=1.90mL
Volume of popcorn in litres
= (Volume of popcorn in ml) / 1000
= (1.9 ml ± 0.01 ml) / 1000
= 0.0019 L
Mass of Water Lost
Mass of flask, oil, and unpopped popcorn- Mass of flask oil and popped popcorn
105.74g - 105.43g
= 0.310g
Moles of water lost
moles = Mass of water
Molar mass of water
n= 0.31g
18.01g/mol
=0.0172 mol
Percent water in kernel
Mass of water lost x 100
Mass of 16 kernels
0.31g/2.34g x 100%
= 13.25%
Pressure of steam inside kernel at time of pop
PV= nRT
P=nRT
V
= (0.0172) (0.0821L x atm x mol-1 x K-1) ( 273+225)
0.0019
= (0.0172) (0.0821L x atm x mol-1 x K-1) ( 498)
0.0019
= 365.82 atm
Error Propagation of Multiplication and Division
ΔZ = √[(Δx/x)2 + (Δy/y)2] x Z
Δz = error propagation
Δx = uncertainty of value 1
x = Value 1
Δy = uncertainty of value 2
y =Value 2
z = Final Value
Pressure of Steam inside kernel at time of pop
= √[(0.003/0.6950586)2 + (0.0001 /0.0019)2] x 365.82
= √[0.00001862943428 + 0.0052631579] x 365.82
= √[0.0052817873] x 365.82
= 0.0726759061 x 365.82
= 27.58629997
≈ 27.60 atm
Data Processing
Table 5. Mass of corn before and after heating
Table 6. Volume of popcorn, mass and moles of water lost, percentage of water in kernels, and pressure of steam inside kernel at time of pop
Conclusion and Evaluation
Conclusion
Popping popcorn requires the heating the corn until the pressure inside the kernel is greater than the pressure outside to cause the outer layer of the corn to burst and turning it inside out and release the moisture inside. The percentage of the water lost was calculated to 13.2% ± 0.4% . The pressure inside the kernel at the time of pop was calculated using the ideal gas law which states that when particles that occupy the same volume under a constant temperature, any changes in volume is inversely proportional to pressure changes . This law was used because the particles were small relative to the distances between them, there were no intermolecular forces of attraction and a constant temperature was assumed. Using ideal gas law equation, the pressure was calculated to be 365.82 atm ± 27.60atm.
Limitations
The errors of the experiment include parallax when reading the values of water on the graduated cylinder which could cause the calculation of the volume of the kernels to go either up or down. The kernels might not be completely dried off after the displacement which could cause the mass of the corn and the water lost to increase. In addition, there could have been moisture still left in the flask after cleaning it which can cause the mass of water lost to increase. Also, errors include burning the popcorn which can also affect the mass of water lost by increasing that value and not popping all of the corns could bring the value of water lost down since the moisture is still trapped inside. The sizes of the kernels were not the same and therefore the pressure required for it to pop vary which will alter the results of the pressure since it is not uniform. After the experiment, there could have still been water condensation left in the beaker that would increase the mass of the popped corn and decrease the mass of water lost. Lastly, the temperature was assumed to be 225oC at the time of pop which is probably not highly accurate. This would make the calculation of the pressure inaccurate since it depends the value of the temperature.
Improvements
Improvements that could be made to this experiment include allowing more time for the corn to dry after displacing the kernels so there would not be excess moisture to alter the mass of water lost. The use of a curved sponge to clean and dry the inside of a Erlenmeyer flask would eliminate the chance of moisture remaining inside that could causes the mass of water lost to increases. Also, choosing kernels of similar sizes would improve the chance of the corn having uniform pressure inside the kernel at the time of pop and in turn improve the accuracy of the calculation of the pressure inside the kernel. More trials of this experiment could have been done to improve the accuracy of the results. Perhaps, calculating the atmospheric pressure and comparing that with the pressure inside the corn would help with a greater understand of the amount of pressure inside the corn if there was a comparison.
WORKS CITED
"Ideal Gas Laws." Aus-e-Tute. 8 Apr. 2009 <http://www.ausetute.com.au/idealgas.html>.
"Ideal Gas Laws." Aus-e-Tute. 8 Apr. 2009 <http://www.ausetute.com.au/idealgas.html>.