Aleksza
Honors Chemistry
Percentage of Water in Popcorn
2013-14
(adapted from: http://ths1.ttsd.k12.or.us/departments/science/sci_staff/rmassey/chem/percentage_popcorn2.pdf)
Background:
Popcorn pops because of the natural moisture inside each kernel. When the internal
water is heated above 100°C, the liquid water changes to a gas, which takes up much
more space than the liquid, so the kernel expands rapidly.
The percentage of water (H2O) in popcorn can be determined by the following equation:
𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑚𝑎𝑠𝑠 − 𝑓𝑖𝑛𝑎𝑙 𝑚𝑎𝑠𝑠
∗ 100 = 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑖𝑛 𝑢𝑛𝑝𝑜𝑝𝑝𝑒𝑑 𝑝𝑜𝑝𝑐𝑜𝑟𝑛
𝑓𝑖𝑛𝑎𝑙 𝑚𝑎𝑠𝑠
The popping process works best when the kernels are first coated with a small amount
of vegetable oil. Make sure you account for the presence of this oil when measuring
masses.
Materials:
Unpopped popcorn
Balance
Tongs
250 ml beaker
weighboats
hot hands
vegetable oil
hot plate
aluminum foil
Safety:
 Hot glass looks like cold glass, use proper heat precautions.
 The popcorn is for testing only, and must not be eaten.
 Splash goggles are to be worn for this lab.
Procedures:
1. Add a small amount of vegetable oil to a 250 mL beaker to coat the bottom of it.
Measure the mass of the beaker and oil. Record the mass in the Data Table.
2. Turn on the hot plate to a medium-high setting. (DO NOT SET TO MAXIMUM!)
3. Add 20 kernels of popcorn to the beaker. Shake the beaker gently to coat the kernels
with oil. Measure the mass of the beaker, oil, and popcorn. Record the mass in the
Data Table.
4. Cover the beaker loosely with the aluminum foil. Punch a few small holes in the
aluminum foil to let moisture escape. These holes should not be large enough to let the
popping corn pass through.
5. Heat the popcorn until the majority of the kernels have popped. The popcorn pops
more efficiently if the beaker is held firmly with tongs and gently shaken side to side.
6. Remove the beaker from the hot plate and allow it to cool for 10 minutes.
7. Remove the aluminum foil from the beaker and measure the mass of the beaker, oil,
and popped corn. Record the mass in the Data Table.
8. Shake the popcorn into a trashcan and clean the beaker with a small amount of dish
soap.
9. Repeat steps 1-7 two more times for a total of three (3) trials.
10. Turn off the hot plate. Clean the beaker and work area. Wash your hands
thoroughly before leaving the laboratory.
Data:
Before Heating
Mass (g)
Trial 1
Mass (g)
Trial 2
Mass (g)
Trial 3
Mass (g)
Trial 1
Mass (g)
Trial 2
Mass (g)
Trial 3
Mass of 250 mL beaker + oil
Mass of beaker + oil + 20 kernels
After Heating (removes water)
Mass of beaker + oil + popped kernels
Analysis:
Show work using correct units and box answer.
1. Calculate the average initial mass of the popcorn kernels.
2. Calculate the average final mass of the popcorn kernels.
3. Calculate the percentage of water in unpopped popcorn using the averages
found in 1 & 2.