Chemistry of Cooking

Student Activities Popcorn Science

Introduction

Phenomena-Popcorn

Day 1 Activating Prior Knowledge

Warm up activity: Supply each student with a piece of 8 1/2 by 11 inch scrap paper, blank on one side. On it, have them label three columns: know, sense data, questions, but instruct them not to put their names on the paper. Give students 3 minutes to write down as much as they can in the know column about popcorn and any questions that they might have in the third column. For the students who respond “I don’t know anything” or “I don’t have any questions” prompt them by asking them to think back on the last time they either ate or saw popcorn. Then show a clip of an old style popcorn ad either from a drive-in, movie theater, or school house rock.

Then teacher makes the popcorn using a non-microwave method. Depending on resources available it could be a stand-alone popper, either oil or air, jiffy pop over a hot plate, a regular lidded pan with kernels over a hot plate or the specialized cookware needed with an induction burner. Most students have only had popcorn at the movies or from a microwave so they will be interested in the cooking as well as the prospect of eating. As the process occurs, ask students to note what they see, hear, or smell as well as any additional questions that come to mind. Give two minutes at the end for students to add to notes. Then have students do a “popcorn” share. Each student crumples up his/her paper, form a circle and then “pop” the corn by tossing papers in the air into the center of circle. Repeat 2 times and then have students open up and share what is on the paper in front of them. While passing out the popcorn, have students write any questions from the claimed paper on a sticky note and add to a class chart. Show students the short video of the popcorn expanding and then ask them to explain the phenomena. Use I think, he thinks, we think strategy where each student writes their explanation; then students partner up and restate their partner’s explanation; then they come up with one explanation to present to the group.

Day 2 and 3 Investigating the Influence of Water on Popping Rate

Warm up activity: Have students discuss ways with their shoulder partners to prove that the amount of water inside the pericarp affects how the popcorn pops. Through Socratic questioning techniques, lead them into the following experiment. Working in teacher-selected heterogeneous groups of three to four students with clearly defined roles, students will carry out the following experiment. Students will count out 6 bags of 50 kernels each of the same type of un-popped corn. They will weigh and record the starting weights of each bag. Three of the bags will be the controls, three of the bags will have 20 ml of water added, and three will have their contents removed, put in a 200 degree oven for an hour, allowed to cool and then replaced in the bag. On day 2, students will reweigh each of the three bags, after pouring off and measuring any remaining water. There should be a difference in weight. The soaked seeds should weigh more, the dried seeds less and the control should be the same. Students will then try to pop each of the six batches using the same method. They are collecting three pieces of data for each sample: the percentage popped, the average kernel size (measure a random line of 10 using centimeters, then divide) and the total popped volume. Depending on the readiness of the students, different averages could be considered. It would make sense to use the mean for volume and length as both can be fractional parts whereas it doesn’t make sense to use it for number/percentage popped. Students could also use the median for all three. Again depending on the readiness of the students, students could create bar graphs for each category. More mathematically advanced students could create box and whisker plots which will show how reliable the data are.

Day 4: Claim, Evidence, Reasoning Literature/Experiment Connection

Students will read the New York Times article²² and evaluate for bias. They will then take part in a double blind teacher designed experiment to evaluate claims from within the article. Students will collect qualitative data in the form of taste preference and quantitative data in the form of volume, popped kernel size, and percentage of kernels popped. They will then write a persuasive essay either supporting or refuting the content of the article using experimental evidence.

Days 5-14 Investigating Water and Change of State

In this middle part of the unit, the focus switches from popcorn and the change of state of the water in the kernel to a much broader look at the relationship between energy, temperature and change of state, using water as the medium.

Water Investigations

Part 1: Hot—demonstrating that heating water causes it to bubble and then turn into steam so that eventually all of the water will be gone from the container as the gas expands to fill the area. To raise the rigor, have students collect temperature readings and graph over time and/or measure the amount of water remaining after a few minutes of boiling and/or do in a pot with a clear lid so that students can see the water vapor condensing. This first set of water experiment links to popcorn by letting students see what is happening inside the kernel. To demonstrate that the water vapor takes more room and so increases the pressure inside the hull, attach a non-latex glove securely to the mouth of a flask. As the water changes phase, the glove will inflate. Adding rice to a clear pot will allow the students to see more clearly how the hottest water rises but then starts to cool as it moves away from the heat source and begins to fall back down lacking the energy to transition to water vapor. This cycle is repeated until all of the water reaches the required energy state. On a side note, the rice experiment will also help students develop an understanding of plate movement due to the very slow movement of magma under the crust.

Part 2: Cold—fill a plastic container to the top with water, lay the cover on top but don’t seal it, put in the freezer and check the next morning. This activity helps students to discover that water expands when it freezes and that if you let the ice thaw it will fit back into the container. As an extension, have students fill plastic water bottles to the very top and put them in the freezers. In most cases, the ice will expand enough to crack the plastic bottle. This demonstration of filling, freezing and cracking sets students up to understand frost wedging as a principle force of weathering later. This is a good place to look at the molecular structure of water and have students make simple models using toothpicks and marshmallows. More advanced students could consider the valence models of the two elements, and their electronegativity patterns from the periodic chart. This is also a good place to revisit the idea of density. In elementary school, students develop the idea that heavy things sink and lighter things float. In middle school, that understanding is expanded to include the idea of density. Heavy things can float as long as their overall density is less than the substance in which they are floating. The phenomenon of water floating on water is a great entry point. Students can then build density columns using only water, food coloring, and either salt or sugar. As in the heat experiment, students can also collect temperature data over time as a cup of ice changes state to room temperature water. Since my students will all have Chrome books this year, I will incorporate technology by using temperature probes and the Sparkvue software that will collect and graph temperature changes over time. It will allow students to see that there isn’t a temperature change until there is a complete phase change.

Part 3: Heat by the Numbers—why do animals huddle together in the cold? This set of experiments is designed to help students discover that heat energy always moves from higher energy to lower energy, hot to cold. To start, heat water until it steams. Then stop and pour into a jar, cover with plastic wrap, and then take the temperature every two minutes until there is no change over three successive readings. Repeat experiment but this time do it with four jars that touch, wait until the four are at the same temperature as the one, then record temperatures every two minutes. Continue until the four jars match the temperature of the one jar. Students can then graph both sets of data as temperature compared to elapsed time. The last experiment gets into the idea of surface area. It isn’t that heat is only being lost on the outside. It is that the temperature difference is much less where the surfaces are touching. A variation would be to use five jars, one in the center and four outside and note any differences. To demonstrate that different substances react to heat and cold differently, students could investigate how other substances, like most metals, expand when hot but contract when cold. The differing expansion of metals when heated is behind most thermostats, including the ones found in many popcorn poppers. To discover that water is not the only substance that expands when cooled, students should do the following rubber band experiment. Suspend a paper clip in a shoebox from a rubber band at room temperature and mark the placement. The box assembly is then put in the refrigerator for 20 minutes and then the clip position is marked. Lastly, the room temperature rubber band is heated with a hair dryer for 5 minutes and then the clip position is marked. Students will see that although most substances get larger when they are heated and smaller when they are cooled (think of how we demonstrate increased kinetic activity) rubber bands do the opposite.

Part 4: Engineering a Solution—putting it all together.

Using what they have learned about the transfer of heat energy from hot to cold, students will work in groups to create an insulated drink cooler from commonly found materials. Each group will start with the same size ice cube in a small paper cup. In order to monitor the state of the ice cube, the cooler must have an easily removable and replaceable lid. Students will have to create a design plan before they “shop” for materials. Whenever I give a design challenge, I try and provide a variety of items, some that I know will be more useful than others but I still let students decide. For this challenge, items would include cups of different sizes in paper, plastic, and Styrofoam. Fastening materials would include glue, scotch tape, masking tape, duct tape, string/yarn and a stapler. Insulating materials would include old file folders, plastic wrap, aluminum foil, wax paper, bubble wrap, plastic straws and pieces of material-cotton, wool, and synthetic blends. Paper would be available in both copy weight, construction and cardstock in a variety of colors. As in the real world, there are different costs associated with each. Styrofoam, aluminum wrap and duct tape will be more expensive than file folders, plastic wrap and masking tape. The “coolers” will be tested outside on the tennis courts. Graphic design is a huge thing in middle school. Different colors and types of paper will be available for decorating their containers. Although I won’t talk directly about color and heat absorption, some students may have background knowledge from elementary school. As part of the weather kit in first grade, students took temperature readings of thermometers left in the sun in either white or black sleeves. For each item chosen, students have to justify why that material was selected. An example might be that even though Styrofoam is four times the cost of the file folder, it is a better insulator and is also water tight. The winning container will have the longest ice cube melt time at the lowest cost. This is similar to another activity that comes later in the semester when students create earthquake resistant houses. To encourage students to do more thinking in the design phase rather than guess and try, I institute fees for both additional shopping trips and restocking.  

Days 15-19 Student Designed Investigation

Students design, conduct, and analyze the results of a question of their own choosing connected to popcorn. This investigation has been broken down into several parts as shown.

The Science of Popcorn

Students will use the science and engineering practices of the NGSS to investigate a question of their own choosing connected to the science of popcorn.

Students have a choice to share their work as a power point/Google slide presentation, a poster, a written lab report, an oral presentation with visual aids or another format discussed with and approved by the teacher.

My topic is:

I plan to share my work as:

Teacher’s signature

Step 1: Generating a Testable Question

What would you like to know? Question needs to relate in some way to popcorn.

Requires Teacher signature before moving on to next step.

_______________________________

Step 2:  Personal Background Knowledge

What do you think you already know about this topic that might help you form your hypothesis? Write three to five sentences in one paragraph about your prior knowledge before you do any other background research.

Requires Teacher signature before moving on to next step.

_______________________________

Step 3: Background research

Your work must be at least two paragraphs of four to six sentences. It must contain at least four facts and details related to your topic. Information needs to be in your own words and not just copied and pasted from your sources. You need to use and cite at least 2 sources. Sources may include books, web sites, videos, articles and/or interviews with experts in the field. Make sure that your source is credible. Wikipedia may only be used as a starting point to get sources; it does not count as one of your two sources.

Requires teacher signature before moving on to next step.

_______________________________

Step 4: Develop a Testable Hypothesis related to the Topic of Popcorn

This may differ from your original testable question. Remember a testable hypothesis is a statement that can be supported by data.

Requires Teacher signature before moving on to next step.

_______________________________

Step 5: Design an experiment to test your hypothesis. Describe any anticipated safety issues and how you plan to address them.

Be sure to only look at one variable at a time and keep the other variables the same. Include clearly labeled data table(s) with units. Remember multiple trials. My goal is for students to do their investigations in the classroom. I will have heat sources and a microwave available. I will also provide basic popping corn. Since they are student designed, it may be possible that a home component is needed. If that is the case, it needs to be approved by both the parents and myself in this stage of the project.

Requires parent signature before moving on to next step.

_______________________________

Step 6: Conduct your experiment. Prior to doing any experiments, we will review the science safety rules.

Gather the data.

Requires teacher signature before moving on to next step.

_______________________________

Step 7: Analyze your data.

What patterns do you see? How can you use graphs, pictures and math to better convey your findings?

Requires teacher signature before moving on to next step.

_______________________________

Step 8: Write your Conclusion

Revisit your hypothesis. Do your data support or not support it? What is your evidence? How does the evidence connect to your claim?

Step 9: Experimental Notes

Reflect qualitatively on the experience. What, if anything, happened that you didn’t anticipate? What affect do you think it had on your results?

Step 10: Next Steps

Based on what you learned from this experiment, what question would you like to investigate next? Write a brief three to five sentence paragraph about your new question and possible investigation.

Popcorn Science Investigation Ideas (Scaffolding for students who are unable to generate their own question)

Possible Questions:

Which pops more, Orville Redenbacher or Paragon?

Options-microwave, pot on “stove”, table top popcorn maker

Which pops bigger, Orville Redenbacher or Paragon?

Options-microwave, pot on “stove”, tabletop popcorn maker

-bigger in average popped kernel size or bigger in total volume

Which heat source pops loose corn better?

Options-microwave compared to either pot on “stove” or tabletop popcorn maker

How does using oil affect the amount of kernels popped?

Options-pot on “stove,” tabletop popcorn maker

How does using oil affect the size of kernels popped?

Options-pot on “stove,” tabletop popcorn maker

-bigger in average popped kernel size or bigger in total volume

How does the type of oil affect the amount of kernels popped?

Options-corn, canola, coconut

How does the type of oil affect the size of kernels popped?

Options-corn, canola, coconut

-bigger in average popped kernel size or bigger in total volume

How does the type of oil affect the taste of kernels popped?

Options-corn, canola, coconut

Scoring Rubric for Popcorn Science Investigation

Students are to design, conduct and analyze the results of an experiment of their own choosing connected to Popcorn. The plan is to do the bulk of the work in class. There are built-in checkpoints along the way.