Exploding Popcorn: Exploring How Internal Temperature Affects Mass and Volume (Part 1/2)

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Objective

SWBAT measure changes in mass and volume of a popcorn kernel.

Big Idea

Matter is all around us and is always changing. By investigating how popcorn changes when it is popped, students learn about mass and volume.

Introduction

Sometimes it is important to stop and smell the popcorn - and in this case, measure it and eat it too. Food-based labs are highly engaging for students because they are motivated by the future chance of "just one taste".  In this guided inquiry lab, we use many science practices to carry out an investigation for the purpose of improving measurement skills and understanding of the concepts of mass and volume. This lab is modified from the following book:

Young, S. (2011). Gourmet lab: the scientific principles behind your favorite foods. Arlington, Va.: National Science Teachers Association.

I use the Exploding Popcorn Lab as a way for students to solidify their understanding of matter and its properties at the beginning of our exploration of matter. By measuring mass and volume changes in this lab, students are able to prove that popcorn fits the definition of matter. This lab can also be used or re-used to explore many different concepts including: changes of state, the Law of Conservation of Mass, pressure as a force, thermal energy and the Law of Conservation of Energy. Rather than trying to teach all of these concepts at one time, I choose one or two of the concepts as learning objectives and tailor the discussions and conclusion questions to match the objectives.

The Exploding Popcorn Lab is a guided inquiry investigation including lessons taught over the span of 2 -3 days. To help manage the magnitude of this project, you will find the project split into 2 parts.

  • Part 1 includes the ENGAGE, EXPLORE and EXPLAIN components of the lesson; Time: 1 50-minute lesson. 
  • Part 2 includes the EXTEND and EVALUATE components of the lesson; Time: 2 50-minute lessons or equivalent block period.

Engage

15 minutes

In order to ENGAGE students in this lesson, I pop some popcorn, load it up with salt and butter, and place one popped and one unpopped kernel on each student's desk with the instructions "not to eat it". We then watch this video of popcorn popping in slow motion: Slow Mo Guys Popcorn Popping Video.

After the video, students make observations of the kernels on their desks and of the video. I prompt them with the question:

So, what is different between the kernel before and after it pops?

This prompt leads students to make observations and draw on prior knowledge about popcorn. The prompt also draws out connections to the concepts of mass and volume. Level of student background knowledge about these concepts will vary greatly. For this reason, offering students a quick tutorial for illustration may prove beneficial:

Once these concepts are introduced, together, we look at the question we are going to answer during the lab:

How does increasing the internal temperature of a kernel of popcorn (Independent Variable = IV) affect the mass and volume of the popcorn (Dependent Variable = DV)?

This question is found on the Exploding Popcorn Experimental Design Plan. Students are each given their own copy of the plan. As a whole group, we dissect the question to clarify unknown vocabulary and the nature of the what the question is really asking.

Explore and Explain

35 minutes

The EXPLORE stage of the lesson is to get students involved in the topic so that they start to build their own understanding. To help students explore, they read a one-page Exploding Popcorn Background Information text together in lab groups. I encourage them to look up unknown vocabulary terms as they read and ask each other questions to clarify their understanding.

The EXPLAIN stage provide students with an opportunity to communicate what they have learned so far and figure out what it means. Students explain what they learn in the Background Research section of the Exploding Popcorn Experimental Design Plan by writing three facts relevant to the lab as seen here: Exploding Popcorn Investigation Experimental Design Plan Student Work.  During this time, I circulate through the lab groups to check for understanding and ask for student summaries of the main idea of the lab, and specifically if they were able to extract information from the background information about how popcorn pops.

While students have not conducted the investigation yet, an effective strategy to help students make sense of what is occurring during the popping process, and in turn, write a good hypothesis, is to have them draw a flowchart diagram of the stages the popcorn progresses through as it pops. I ask them to include labels and explanations to start and modify their flow charts as they move through the investigation. For additional explanation of this diagram, refer to the reflection for this section - Explaining Through Diagrams.

For a student explanation of the popping process that can be charted, view this video:

Continue on to Exploding Popcorn Lab Part 2.