May 19, 2023
Electric Crystals, Part 4
Electric Crystals and their Broken Symmetries

Students learn how some crystals produce electricity when squeezed (by the piezoelectric effect). Students perform calculations and explore engineering applications of piezo-devices to deepen understanding and engagement. This lesson is part 4 of a 4 part series. 

Grade levels: 6th grade - 8th grade , 9th grade - 12th grade
Approx time: 45 minutes
Things you'll need:
Step 1

Crystals' Shocking Properties

One of crystals' seemingly magical properties: the piezoelectric effect!

The comic introduces the concept of piezoelectricity: the phenomenon where a mechanical deformation results in a small charge on the surface of a crystal.

piezoelectric: mechanical deformations result in a small electric charge

Step 2

Dipole Moment

Learn about dipole moment of a configuration of charges.

Read the worksheet's explanation of dipole moment, and how geometry affects electric charge just as much as charge magnitude does. Students are guided through an example dipole moment calculation for an undeformed NaCl configuration. They're then prompted to calculate the dipole moment for the SiO2 configurations.

dipole moment: quantifies the strength a charge separation, can be detected as an electrical signal

Step 3

Symmetry is Key

Check in with a video about the effects of symmetry on crystal properties.

In this video Madelyn explains the source of piezoelectricity and how the symmetry of atoms inside a unit cell determines whether the material is piezoelectric. Students will then reflect on their NaCl and SiO2 calculations with this new explanation in mind.

Step 4

Identify the Device

Based on schematic diagrams, determine the identity of devices with piezos.

The properties of piezoelectric crystals mean they can be used as a a sensor or an actuator. Listed in a wordbank are six devices which use actual piezos. Students will use the wordbank to determine which devices are represented by the schematic diagrams.

Step 5

The Crystal Factory Feedback Form

Please fill out the survey to leave feedback for The Crystal Factory employees.

On this feedback form students can reflect on their favorite part of the tour, any remaining questions, and topics they're excited to learn more about. The comic ends with Krista geeking out about the amazing applications of symmetry and crystals, and the students on the tour seem to really get the message!

Why it Works

Supplemental materials for teachers can be found at the Galactic Polymath website, where you will find information on learning standards and be able to provide feedback on the lesson.

Don't stop here! This is part 4 of a series! Make sure to check out:

What is a Crystal, Anyway? (Electric Crystals, Part 1)

Unit Cells and Their Molecular Building Blocks (Electric Crystals, Part 2)

How do Crystals get their Shapes? (Electric Crystals, Part 3)