Exploding Corn: Student Pages DIFFERENCES BEWEEN MASS AND VOLUME CHANGES WITH POPCORN

Size: px

Start display at page:

Download "Exploding Corn: Student Pages DIFFERENCES BEWEEN MASS AND VOLUME CHANGES WITH POPCORN"

Alexander Nelson
6 years ago
Views:

EXPERIMENT 2: Exploding Corn: Student Pages DIFFERENCES BEWEEN MASS AND VOLUME CHANGES WITH POPCORN BACKGROUND According to The Popcorn Board, Americans today consume 17 billion quarts of popped

1 EXPERIMENT 2: Exploding Corn: Student Pages DIFFERENCES BEWEEN MASS AND VOLUME CHANGES WITH POPCORN BACKGROUND According to The Popcorn Board, Americans today consume 17 billion quarts of popped popcorn each year (see The average American eats about 52 quarts of popcorn per year. Think about that the next time you sit down for a movie with a big bowl of popcorn. The science behind corn popping is as simple as boiling water. Each popcorn kernel contains starch and water. The kernel needs to have a moisture content around 14% in order to have the fuel to pop. The starch grains of the popcorn are enclosed in a pericarp, or seed, covering (see Figure 2.1, p. 20). When the kernel is heated, the starch grains gelatinize in a gooey substance and the water begins to boil inside the pericarp and starchy endosperm. As the water temperature reaches the boiling point of water, the water vaporizes and expands rapidly in volume. The hard starch matrix holds until the pressure becomes too great at 135 pounds per square inch, at which point the kernel bursts open and the endosperm expands in volume because of the pressure difference. The water evaporates and the cooked starch granules are dried out, making the endosperm light and crisp. If the moisture cannot escape, it gets reabsorbed by the popped corn making it chewy and tough. Pressure, explosions, and phase changes who knew that popping corn was so intense? This experiment will give you a chance to watch the action occur in front of your eyes while you consider the overall energy and mass of the popcorn. Does the mass stay the same, increase, or decrease as it goes from kernel to popcorn? How can you measure this throughout the experiment? GOURMET LAB: THE SCIENTIFIC PRINCIPLES BEHIND YOUR FAVORITE FOODS 19

Figure 2.1: Anatomy of a corn kernel. HYPOTHESIS For this experiment, you will be measuring the overall mass of the corn as it goes from kernel to popcorn.

2 Figure 2.1: Anatomy of a corn kernel. HYPOTHESIS For this experiment, you will be measuring the overall mass of the corn as it goes from kernel to popcorn. What do you predict will happen to the mass during the experiment? Make a hypothesis stating how the mass will change, with an explanation of why you think that change will occur. Next, consider how you think the volume will change. Make a hypothesis stating how the volume will change, with an explanation of why you think that change will occur. 20 NATIONAL SCIENCE TEACHERS ASSOCIATION

3 MATERIALS NEEDED PER GROUP 30 Zea mays everta in pericarp covering (popcorn kernels) 5 ml of liquid vegetable lipids (vegetable oil) 0.25 g of sodium chloride, NaCl (salt) Erlenmeyer flask, 250 ml Beaker, 250 ml Graduated cylinders Aluminum foil, 10 cm 10 cm square Toothpick Paper towel Bunsen burner Ring stand with wire mesh Pair of flask tongs Balance Indirectly vented chemical-splash goggles Aprons PROCEDURE 1. Read through the entire Procedure section before beginning. 2. Put on your safety goggles and apron, and gather all your materials at your lab station. If you notice that any of the materials are dirty or discolored, notify your teacher. 3. Take the 250 ml Erlenmeyer flask. Make a cover for the opening of the flask using a small square of aluminum foil. (Safety note: Do not use a stopper when heating the flask.) 4. Poke three or four small holes in the top of the aluminum foil with a toothpick. 5. Using the balance, find the mass of your flask with the foil lid and record the mass in your data table for balance measurements. 6. Add 5 ml of liquid vegetable lipids to the flask. 7. Using the balance, find the mass of the flask, liquid vegetable lipids, and cover and record in your data table for balance measurements under My Results. 8. Place 30 kernels of Zea mays everta in a small graduated cylinder. Record the approximate volume of the kernels in your data table for volume measurements. GOURMET LAB: THE SCIENTIFIC PRINCIPLES BEHIND YOUR FAVORITE FOODS 21

4 Figure 2.2: Bunsen burner and ring stand. 19. Carefully remove the cover from the flask and add the 30 kernels to the flask. 10. Using the balance, find the mass of the flask, foil cover, liquid vegetable lipids, and Zea mays everta and record that mass in your data table for balance measurements. 11. Set up a Bunsen burner and ring stand with wire mesh on the iron ring. Make sure your Bunsen burner gas intake tube is securely connected to the gas nozzle and that the ring is set about 3 in. above the barrel of the burner (see Figure 2.2). Light the Bunsen burner to create a flame that is no more than 3 in. high. 12. Using the tongs, move the flask across the flame to evenly heat the Zea mays everta. 13. As the Zea mays everta burst, remove the flask from the heat and then heat only gently to pop the remaining kernels. Some kernels may not pop, so take care not to burn the popcorn. What do you observe inside the flask as the kernels are popping? Record your observations here: 22 NATIONAL SCIENCE TEACHERS ASSOCIATION

5 14. Allow the flask to cool to room temperature. Use the balance to find the mass of the flask, lid, and contents and record in your data table for balance measurements. 15. Transfer the Zea mays everta to the 250 ml beaker. Record the approximate volume and appearance of the popped corn in your data table for volume measurements. 16. Compare your results with another lab group in the class. Record the other data on balance measurements and volume measurements in the data table column listed Results From Other Scientists for analysis. 17. Pour your popped Zea mays everta onto a paper towel. Sprinkle with sodium chloride for taste, and then feel free to eat your final lab product. 18. Clean your lab table and answer the Data Analysis and Conclusion and Connections questions below. DATA AND OBSERVATIONS Balance Measurements Mass of flask and cover (step 5) My Results (g) Results From Other Scientists (g) Mass of oil, flask, and cover (step 7) Mass of flask, cover, oil, and Zea mays everta in pericarp (step 10) Mass of flask, cover, oil, and Zea mays everta after heat expansion (step 14) GOURMET LAB: THE SCIENTIFIC PRINCIPLES BEHIND YOUR FAVORITE FOODS 23

6 Volume Measurements Volume of Zea mays everta in pericarp (step 8) Volume of popped Zea mays everta after heat expansion (step 15) My Results (ml) Results From Other Scientists (ml) DATA ANALYSIS For each of the following questions, be sure to explain using detail and complete sentences. If the question requires you to complete calculations, show all of your work. 1. What was the overall mass of oil used for your experiment? Calculate this using your measurements from the Balance Measurements data table. 2. What was the mass of the Zea mays everta used in the experiment? Use your measurements from the Balance Measurements data table, and your answer to Data Analysis question 1 to help you solve for this value. 3. What was the mass of the Zea mays everta once it was popped? Use your measurements from the Balance Measurements data table to help you solve for this value. 4. What was the change in volume of the Zea mays everta from kernel to when it popped? Use your measurements from the Volume Measurements data table to help you solve for this value. 24 NATIONAL SCIENCE TEACHERS ASSOCIATION

7 CONCLUSION AND CONNECTIONS 1. How are volume and mass different? How are they similar? Use the Venn diagram below to describe mass and volume. Use the intersection of the two circles to explain how they are similar. Mass Volume 2. How do your results compare between the two trials and with other groups in the class? Explain any potential differences in the data. 3. Why do we use oil instead of water to heat the Zea mays everta? 4. Why do you think that some of the Zea mays everta did not pop? GOURMET LAB: THE SCIENTIFIC PRINCIPLES BEHIND YOUR FAVORITE FOODS 25

Used to pick up or hold hot objects Protects the eyes from flying objects or chemical splashes

Chemistry Ms. Ye Name Date Block Do Now: Name that equipment! Label the piece of equipment appropriately. Not all names will be used. Object Name Used For Used to pick up or hold hot objects Protects the