The Popcorn Lab 37404h

THE POPCORN LAB Purpose: To determine (for various brands of popcorn) a) a) the water lost in popping b) b) the density of the unpopped kernel c) c) the pressure inside a kernel of popcorn … just before it pops! Materials: • 125 mL Erlenmeyer flask • 20 drops cooking oil (peanut) • 32 kernels of popcorn • medicine dropper • balance • 10 mL graduated cylinder • ring stand • iron ring • 2 wire screens • burner • clamp • small beaker or weighing dish

Procedure A: 1. Prepare a data table for the three readings of mass. 2. Add about 20 drops of cooking oil to the flask. Use a balance to find the mass, to the nearest 0.01 g, of the flask and the oil and record this in your data table. 3. Add 16 kernels of popcorn to the flask. Record the new mass, to the nearest 0.01 g, in the data table. 4. Place the flask on a wire screen on a ring stand. Clamp the flask to the stand. Place the second wire screen over the opening of the flask to keep the popping kernels in the flask. Hold the Bunsen burner and move it slowly back and forth under the flask. When you see the oil bubbling around the kernels, remove the heat for a few seconds. If no popping occurs, add a little more heat. DO NOT BURN THEM. 5. Let the flask cool after the kernels are popped. Record the mass. 6. Record your observations during the popping. Was there a gas coming out of the kernels? Calculations and Conclusions: 1. 1. Did the kernels weigh more before or after popping? If there was a difference, what was the value? 2. 2. Did you observe anything that would lead you to conclude that the weight loss was due to water? 3. 3. What percentage of the kernels popped? 4. 4. Assuming that all of the lost mass was due to water, and that all of the water was driven off, what was the percentage of water in the kernels that popped? 5. 5. Summarize the different brands – share your data with others in the class to obtain information about the percentage of water and % of kernels that popped. 6. 6. Is there a correlation between percent of water and percentage popped for the various brands? Explain. Procedure B: 1. 1. Prepare a data table for recording the masses and volumes below. 2. 2. Place a weighing dish or small beaker on the balance and find the mass of 16 kernels. Record the mass to the nearest 0.01 g.

3. 3. Place about 5.0 mL of water in a 10 mL graduated cylinder and record the volume to within 0.1 mL. 4. 4. Place the 16 kernels in the water in the cylinder. Did they sink or float? 5. 5. Record the volume of water plus kernels to the nearest 0.1 mL. Calculations and Conclusions: 1. 1. Is the density of unpopped kernels of popcorn greater or less that 1.0 g/mL? Explain – think about what you observed when the kernels were placed in water. 2. 2. Calculate the mass of 16 kernels of popcorn. 3. 3. Calculate the volume of 16 kernels of popcorn. 4. 4. Find the density of unpopped kernels of popcorn in g/mL. Is your density calculation consistent with what you observed when the kernels were placed in water? THOUGHTS ABOUT POPCORN!!!! 1. Why does popcorn pop? 2. What is the volume of one kernel of popcorn? 3. How many grams of water did you find in the average kernel? 4. The popcorn pops at the boiling point of oil (about 225°C). What would be the pressure of water inside the kernel of popcorn if all the liquid were vaporized and heated to 225°C? HINT – Use the Ideal Gas Law to calculate the pressure of water vapor inside a kernel at 225°C. Assume that the volume and mass for one kernel that you calculated in questions 2 and 3 are appropriate. 5. Use the Ideal Gas Law to calculate the pressure inside a kernel at room temperature. 6. Considering your answer to #5, do you think that a kernel would explode if it were broken at room temperature? If you can, use pliers to try this out. Explain. 7. Write a chemical word equation (no formulas) for popping corn.

8. What do you suppose makes popcorn kernels different from other corn varieties such as sweet corn or field corn?