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Crystal Ball
Recommended Grade Level(s):
Appropriate for: K–12
Time Requirements:
Activity Time: 10 minutes. Preparation: 15 minutes
Teaching Topics & Concepts:
• To illustrate the crystallization of a supersaturated solution.
• Exothermic crystallization.
• Evidence, models and explanation, constancy, change, and measurement.
• Structure and properties of matter, conservation of energy and increase in
disorder, interactions of energy and matter.
• Enthalpy, entropy, and free energy.
Background:
On a cold winter day, those reusable instant hand warmers we buy at gas sta-
tions provide a little relief. Even football players use them during cold-weather
games. Once the warmer is activated, it starts the formation of crystals from a
supersaturated solution. The process is exothermic, generating heat. This effect
can be reproduced in the lab to offer more control over the process and make
scientific observations. This activity is a great way to introduce students to the
exciting and challenging world of crystals and real-world applications.
Materials:
• Sodium acetate trihydrate, NaC2H3O2•3H2O
• Round bottom flask or Erlenmeyer flask with a rubber stopper
• Hot plate or Bunsen burner
• Wash bottle
• Distilled water
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Safety
• Sodium acetate is a skin, eye, and respiratory irritant. Wear chemical splash goggles,
chemical-resistant gloves, and a chemical-resistant apron.
• Read the SDS sheets for all chemicals before using them.
• Wash hands thoroughly with soap and water before leaving the laboratory.
• Follow all laboratory safety guidelines.
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