Hot Popcorn
Phenomenon:
Popcorn pops when heated, increasing in volume and decreasing in weight.
Student Task:
Construct an explanation for what causes popcorn to pop when heated.
Model
Students develop and use a model to describe changes in particle motion when thermal energy (heat) is added or removed.
Investigate
Students plan and carry out an investigation to gather evidence that steam (water vapor) and pressure are required for popcorn to pop.
Obtain Information
Students read to obtain information about what causes popcorn to pop.
Analyze Data
N/A
Explanation:
Popcorn pops because pressure builds up inside the seed as water changes state from a liquid to a gas. Gases are made of particles that are moving, and when thermal energy (heat) is added to a system the motion of the molecules increases. Collisions between particles and with the walls of the seed result in a force called pressure. This pressure causes corn seeds to pop.
Optional STEM Project:
Students use digital tools (Hummingbird Duo + Scratch) to develop a model that explains how the addition of thermal energy (heat) increases the motion of particles in a gas.
NGSS Standard:
MS-PS1-4 Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
Utah SEEd Standard:
6.2.2 Develop a model to predict the effect of thermal energy on states of matter and density.
Recommended Teaching Sequence:
Day 1: Observe popcorn popping on two different time scales (i.e., real-time and in slow-motion). Ask questions about the cause of the changes in the system. Plan an investigation.
Day 2: Carry out an investigation to gather evidence that steam (water vapor) and pressure are required for popcorn to pop.
Day 3: Read to obtain information about how heat causes corn seeds to pop. Construct a written explanation for what causes popcorn to pop when heated.
Days 4-6: Develop and use a model to describe changes in particle motion when thermal energy (heat) is added or removed.
Formative Assessment:
Use what students have written in their science notebooks as a formative assessment, including observations, questions, data collected, model drawings, and written explanation for the phenomenon.
Do students understand that adding or removing thermal energy changes the motion of particles until a phase change occurs?
Lesson Contributors:
April Mitchell, Science Specialist, Salt Lake City School District
Charles Matthews, STEM Coordinator, Park City School District