Pressure in Popcorn Kernels
Background
When the water pressure inside a popcorn kernel is great enough, the kernel bursts and releases the water vapor. The ideal gas law can be used to find the pressure in the kernel as it bursts.
KNOW: What do you know about the ideal gas law?
Objectives
-analyze the pressure in a popcorn kernel using the ideal gas law
-calculate the pressure required to burst a kernel of popcorn
Materials
18-20 popcorn kernels, vegetable oil, wire gauze, Bunsen burner, ring stand, iron ring, 10ml graduated cylinder, 250ml beaker, hot gloves, balance, distilled water, paper towels, goggles
Procedure
1.Place 5ml of distilled water in the graduated cylinder.
2.Place 18-20 popcorn kernels in the graduated cylinder with the water. Make sure to tap the cylinder to get rid of any of the air bubbles on the kernels. Record the volume change:______
3.Remove the popcorn kernels and dry them with a paper towel.
4.Place the kernels in around 2ml of vegetable oil.
5.Measure the total mass of the beaker, oil, and kernels. Record this mass:______
6.Set up the Bunsen burner with a ring stand, ring, and wire gauze.
7.Gently heat the beaker on the wire gauze with one wire gauze covering the beaker.
8.After all of the popcorn is done popping, remove the beaker and weigh it AFTER it has cooled completely. Record this mass:______
Data-YOU MUST SHOW YOUR WORK TO GET CREDIT
1.Calculate the volume of the popcorn kernels in liters by the differences of the volumes of distilled water before and after adding the popcorn:
2.Calculate the total mass of water vapor released using the mass measurements of the beaker, oil, and popcorn before and after popping: This will be the mass of you water released from the popcorn!
3.Calculate the number of moles of water released from the popcorn by using the mass of water released and the molar mass of water according to the periodic chart.
4.Use the ideal gas law to calculate the pressure of the gas that was released from the popcorn. You will use the fact that the oil boils at 2250C. You will use the volume in liters and the moles you have already calculated.
WHAT: What did you learn about the ideal gas law?
Answer three of the analysis questions with complete sentences.
1.Compare the pressure you calculated for the pressure of the gas released from the popcorn kernel to atmospheric pressure:
2.Why did not all of the popcorn kernels pop?
3.Describe a source of error in this experiement:
4.Why did you need to use the liter unit instead of the milliliter unit in the calculation using the ideal gas law?
LEARN: What do you still want to learn about the ideal gas law?