Source D- Page 1
CU3.2: Energy from fuels
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Date accessed: 28 May 2012
Project - Heat of Combustion (P1)
will use the following equation:
Introduction
Where
m = mass of water (g)
s = specific heat of the water (4.2 J / g C)
t = rise in temperature of the water
Q = the amount of heat energy that is generated by x grams of the fuel
It is often observed that chemical reactions result in a change in heat energy.
Depending on the reactions, this heat energy is either absorbed or produced.
Any reaction that absorbs heat is called endothermic, and any reaction that
produces heat is called an exothermic reaction. It has been determined that if a
reaction takes place within a closed, insulated container, then the heat absorbed or
produced by the reaction will cause a distinct temperature change in the contents of
the insulated container. This difference in heat energy of the reactants can be
calculated and provides a quantitative measurement of the heat produced (or
absorbed) in the chemical reaction. This experimental technique, the science of
measuring heat, is called calorimetry. Any experiment in which heat is produced or
absorbed and interacts with the environment (for example, the container) can be
studied with calorimetry.
The calorific value of the fuel is the total amount of energy produced when 1 unit of
mass of fuel undergoes complete combustion. For example, if 1 gram of fuel X is
burnt and produces 50 kilojoules of energy, the calorific value of fuel X is therefore
50 kJ/g. The calorific value of fuels can be compared to determine which one is most
efficient and can generate the greatest amount of energy. Also, properties of fuels
can be compared and predicted based on their calorific values. In the experiment,
the calorific values of the three fuels will be determined and can then be compared
to show which of the three fuels has the greatest heat-generating capacity.
The experimental technique of calorimetry requires the use of a calorimeter, an
instrument used to measure the heat of the reaction and thereby, any temperature
changes during the course of the reaction. There are a variety of calorimeters,
ranging from very large, sophisticated ones to simple designs that can be used in a
school lab. The calorimeter must be a well-insulated container that can prevent any
exchange of heat with the environment. Based on these specifications, even a
Styrofoam cup can be successfully used in a school lab in place of a more
expensive calorimeter. For this experiment we will use an aluminum calorimeter.
To calculate the calorific value of a fuel from the data given by the calorimeter, we
Q=m×s×t
The purpose of the experiment is to ascertain how the efficiency of a fuel can be
measured and compared against other fuels using solely the experimental technique
of calorimetry in determining the calorific value of that fuel.
Materials
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Paraffin Wax
Cooking Oil
Butane
50 g of Water
Graduated Cylinder
Calorimeter
Thermometer
Scale
Safety Goggles
Diagram of Calorimeter
Source D- Page 2
CU3.2: Energy from fuels
Website: http://vinstan.wikispaces.com/Project+-+Heat+of+Combustion+(P1 and http://vinstan.wikispaces.com/file/view/Heat+of+Combustion+P1.pptx
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
50 g of water was poured into the calorimeter.
The temperature of the water was measured and recorded.
Paraffin wax was obtained, measured, and placed into the calorimeter.
The paraffin wax was ignited and allowed to burn for at least 2 minutes, or
until the flame went out.
The temperature of the water was measured again and recorded.
The paraffin wax was disposed of and the calorimeter's compartments were
cleaned thoroughly.
The water was disposed of and replaced.
Steps 2 through 7 were repeated for cooking oil and butane.
The work area was cleaned and all equipment replaced.
Date accessed: 28 May 2012
Observations
The following observations were made during the experiment:
Data Table
Fuel
Initial
Temperature
of water (°C)
Final
Temperature
of water (°C)
Paraffin
22.5
Wax
Cooking
22.5
Oil
Butane
22
*Includes container
25.6
Initial
Mass of
Fuel*
(g)
16.963
Final
Mass of
Fuel*
(g)
16.877
25
9.575
39
210.443
ΔMass(g)
0.086
134
9.534
0.041
40
210.170
0.273
120
Calculating Difference in Temperature (Δt)
= (final temperature) – (initial temperature)
Paraffin Wax: = 25.6°C – 22.5°C
Cooking Oil:
= 25°C – 22.5°C
Butane:
= 39°C – 22°C
= 3.1°C
= 2.5°C
= 17.0°C
Safety
Safety goggles and appropriate protective clothing were worn, and all long hair was
tied back. The experiment area was cleared of all unneeded equipment and
flammable material. When the experiment was performed, an adult was present. Fire
exits and procedures were known to all participants. Butane was handled with
particular care, as it is very flammable as well as poisonous if inhaled. After the
experiment was performed, the experiment area was cleared and all refuse was
disposed of accordingly.
ΔTime
(s)
Calculating Heat Produced (Q)
= (mass of water used) x (specific heat capacity of water) x (difference in
temperature)
Source D- Page 3
CU3.2: Energy from fuels
Website: http://vinstan.wikispaces.com/Project+-+Heat+of+Combustion+(P1 and http://vinstan.wikispaces.com/file/view/Heat+of+Combustion+P1.pptx
Date accessed: 28 May 2012
fuels and compare their efficiency to current fuels.
Paraffin Wax:
Cooking Oil:
Butane:
= 50 x 4.18 x 3.1
= 50 x 4.18 x 2.5
= 50 x 4.18 x 17
= 647.9 J
= 522.5 J
= 3553 J
Calculating Calorific Value
= (heat produced) / (mass of fuel burned)
Paraffin Wax:
Cooking Oil:
Butane:
= 7.53 kJ/
= 12.74 kJ/g
= 13.01 kJ/g
Conclusion
This experiment was done to try to determine the calorific value of 3 different fuels
by using the techniques of calorimetry. The fuels were burned inside a calorimeter,
and the resulting changes in the mass of the fuels and the temperature in the
calorimeter were used to calculate the calorific values of the fuels. It was concluded
that calorimetry techniques can be used to measure and compare the combustion
efficiency of a fuel against other fuels. Out of the 3 fuels that were tested in the
experiment, butane released the most heat during combustion and therefore, is the
most effective fuel.
Discussion
There are many ways to apply the technique of calorimetry in the real world. Oil
companies, for example, are always looking for better gasolines, and so the
techniques of calorimetry can be used to compare and measure the efficiency of
fuels and to help find better and more efficient fuels. By using the technique of
calorimetry to experiment on different types of gasoline, one can test potential new
The technique of calorimetry is also used to help people understand their diet and
their energy intake. The number of calories of a certain food can be found on most
nutrition labels. These numbers were most likely found using a calorimeter, since
calorimetry and the process of respiration and energy consumption in the human
body are quite alike. Once food is consumed by a person, the food is "burnt" inside
the person's body through the process of respiration. This process results in the
release of energy. This is quite similar to the combustion of a fuel with oxygen so the
number of calories is really just the calorific value of the food per serving size.