BRONZE MEDAL AWARD
School:
Participating Students:
∆Hcθ
St. Paul's Convent School
Koo Tien Tien Rosena
Leung Yee Ling Winnie
Ngan Yu Kuen Nancy
A New Discovery of Car Fuel
Project Title:
= -1013 kJ mol-1
With this concept, we can then carry out the combustion process to determine the
energy produced by different substances.
Combustion equation:
CXHYOZ + (x + y/4 - z/2) O2 → xCO2 + y/2 H2O
Introduction
In recent year, the government is very concerned about the type of car fuels to be
used. This brings us the idea of investigating different substances through
combustion in order to find out whether they can be used as alternative car fuels. The
substances under investigation are being divided into three groups:
a.
b.
c.
= 5E(C−H) + E(C−O) + E(O−H) + 3E(O=O) + E(C−C) - 2[2E(C=O)
+ 3E(O−H)]
common fuels: petrol, diesel oil, paraffin oil, methanol and ethanol;
different percentage of petrol-ethanol mixture;
food and fruit oil: lard, margarine, peanut oil, corn oil, canola oil, sesame oil,
olive oil, ginger oil and citral.
Experiments are being conducted to find out the amount of energy that they can
produce.
Energy produced per gram = mc∆T /mass of chemical used
where m:
mass of chemical used
c: specific heat capacity of water
∆T: temperature change of water
After calculating their energy produced in combustion, comparison can be made to
determine the most suitable alternative car fuel.
The Investigation
Part I
Principle
Procedures of combustion:
The chemical principle used in this project is based on the concept of bond enthalpy.
The following is an example:
1. Weigh an empty aluminium can and pour 250 cm3 of water into it.
2. Reweigh the can with its content and measure the initial temperature of water.
3. Fill a burner with the substance investigated. Then light the wick and adjust it to
give a flame about 1 cm high.
4. Weigh the burner with its content again and clamp the aluminium can above the
burner. Then light the burner.
5. Shield the whole set up and stir the water at frequent intervals. After the
temperature has risen for about 100 oC, record the highest temperature reached by
water. Then extinguish the flame and remove the shield.
Given the bond enthalpies of:
C−H
C=O
O−H
413 kJ mol-1
740 kJ mol-1
463 kJ mol-1
346 kJ mol-1
497 kJ mol-1
360 kJ mol-1
C−C
O=O
C−O
To calculate the enthalpy change of combustion for ethanol:
C2H5OH
+
3O2
→
2CO2 +
3H2O
∆H = energy required for bond breaking - energy required for bond forming
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Part II
A)
1.
2.
3.
B)
19.76
Part III
Procedures of preparing ethanol-petrol mixtures:
Weigh suitable amount of ethanol and petrol.
Pour the two solutions into a beaker and stir the mixture.
Fill a burner with the mixture.
Follow the same combustion procedures as in Part I
15.29
Plant oil or
Peanut oil
animal fat
Energy produced
15.59
(kJ g-1)
12.52
Corn oil
22.19
15.13
12.73
13.37
Canola oil Sesame oil Olive oil
21.93
21.53
25.32
Part III
A) Procedures of changing solid fats into molten state:
1. Cut a piece of solid fat and put it into a beaker above a Bunsen flame.
2. Stir it until it is completely melt and transfer it to a burner.
B)Extraction of orange oil:
1. Collect orange peels from six oranges and remove their outermost layer. Then cut them
into pieces.
2. Transfer them to a round-bottomed flask which contains water. Then connect the flask to a
steam generator and a water condenser to carry out steam distillation.
3. After about an hour, approximately 100 cm3 of distillate can be obtained.
C) Carry out the same combustion procedures as in Part I
Plant oil or
animal fat
Energy produced
(kJ g-1)
Lard
25.13
Margarine Orange oil Ginger oil
21.52
24.09
18.46
Citral
18.21
Discussion
From the result in Part I and Part II, we can see that petrol and the mixture of 10%
ethanol with 90% petrol give out the largest amount of energy respectively.
The set-up for steam distillation of orange oil is not provided by the participants.
However, we will not focus on these two parts. It is because they are non-renewable
resources and will be run out pretty soon. Instead, we would like to pay more
attention on the renewable source of fuels. This leads us to Part III.
Results
After conducting the experiment, we calculate the enthalpy change of combustion for the
substances. The results are as follow:
In Part III, several food oils are being investigated. From the result, we discover that
most of the oil can produce energy of about 20 - 25 kJ per gram.
Part I
Common fuel
Enthalpy change
(kJ g-1)
Diesel Oil
Petrol
Ethanol
Methanol
Paraffin oil
20.09
17.41
13.85
11.21
25.5
In order to be more effective in choosing the most suitable car fuel, we have
converted the result to 'energy produced per dollar'.
Part II
Mixtures
100% petrol
90% petrol + 80% petrol + 70% petrol + 60% petrol +
10% ethanol 20% ethanol 30% ethanol 40% ethanol
Enthalpy
change
21.43
24.87
20.84
19.89
20.65
(kJ g-1)
50% petrol + 40% petrol + 30% petrol + 20% petrol + 10% petrol + 100% ethanol
50% ethanol 60% ethanol 70% ethanol 80% ethanol 90% ethanol
From the graph, we can see that orange oil produces the largest amount of energy per
dollar, followed by the margarine and the corn oil.
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Conclusion
However, it is inconvenience to use margarine as a car fuel since it is a solid at room
temperature. As a result, we only need to compare orange oil and corn oil.
Orange oil produces more soot than corn oil when combusted. This can be explained
by their structures.
After taking careful consideration, orange oil is being chosen as the best car fuel. It
is because orange oil is a renewable resource. It produces a large amount of energy
per dollar and possesses good physical properties. It really has the potential to be
developed.
From their structures, we can see that orange oil has a higher degree of unsaturation.
The carbon to hydrogen ratio is larger and hence the pollution problem caused by
orange oil is greater than that caused by corn oil. However, we can solve this
problem by installing a special device like catalytic converter into the car.
Orange oil is a more volatile and non-viscous liquid than corn oil. These make it
easier to be ignited. Thus the engine of the car can be started more easily. Besides,
corn oil cannot be distilled at atmospheric pressure. It will choke the diesel engine of
the car during combustion.
Moreover, orange is a common fruit. Large amount of peels can be collected to make
orange oil and this reduces the pollution problem. Besides, the government can
collect peels from citizens by placing some 'orange peels collection box' on the street.
With large amount of peels available, the price of orange oil will then be lowered.
St. Paul's Convent School