Incorporate science and math into your Valentine’s Day classroom celebration this year with a crystal hearts science experiment. This simple and easy salt crystal experiment is a great way to demonstrate how crystals form and to introduce the subjects of crystallization, solubility, and chemical reactions. This Valentine’s science experiment uses easy-to-find supplies and can be completed with small groups or with the whole class. Your students will enjoy the results – their very own crystal heart for Valentine’s Day!

Materials Needed:
Colored pipe cleaners
String
Pencils
Wide-mouth jars (beakers, coffee mugs, mason jars, milk cartons)
Borax
Boiling water

Before You Begin:
Before you start your crystal experiment, introduce the topic of crystallization with these key vocabulary words and concepts:

• Chemical Reaction: a process where a substance changes to form a different substance.
  • Chemical reactions happen everywhere, even in your own body (for example, when rust forms). Some changes can happen quickly, and some happen slowly over time depending on the substances.
• Solubility: The amount of a substance that will dissolve in another substance (or become a part of another substance).
• Crystallization: A process by which crystal molecules fit together to form a repeating pattern and unique shape.
  • Most crystals form from liquids cooling and hardening.
  • Crystals can form in different shapes (cubic, hexagonal, tetragonal, trigonal and more).
• Crystallography: The science of the study of crystals and how they form.

Steps:

1. Shape each pipe cleaner into a heart.
2. Tie the string around each pipe cleaner and attach it to a pencil. Measure the depth and height of the jar and cut the string to a slightly shorter measurement.
3. Mix solution of boiling water and borax in a glass jar (3 tablespoons of borax to 1 cup of water). Students can measure the borax, but the teacher must pour the water and closely observe small groups of students to prevent any burns!
4. Lower the pipe cleaner heart into the solution and place the pencil over the top of the jar.
5. Wait 24 hours and pull out your crystals! (It works best to complete the activity at the end of the day and have students come back to check on the crystals in the morning.)
6. Tie a pink or red ribbon around your hearts and create a hanging Valentine’s Day decoration!

Reflections

1. Why did the water have to be boiling?
2. What shape are the crystals?
3. What would happen if you put your heart crystal into a pot of boiling water? (It would re-dissolve.)

Have students observe their crystal heart and record their observations in a journal. Ask students to describe the process of crystallization in their journals using key vocabulary.

For more lessons on chemical reactions, see this unit from ScienceWorks for Kids: Simple Chemistry: When Substances React Chemically (grades 4–6) 

For more hands-on science activities, download these sample printables from Science Lessons and Investigations for grades 1-6. 

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Heather Foudy is a certified elementary teacher with over 7 years’ experience as an educator and volunteer in the classroom. She enjoys creating lessons that are meaningful and creative for students. She is currently working for Evan-Moor’s marketing and communications team and enjoys building learning opportunities that are both meaningful and creative for students and teachers alike.