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Crystallization

Objective

To set up an experiment which visually demonstrates sugar crystallization. From this, we want to determine a material from which to start the crystallization in order to create the "best" crystals.

Difficulty

Procedure: Easy

Concept: Medium

Concept

For this experiment, it is recommended (not necessarily required) to have a basic understanding of high-school chemistry. To perform a sugar crystallization, most experiments involve saturating water with sugar. See supersaturation. For more background knowledge on sugar crystallization, click here.

Hypothesis:

On which material do you think would be best to begin growth of crystals? You might want to start off with nylon or cotton.

Materials:

• Water (1/4 L)
• Sugar (3/4 L)
• Large, clean glass jar
• String
• Stirring rod (or other stirring utensil)
• Pencil (long enough to be placed across the diameter of the glass jar
• Pan (for heating water-sugar solution)

Procedure:

• Pour water and sugar into a pan. Caution with boiling water. Adult supervision is required for boiling. Check out our safety guide.
• Pour sugar-water solution into the glass jar.
• Tie the string and let it dangle from the center of the pencil so that it almost touches the bottom of the jar.
• Keep stored and check daily. Make sure that it remains undisturbed.
• Repeat this process for different type strings.

Analysis

Which string seemed to hold the crystals best? Why do you think that is the case? Be sure to keep in mind that the string may not have a sole effect on the crystals forming on it.

Conclusion

Do you think you can find other materials which would serve better than the ones used in your initial experiments? What other factors do you think affected the crystallization (room temperature, water impurities, etc.)?

Extensions

What other factors do you think affect the growth of crystals? Do you think there is a way to speed up the crystallization process? Try looking into seed crystals to improve the results of the experiment. What other solute could you use to make crystals?