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Percent Composition in Popcorn
Name:_______________
INTRODUCTION: Why do corn kernels pop? 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
Vocabulary Terms :
 Percent Composition is the mass of the particular element or compound found in a
substance divided by the mass of the whole substance multiplied by 100. For
example, the percent composition of hydrogen (H) in water (H2O) is (2 / 18) (100)
which is 11.11%. This means that 11.11% of the mass of each water molecule is
accounted for by hydrogen.

Percent Error is a measure of the difference between your experimentally obtained
value and the accepted literature value or theoretical value.
PROBLEM:
What percent of water is in popcorn kernels?
Hypothesis:
________________________________________________________________________
Procedure:
1. Find mass of 250mL beaker. Record in chart.
2. Take 10 kernels of popcorn and place the kernels in a 250ml beaker. Find the mass of
beaker and unpopped popcorn. Record in chart.
3. Determine the mass of the unpopped kernels.
4. Pop the kernels by placing over the heat and moving the beaker using a pair of tongs.
**Do not allow the kernels to sit or they will burn and not pop.
5. After popping wait for the kernels to cool and measure the mass of the beaker and
popped kernel. From this you can determine the mass of the popped popcorn.
6. Determine the mass of the water in the kernel by finding the difference in mass
between the unpopped and the popped kernels of corn.
7. Calculate the percent of water in the kernel. (The % water in the unpopped
corn is found by dividing the grams of water by the mass of the
unpopped corn and then multiplying by 100.
Data: grams
Mass of
beaker
Mass of
beaker and
unpopped
kernels
Mass of just
the
unpopped
kernels
Mass of
beaker and
popped
Kernels
Mass of
popped
kernels
only
Mass of
water
Percent Composition in Popcorn
Name:_______________
Calculations:
1. What is the percent of water in popcorn? (Show calculations below.)
2. What is the percent error? (Accepted: % water in kernel is 10%)
(Show Calculations below)
3. What is the molar mass of the water H2O (Show your work below.)
4. Convert the mass of water to moles. (Show your work below.)
5. How many molecules of water are in the popcorn? (Show you work below.)