the
experiment in a room with sufficient oxygen level so that the alcohol does not
produce harmful gas like carbon monoxide.
I let the water
cool before disposing it in the sink as hot water can harm aquatic and
Dependent variable- the dependent variable in this
experiment is time taken for water to reach 50°C and final mass of alcohol after the
variable- the independent variable in this experiment is the alcohols.
How I controlled it
Importance of it
Amount of alcohol used
I used 50cm³of
each for all experiments.
So that the results are accurate,
I can compare my results.
Amount of water
I used 100cm³for
Therefore, it does not affect
the results hence can be fairly compared.
Types of apparatus
Same apparatus are used for all
So that there is no
manipulation and errors in result.
Spirit Burner with alcohol
Conical flask with Water
I performed four trials for each alcohol combustion
experiment- for more accurate results and averaged the time for each alcohol to
heat water to 50°C. By doing this, I could also see the anonymous
results of the experiment.
carried out four trials for this experiment also and averaged the final mass
for each alcohol.
Bright yellow than faint blue
Faint Yellow then blue
Although, physical change like change in colour or
shape is not seen in this experiment, it does have chemical changes that are
not possible to be witnessed with naked eyes. These changes include the
reaction between alcohol and oxygen-which was exothermic and the heat transfer
But there were some changes that were visible like;
the temperature change-temperature rise from room temperature to 50°C was seen on the thermometer, change in mass-as
initial and final mass of the alcohols were recorded and the time difference
was also seen through the experiment.
above table shows the flame colour for each alcohol spirit burner; however,
this does not justify anything, as it is only a result of how it reacts with oxygen,
which gives it a specific colour.
Average time taken to heat water to
50°C (± s)
As shown in the graph, butanol takes the least time
to heat water to 50°C therefore can be
stated that it gives out most energy in less time.
The time and mass (below) was found
by using the following formula to get the time and mass difference for the reaction-taking
value –Initial value
Average final mass of alcohol (±cm³)
This graph shows the change in final mass after the
experiment and that it increases with increasing hydrocarbon bond. A very less
amount of butanol produces a lot of energy.
The overall chemical reactions taking place in this
combustion experiment are:
oxygen ? carbon dioxide + water
+ 3O2(g) ? 2CO2(g) + 4H2O(l)
oxygen ? carbon dioxide + water
+ 6O2(g) ? 4CO2(g) + 6H2O(l)
oxygen ? carbon dioxide + water
+ 9O2(g) ? 6CO2(g) + 8H2O(l)
+ oxygen ? carbon dioxide + water
+ 12O2(g) ? 8CO2(g) + 10H2O(l)
I used the following formulas to
find out how much energy was released after the combustion:
Specific Energy= Energy released from fuel / Mass of fuel
E= (100) x 79.5 J/ (mol K) x (50-28) = 174,900 J
S.E= 174,900 / 50 = 3498 J
E= 100 x 112.4 J/ (mol K) x (50-28) = 246,400 J
S.E= 246,400 / 50 = 4928 J
E= 100 x 143.96 J K?1 mol?1 x (50-28) =
S.E= 316,712 / 50 = 6334.24 J
100 x 179.5 J K?1 mol?1
x (50-28) = 394,900 J
S.E= 394,900 / 50 = 7898 J (Specific heat capacity of butanol for temperature
difference between 28-40°C., (2017).
After analysing data, it can be justified that
Butanol gives out the most energy after combustion and heats up water from room
temperature (28°C) to 50°C the quickest. In
addition, we see the general trend of increasing every one-hydrocarbon bond
increases its flammability that can be shown by this simple equation:
(n) Number of hydrocarbon bond ? flammability of
above equation, Butanol has the highest number of hydrocarbon bonds from all
the alcohols used in this experiment and therefore this organic compound reacts
more readily with the oxygen in the air to produce more energy than the other
Butanol is normally
used as fuel in gaseous form in portable stoves. They are much lighter and
cheaper than the other gaseous fuels. In addition, they are economically,
ethically and environmentally far more beneficial than leaded fuels and crude
oil. Economically because they are cheap, they are ethical as they do not harm
people and society and are safe to use and produce and benefit environment, as
they do not produce harmful gases like SO2 and NO2.
Limitations and Errors:
different errors and other limitations of this experiment:
it affected the experiment
can it be reduced
wick burned on its own hence it is not easy to keep the thickness of the wick
different wicks and measuring their thickness will help attain precise
might have fluctuated due to the wind.
protection board or fume board should be used to prevent the wind affecting
affected the experiment
How can it be
related to measuring the calibrated cylinder, conical flask and the
cause the change in amount of water and alcohol measured and temperature of
them, thus affect the results.
measurements should be obtained by reading the lower meniscus.
Timing the experiment
cause the initial rate to differ. Only the final time for the temperature to
reach 50°C was taken.
should be repeated several more times for better accuracy in results and
readings should be taken.
for the alcohols were not the same.
cause the results to be unreliable.
should be started at same time for all solution.
affected the experiment
How can it be
The wick of
the spirit burner was not changed during the experiment
after some time the wick size will reduce and not reach the alcohol, which
will reduce the energy production rate.
should be used for every experiment so the results are fair.
will spill which might have affect its initial mass.
should be used to add alcohol
burner was used for all experiments
Some amount of
alcohols will be mixed with the other hence affecting the results.
burner should be washed thoroughly before reusing for the next experiment or
an alternative spirit burner should be used-although these should also be
washed before using.
Evaluation and further expansion of
The experiment was conducted without a fume board or
protection board therefore could have become harmful. Thus, next time full
protection must be used to avoid risks. In addition, only one reading of time
was taken hence the anonymity within the data/experiment could not be deducted
and this could have affected the results. Considering all of these points, the
experiment can be done better next time.
Secondly, this experiment can be taken forward to a
bigger stage by using other alcohols to produce more energy than butanol. Thus,
this ideology can be used by governments to build bio fuel plants and start
using them in place of fossil fuels as this will reduce environmental pollution
and provide more energy. It is not only a good alternative renewable source but
also economically beneficial. Bio fuels do not only reduce carbon dioxide from
air but their plants (the trees used for bio fuel production) also return
oxygen to the atmosphere.
The methodology of this experiment was simple and
the results were plotted on a simple bar graph as only one-time readings were
taken. However, the method was reliable as I was able to determine the alcohol,
which gives out the most energy during its combustion-reaction with oxygen. In
addition, I required the least time taken by an alcohol to heat water to 50°C to know which alcohol gives out the most energy
upon combustion, which I was able to perceive successfully, from this