MEEN 3242 MEE LAB II
Experiment Report
Lab # 2 – Bomb Calorimeter
Group Members:
Hugo Diaz
Reed Greenwood
Juan Orona
Alan Sanoja
Micheal Shackelford
Date: September 27, 2013
DEPARTMENT OF MECHANICAL AND ENERGY ENGINEERING
UNIVERSITY OF NORTH TEXAS
2013 FALL
Lab #2 – Bomb Calorimeter
CONTENTS
1. Introduction ............................................................................................................................................................... 2
2. Background and theory ............................................................................................................................................. 3
3. Procedure .................................................................................................................................................................. 5
4. Results and Conclusion ............................................................................................................................................ 10
5. Uncertainty Analysis ................................................................................................................................................ 13
6. Conclusion ............................................................................................................................................................... 14
7. References ............................................................................................................................................................... 15
8. Team Members photo ............................................................................................................................................. 16
9. Data Sheet (Scanned copy) ...................................................................................................................................... 17
1. INTRODUCTION
Abstract
In this experiment we measured the energy density for flammin’ hot cheetos using a bomb
calorimeter. We burn benzoic acid to find out the heat capacity of the equipment and we then
burned a small amount of the flammin’ cheetos. We got [value] for the energy density of the cheetos,
and the value on the nutrition label is [value]. We can see that our values are [compare] to the value
on the label.
Introduction
In this experiment we will be using a bomb calorimeter. A bomb calorimeter measures the heat
combustion during a reaction. This will allow us to measure the amount of calories contained in hot
Cheetos and be able to compare the results to the value on the nutrition label. We will first find out
the heat capacity of the calorimeter using benzoic acid, since it fully combusts in oxygen. The bomb
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Lab #2 – Bomb Calorimeter
calorimeter is a closed system, therefore there is no heat transfer with the surroundings and we will
be able to use the First Law of Thermodynamics, conservation of energy, to find out the necessary
values. (Traum, 2009)
2. BACKGROUND AND THEORY
Bomb calorimetry is a process which can be used to determine the heat of combustion or calorific
value of a solid or a liquid material. The Bomb Calorimeter was invented by a great chemist in the
18th century named Marcellin Berthelot. A simple liquid or food is compressed with oxygen inside a
sample container or sample cup within the bomb calorimeter. The bomb calorimeter is ignited
producing heat to the samples, which is then measured by the change in temperature of the
surrounding water. In figure 1 we can see that the system is a closed system there is no heat
exchange between the surrounds or calorimeter making it an adiabatic system.
Figure 1. Bomb Calorimeter( McMurray Fay, Chemistry Fourth
Edition)
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Lab #2 – Bomb Calorimeter
Applying first law of thermodynamics allows the use of the following equations.
Since there work is no being done or heat being absorbed by the system, the total energy change is
zero allowing the following question to be valid.
Once the sample is burnt, heat released is then absorbed through the water which provides a set of
different temperature readings that is provided by the Bomb Calorimeter. There are a couple
procedures that must be followed in order to obtain the proper results. It is important to evaluate the
unknown heat capacity of the bomb calorimeter using Benzoic Acid, a known substance that combusts
completely in oxygen. There a couple of equations that can be used throughout the procedure.
By using the specific heat capacity of water which is 4.2 KJ/KgK and the given nutrition facts of the
sample, we can determine if the results discovered are equal or match what is given on the nutrition
label.
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Lab #2 – Bomb Calorimeter
3. PROCEDURE
.
[Oxygen distribution system]
Experimental Equipment
[IKA C2000 Calorimeter]
5
[Mettler Toledo]
Lab #2 – Bomb Calorimeter
6
Lab #2 – Bomb Calorimeter
[Multi-meter & type K thermocouple]
[Pitcher]
Procedures
1. Empty the calorimeter containment vessel and combustion crucible. Put together the
containment vessel (or “bomb”) using an empty combustion crucible.
2. Initiate power to the IKA C200 bomb calorimeter.
3. Determine the mass of water used by the calorimeter, thread on the white plastic ignition
cap to
the containment vessel. Put the sealed, empty containment vessel that has
been sealed and capped into the calorimeter cavity. Close the lid securely.
4. Pour the water in the pitcher into the calorimeter reservoir tank. The liquid level should be
between the high and low marks on the reservoir tank. Please fill reservoir to above
the minimum level.
5. Weigh the pitcher on the Mettler-Toledo high-capacity balance then write down its weight
and the uncertainty associated with this measurement.
6. In the calorimeter action screen, Press “Prepare” and use the default values only. Press
“O.K” (F1)
7. Once the “Storage Filled” prompt appears, Press “continue” (F1) to fill the calorimeter fluid
jacket.
8. Put the collection pitcher under the calorimeter drainage tube to catch the expelled water.
9. After the calorimeter fluid jacket is full, the calorimeter will start “Equalizing”. When this
happens abort the experiment by opening the calorimeter lid. This will causes the
calorimeter to drain into the graduated fluid collection pitcher. This may take several
minutes
10. Place the now full graduated fluid collection pitcher upon the Mettler-Toledo highcapacity balance and record its weight and the associated uncertainty. The difference
between the full and empty pitcher weight is the mass of water used by the
calorimeter.
11. Repeat Steps 3 –10 11 times. Use the average of the 11 resulting mass measurements of
the water used by the calorimeter. Substitute the standard deviation for the
uncertainty of the mas of the water. Don’t use the first measurement if this data point
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Lab #2 – Bomb Calorimeter
is way off from the previous measurements.
12. Put the empty crucible on the Mettler-Toledo high-precision balance. Zero or tare the
scale (calibrate), then put ONE tablet of benzoic acid in the combustion crucible and
weigh again to get the mass of the benzoic acid tablet. This is needed for later
calculations. The energy density of the acid is given as 26460 J/g. Please note this Acid
is an eye and skin irritant. Use gloves provided when handling this substance.
13. Un screw the calorimeter containment vessel lid and mount the benzoic acid -filled
crucible inside.
14. Thread one piece of cotton over the containment vessel as an ignition wire. Be sure to
assure the twine is contacting with the acid tablet.
15. Screw the lid back on to the combustion chamber, sealing it hand tight.
16. Connect the sealed, assembled, loaded containment vessel to the oxygen gas filling
station
17. Open the oxygen gas tank to release the gas.
18. Dial in the gas tank regulator to 30 bar. The check valve on the gas tank regulator may
open with an audible hiss. Quickly disengage the combustion chamber from the fill
assembly. DO NOT overfill the chamber. If the chamber is accidentally overfilled bleed
it off with the pressure relief tool and repeat Steps 16 – 18.
19. Put the gas charged containment vessel onto the calorimeter cavity. Insert the
thermocouple into the calorimeter cavity. Close the lid.
20. At the calorimeter action screen Press “Prepare” (F2) and accept all the default values,
press “O.K” (F1).
21. Put the water in the pitcher into reservoir tank.
22. Put the pitcher under the calorimeter drainage tube to catch the discharge water.
23. When the “Storage Filled” prompt appears, Press “continue” (F1) to fill the calorimeter fluid jacket.
24. After the calorimeter fluid jacket is full, read the thermocouple reader for water
temperature. Record this value.
25. Each minute after, record water temperature from the thermocouple reader for about 10
minutes (collect 10 data points, you need this to calculate the mean and standard
deviation of the initial temperatures) in order to ensure the temperature of the
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Lab #2 – Bomb Calorimeter
calorimeter becomes stable. The average will be the initial temperatures of the water.
26. Once 10 data points have been collected, press the “Ignition” (F1) button.
27. If ignition is successful, you will see the water temperature starts increase. If not, ask the
T / A for help. Possible reasons could be the cotton wick is not touching the food
sample adequately, or the Bomb is not placed on the right position.
28. Record water temperature from the thermocouple reader for another 15 minutes (once a
minute) to ensure the temperature inside the calorimeter be come’s stable. When the
temperature starts decrease, collect another five data points.
29. Remove the Bomb, and towel dry it, and use the pressure relief valve to relieve pressure.
30. Remove the crucible from the chamber. Note whether it contains residue or ash. Weigh
the crucible and any remaining ash on the Mettler-Toledo high precision balance. Record this value while noting the difference is the actual amount of Benzoic acid that
burnt.
31. Repeat steps 12 - 30, but this time uses your food sample Do not use food sample with a
mass over 2 grams. Note the caloric value of the food sample from the nutrition facts
label. This information is needed for later comparison.
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Lab #2 – Bomb Calorimeter
4. RESULTS AND CONCLUSION
Water(g)
Pitcher
Run 1
2108
186
Run 2
Run 3
2089
2098
186
186
Run 4
Run 5
2085
2104
186
185
Run 6
Run 7
2085
2103
186
186
Run 8
Run 9
2101
2092
186
186
2106
2097.1
186
185.9
Run 10
Average
Standard
Deviation
Water
Benzonic Acid Burn
1.0166 grams
ignited
8.698020209 0.316228
1911.2 ml
Temp
(C°)
Time (s)
21.8
60
21.9
21.8
120
180
21.8
21.8
240
300
21.8
21.8
360
420
21.9
22.5
480
540
22.8
23
600
660
23.1
720
23.2
780
23.2
840
∆T (C°)
1.4
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Lab #2 – Bomb Calorimeter
Flamin Hot Cheetos
.6829 grams
ignited
∆T (C°)
Temp
(C°)
Time (s)
22.5
60
22.6
22.5
120
180
22.5
22.6
240
300
22.6
23
360
420
23.2
23.4
480
540
23.4
23.5
600
660
23.6
720
23.6
780
23.6
840
1.1
−𝑞𝑠𝑎𝑚𝑝𝑙𝑒 = 𝑞𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 +𝑤𝑎𝑡𝑒𝑟
𝐽
−𝑞𝑠𝑎𝑚𝑝𝑙𝑒 = − (26460 ) (1.0166 (𝑔)) = −26899.236 𝐽
𝑔
𝑞𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 = (𝑀𝑤𝑎𝑡𝑒𝑟 𝐶 + 𝑀𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝐶)∆𝑇
𝑀𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝐶 =
𝐻𝑒𝑎𝑡 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = 𝑀𝐶𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝐶 =
[𝑞𝑠𝑎𝑚𝑝𝑙𝑒 − 𝑀𝑤𝑎𝑡𝑒𝑟 ∗ 𝐶 ∗ ∆𝑇]
∆𝑇
[26899.236 − (1911.2 ∗ 4.2 ∗ 1.4)]
= 11186.7 𝐽/𝐶
1.4
−𝑞𝑠𝑎𝑚𝑝𝑙𝑒 = 𝑞𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟
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Lab #2 – Bomb Calorimeter
𝑞𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 = ℎ𝑒𝑎𝑡 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 ∗ ∆𝑇
𝑞𝑐𝑎𝑙𝑜𝑟𝑖𝑚𝑒𝑡𝑒𝑟 = (11.1867
(12.305327 𝑘𝐽) (
𝑘𝐽
𝐾
) (1.1𝐾) = 12.305327 𝑘𝐽
𝑘𝑐𝑎𝑙
) = 2.92985 𝐶𝑎𝑙𝑜𝑟𝑖𝑒𝑠
4.2𝑘𝐽
(Experimental Data)
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Lab #2 – Bomb Calorimeter
Sample Size = .6829 grams
28𝑔 = 160 𝑐𝑎𝑙𝑜𝑟𝑖𝑒𝑠
5.7142857 𝑐𝑎𝑙𝑜𝑟𝑖𝑒𝑠/𝑔𝑟𝑎𝑚
(. 6829 𝑔𝑟𝑎𝑚𝑠) (5.7142857
𝑐𝑎𝑙𝑜𝑟𝑖𝑒𝑠
) = 3.9022
𝑔𝑟𝑎𝑚
(According to Manufacturer)
5. UNCERTAINTY ANALYSIS
Uncertainty Analysis:
𝑄̇
1
2𝜋𝑅𝑔2
= √(1/2(ℎ22 ∗ ℎ1 + ℎ21 ∗ ℎ2 ))
The right hand side uncertainty evaluation is as follows:
𝑅𝐻𝑆 % 𝑒𝑟𝑟𝑜𝑟 = √3 (
∆ℎ1 2
∆ℎ2
) + 3(
) = 1.05813 ∗ 100% = 105.813 %
ℎ1
ℎ2
The left hand side uncertainty evaluation is as follows:
𝐿𝐻𝑆 % 𝑒𝑟𝑟𝑜𝑟 = √(
∆𝑄̇ 2
∆𝑅
) + ( )2 = .049076 ∗ 100% = 4.9076 %
̇
𝑅
𝑄
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Lab #2 – Bomb Calorimeter
So the tolerances felt on the measurements are as follows:
√1/2(ℎ22 ∗ ℎ1 + ℎ21 ∗ ℎ2 ) = 4.09755 ± 1.06
𝑄̇
1
2𝜋𝑅𝑔2
=
51340.736
32391.8
= 1.64056 ± .05
6. CONCLUSION
Although the data gives a reasonable number for the calories, it is not a perfect number. This
is due to error that could have happened from the scale not being right, the food sample not burning
completely, or the reading for the water temperature not being correct due to it being on the side of
the container instead of in the middle of the water.
(12.305327 𝑘𝐽) (
𝑘𝑐𝑎𝑙
) = 2.92985 𝐶𝑎𝑙𝑜𝑟𝑖𝑒𝑠
4.2𝑘𝐽
(Experimental Data)
(. 6829 𝑔𝑟𝑎𝑚𝑠) (5.7142857
𝑐𝑎𝑙𝑜𝑟𝑖𝑒𝑠
) = 3.9022
𝑔𝑟𝑎𝑚
(According to Manufacturer)
Had we burned a larger sample we would have gotten a number closer to the manufacturer number.
The small sample size allows other factors to be more influential to the final product. We were about
30% off the mark but had we run the experiment a few more time we would reduce the experimental
errors along with human errors.
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Lab #2 – Bomb Calorimeter
7. REFERENCES
"Marcellin Berthelot." HowStuffWorks. Web. 25 Sept. 2013.
Web<http://science.howstuffworks.com/dictionary/famous-scientists/chemists/marcellin-berthelotinfo.htm>
Traum, D. M. (2009). Bomb Calorimetry.
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Lab #2 – Bomb Calorimeter
8. TEAM MEMBERS PHOTO
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Lab #2 – Bomb Calorimeter
9. DATA SHEET (SCANNED COPY)
17