Percentage of Water In Popcorn

The purpose of this lab was to find the percentage of water in each sample of popcorn in order to determine which brand of kernels: beta, gamma, or delta, all with different amounts of water, produced the best-popping popcorn. The amount of water in the popcorn affects the quality of the popcorn. When the water inside the kernel is heated above 100�C, the water turns into gas which causes the pressure inside the kernel to increase. The pressure of the gas expands the kernel, which causes it to pop.

Quality was judged on the basis of the rate of the pops, the size of the popcorn, and how easily the popcorn burned.

Each technique of popcorn was divided up into three piles in order to conduct three trials on each technique. A group of kernels was massed and then placed into a beaker, which was also massed. Then just enough oil was poured into the beaker to cover the bottom of the beaker with a thin film of oil.

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A piece of foil with tiny holes was placed over the beaker, and the beaker with the foil, oil, and kernels was massed.

The kernels in the beaker were heated using a Bunsen burner. (See Figure 1 - Setup Diagram) While the kernels popped, the beaker was shaken in order to prevent the popped popcorn from burning and to shake the unpopped kernels to the bottom. Once all the kernels had popped, the beaker was removed from the Bunsen burner and set to cool.

After it had cooled, the beaker with foil, oil, and kernels were massed again. The same steps were repeated for the rest of the samples and qualitative observations were made throughout the experiment.

Multiple trials were used in this experiment to increase the chances of accuracy and to determine which data is reliable. If there were not multiple trials, then there is no way of knowing whether the data collected by one trial is accurate or completely inaccurate.

To find the amount of water in each kernel, this formula was used:

mass of unpopped popcorn - mass of popped popcorn �100 = % of water in unpopped popcorn

mass of unpopped popcorn

The mass of the unpopped popcorn in the numerator was the mass of the kernels before they were popped added to the beaker, foil, and oil. The mass of the popped popcorn was the mass of the popped kernels added to the beaker, foil, and oil. The mass of unpopped popcorn in the denominator was the actual mass of the unpopped kernels massed alone. The beta kernels hold 11.1%, 11.3%, and 10.9% water for trials 1, 2, and 3 respectively. The gamma kernels are composed of 16.7%, 15.7%, and 14.8% water, while the delta kernels contain 19.4%, 17.0%, 19.0% water for trials 1, 2, and 3 respectively. (Refer to appendix for original data and calculations).

See Table 1 - Percentage of Water in Popcorn Beta, Gamma, and Delta

The data for beta was the most precise among the three different techniques. The data for delta fluctuated the most and was the least precise. According to my data, the delta kernels had the highest percentage of water and the beta kernels had the lowest percentage of water. The gamma brand was in between the two. In my qualitative observations, I observed that the gamma kernels popped the fastest, smoothly, and produced the largest popcorn. I observed that the delta kernels produced the medium-sized popcorn, and the beta kernels tended to burn very easily and produced the smallest popcorn. Basically, the beta brand of kernels was the worst popping popcorn, while the gamma brand of kernels produced the best popping popcorn. These results convey that too little water within kernels make bad popcorn, and too much water produces just medium-sized popcorn. From the overall calculations and averages, it can be concluded that 15-16% water in a kernel produces the best popcorn.

To find the theoretical amount of water in the popcorn, the most accurate data of the class were added together and averaged. When compared to the class average, the average of my data was rather accurate. To find the percent error, this formula was used:

Percent Error = ? theoretical value - actual value ? � 100

Theoretical value

My percent error for beta, gamma, and delta kernels was 0.90%, 4.46%, and 13.5% respectively. (See calculations in appendix)

See Table 2 - Percent Error

This percent error could have occurred while massing. Since there were several balanced used instead of just one, the masses could have differed. One balance was used for the kernels, while the beaker mass was found using a separate balance. The different balances could have lowered the accuracy of the masses. Another place where mass could have been inaccurate was when the popcorn was popped. Sometimes the popcorn was burned, while other times the popcorn was popped perfectly. If the popcorn was burnt, the mass was lowered by the release of CO2. Also, the duration of the heating of the popcorn was inconsistent. Since the popcorn of the same technique would still pop at different rates, it is impossible to control the time of the heating. But the longer the beaker is heated, the longer the oil inside is also heated and evaporating.

So the longer the beaker is heated, the more gas escapes and the lower the mass will be, which will increase the percentage of water in the popcorn. Also, while the beakers were cooling off, some of the moisture could have been collected back in the beaker since the foil was not always taken off immediately. This would have added to the mass and lowered the percentage of water. To improve this lab, only one lab balance should be used during the entire experiment. Also, more care should be exercised when popping popcorn so that the popcorn does not burn. This could be done by lowering the heat and shaking the popcorn inside the beaker. Also, the foil on the beaker should be removed immediately after heating.

In this lab, I discovered that more water in a kernel does not necessarily mean that it will produce larger popcorn, as I had initially had predicted. Ultimately, based on my data and the class average (theoretical value) 15-16% water in a kernel produces the best popcorn. I learned that the amount of water in the kernel affects the rate at which the kernel pops, more than it affects the size of the popped corn.