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Growing Crystals

STEM To-Go Activity

Create crystals using salt and look closely at molecules.



  • Clear Cup

  • Elastic Band

  • Paper Clip

  • String

  • Straw

  • Salt

  • Warm Water

  • Spoon

  • Magnifying Glass

  • Observation Log (Appendix B)

Activity Instructions

1. Tie the middle of the string to the paper clip. The two ends should hang down.

2. Slide the paper clip onto the middle of the straw. 3. Pour some warm water into the cup until it is about 3⁄4 full. 4. Add 5 spoonfuls of salt to the water and stir until the salt mostly disappears.

5. Bend the ends of the straw and place it on the cup.

6. Stretch the rubber band around the straw and cup. 7. Place the cup in a quiet place for a couple of days. Record what you see each day in your Observation Log. (Appendix B) 8. Repeat the experiment with different amounts of salt.

Tip: As your crystal grows, use the magnifying card to observe what you see.

Keep in Mind While Observing:

What shapes do you see as the crystals form?

Do all crystals have the same shape and structure?

The Science Behind It All

How do the crystals forms?

The salt that we add to our food is made up of tiny particles called molecules. Solid salt forms a crystal because the molecules are arranged in a repeating pattern. Other examples of crystals are sugar, snowflakes, and diamonds.

In this activity, the salt is dissolved in water to make a solution. When the water evaporates, salt crystals form.

Activity Sheet

Observation Log


Extra Resources


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