Grade Levels: 6-8

In this lesson plan, adaptable for grades 5-8, students play Crystal Cave, a game that challenges them to arrange molecules of different shapes and properties into an ordered, stable configuration. Through play, students explore and deepen their understanding of molecular stability,  ionic charges, crystal defects, and spatial patterning.

Lesson Plan Common Core State Standards Alignments

Lesson Plan Next Generation Science Standards Alignments

Students will:

  1. Learn that crystals are formed from tightly ordered molecules that occur in nature.
  2. Place virtual molecules of different shapes and properties into an ordered, stable configuration.
  3. Recognize that neutralized charges (+ and -) increase stability.
  4. Learn through play how some crystals have defects in the molecular pattern.


  • Computers or other devices with Internet access
  • Interactive whiteboard
  • Crystals (optional)


This lesson plan features a game called Crystal Cave, developed by our partner,  Field Day Lab. In this game, students apply their knowledge of molecular stability, ionic charges, crystal defects, and spatial patterning by placing molecules of different shapes and properties into an ordered, stable configuration -- a crystal.

Preview and play Crystal Cave to plan how you will adapt it to your students’ needs. If students will be playing in small groups, review tips on Setting Cooperative Gaming Expectations.

Read Crystal Cave: SnapThought Prompts for more information and specific SnapThought prompts to provide students during game play.

Assign Crystal Cave to the whole class using the Assignment Builder.

Depending on your classroom routines and available technology, you may want to consider these grouping options:

  • 1:1 with students and devices
  • Two to three students sharing one device and swapping ideas and the device back and forth
  • Station model where small groups rotate through using the devices
Build background knowledge or reinforce topics with these BrainPOP movies: Crystals, Rock Cycle, Types of Rocks, Salt, Mineral Identification, and Periodic Table of Elements.

Lesson Procedure:

  1. If you were able to bring in crystals, allow time for students explore them either by placing them at a central station or passing them around the class. Then, have students share what they know about crystals, such as what they are, examples of crystals in everyday life (e.g., jewelry, salt, sugar), how they form, etc. Make sure students understand that a crystal is a solid with molecules arranged in a stable, repeating pattern.
  2. After sharing what they know about crystals, play the BrainPOP movie Crystals on the whiteboard or other display. Pause the movie as Tim defines key terms to ensure students understanding.  
  3. Project the game Crystal Cave on the whiteboard or other display. Tell students that in this game, they will fill a space with tightly packed molecules to create a stable pattern as appears in crystals. They will also discover that pairing neutralized charges (+ with -) will further increase stability. Finally, they’ll learn that some crystals have defects in the molecular pattern.   
  4. Model the game by playing the first level as a whole class. Invite volunteers to come up and experiment with filling in the molecules and changing their orientation.
  5. Now have students return to their computers and instruct them to open the Crystal Cave assignment. Circulate as students play and help as needed. If students have individual logins through My BrainPOP, encourage them to use the SnapThought® tool to take snapshots and describe their thinking as they play.  For suggested prompts, see Crystal Cave: SnapThought Prompts.  
  6. After everyone has played, bring the class together to discuss and review what they learned, including how geometric arrangement and charges affect a crystal’s stability. If students used SnapThought, encourage them to share their reflections.

Extension Activities:

Divide the class into groups of five. Assign each student in a group a different Related Reading to read. Then have students share what they learned with their group.