Lab Activity- no report required
Name:______________________
Percentage of Water in Popcorn
Purpose: To determine the amount of water in a sample of popcorn.
Theory: Popcorn, a cereal grain like wheat or oats, is about 75% carbohydrate (starch) with smaller
amounts of protein, fat, minerals, and water. The water plays a critical role in the popping process.
When heated, the moisture inside the kernel turns into steam. The hard outer covering of the kernel acts
like a seal, causing a build-up of pressure inside the kernel. When the pressure gets high enough, the
kernel explodes and the starch rapidly expands to create the fluffy “flower” or popcorn. To ensure
maximum popping expansion, the corn is carefully cured (dried) until it reaches a certain percentage of
water, which you will determine in this lab.
Procedure:
1. Make a popcorn popper out of two foil bowls using one as a lid and fastening them together with 2
clips.
2. Add a small amount of oil. Measure the mass of popper and oil (including clips).
3. Add 20 kernels of popcorn and use the clips to fasten the lid to the base. Measure the mass of the
popper, oil, and corn.
4. Pop the popcorn on a hotplate until all kernels have popped. IMPORTANT: Use the crucible tongs
to keep the popper moving to avoid scorching. If the heat is too high, raise the popper above the
hotplate. DO NOT BURN THE POPCORN.
5. Let the popper cool. Measure the mass of popper, oil, and popped corn.
6. Dispose of the popcorn as appropriate. Sodium chloride is available.
7. Repeat the procedure for trial 2.
8. Clean the popper (wipe it out with paper towel) and save it for the next class.
Data:
Trial 1
Trial 2
Mass of popper, clips, and oil (g)
Mass of popper, clips, oil, and popcorn
(before popping) (g)
Mass of popper, clips, oil, and popcorn
(after popping) (g)
1
Calculations:
1. For each trial, calculate the mass of the unpopped corn.
Trial 1________________________Trial 2________________________
2. For each trial, calculate the mass of water in the unpopped corn.
Trial 1________________________Trial 2________________________
3. For each trial, calculate the percentage of water in popcorn.
Trial 1________________________Trial 2________________________
4. If two trials were performed, calculate the average percentage of water in popcorn.
___________________________________________
Conclusion:
1. Explain what makes popcorn pop in your own words.
When heated, the (liquid) water inside of the kernels turns to water vapor. Water vapor takes up more
space than liquid water, so this expansion of the gas inside the kernels causes them to explode.
2. State whether the following errors would make the calculated percentage of water higher or lower.
Explain your reasoning.
 Unpopped kernels
Percentage of water would be lower . The popped corn would have a higher mass (water
inside the unpopped kernels  lower value)

Too much oil – some burns off as smoke:
Percentage of water would increase. The mass of the popped kernels would decrease, causing
the water value (in unpopped kernels) to go up.

Eating some popped corn before the final weighing
2
Percentage of water would be higher (extra water in unpopped kernels)

Adding salt before the final weighing
Percentage of water would be lower because the popped corn would have a higher mass (Salt added)
Kool Aid Lab
1. Calculate how much solid Kool-Aid you will need to make 0.1 L of each
solution. (Hint 1: Kool-Aid is mostly sugar (C6H12O6), so you can assume
that the “molar mass” of Kool-Aid is the same as the molar mass of
sugar.) (Hint 2: “What you know” is the volume – 0.1 L)
Show all of your calculations below. Circle or box the answer for each part.
The “molar mass” of Kool-Aid: 6 x 12 = 72 , 12, 6 x 16 = 96 180g/mole
Mass of Kool-Aid needed for 0.1 M solution:
.1 moles sugar x 180 = 18.0 grams/ 1 Liter of solution
Mass of Kool-Aid needed for 0.4 M solution:
.4 moles sugar x 180 g/mole = 72.0 grams/ 1 Liter of solution
Mass of Kool-Aid needed for 0.7 M solution:
.7 moles x 180 g/mole  125.0 grams/ 1 Liter of solution
Observations of the 0.1 M solution:
3
Observations of the 0.4 M solution:
Observations of the 0.7 M solution:
Questions:
1. Which concentration that you tested was closest to the ideal concentration of
Kool-Aid? What was wrong with each of the other solutions that you made?
2. How is taste related to concentration? Why are they related in this way? As
the concentration increases, the taste becomes sweeter (The taste improves)
because more and more sugar is added.
4
5